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Drug Half-Life, Steady State, and Recommended Sample Collection Time
This Topic Brief provides the drug half-life and time to steady state for many therapeutic drugs. It also provides guidance on how to use this information when monitoring therapeutic drugs.
See also Related tests (108) Related guides (1) Test guide list

Topic Brief

 

Therapeutic Drug Monitoring

Drug Half-Life, Steady State, and Recommended Specimen Collection Time

 

Therapeutic drug monitoring (TDM) is commonly used to determine whether measured drug levels are within the therapeutic range.1,2 The therapeutic range is the concentration range over which, for most patients, the probability of a beneficial clinical response is high and the probability of toxic effects is low. TDM is particularly useful for monitoring drugs that are used long-term and have a narrow therapeutic range.1,2 TDM is also useful to help detect and monitor drug-drug interactions and help identify inadequate patient adherence to prescribed therapy as a cause of poor treatment response.1,2

After administering a drug at regular intervals and fixed dose, the most clinically useful time to collect a specimen for TDM is at steady state. At a steady state, the drug has reached an equilibrium between equal rates of adsorption and elimination.1 The time required to reach steady state depends on the drug’s elimination half-life, which is determined by the drug’s metabolism and excretion rates.

The number of half-lives to reach steady state depends on the

  • Kinetics of elimination: most drugs follow first-order kinetics with constant proportion of drug eliminated dependent on plasma concentration.
  • Compartment model of distribution: most drugs follow a 1-compartment distribution model and are rapidly and evenly distributed throughout the body.1,3

Under these conditions, steady state concentrations of drug are usually reached within 5 half-lives assuming that therapy was not initiated with a high loading dose for an immediate therapeutic response.4

Steady state concentrations of drugs may deviate from 5 half-lives if they

  • Follow non–first-order kinetics5 (eg, phenytoin, ethanol, and aspirin [salicylates at high concentration] follow zero-order [saturation] kinetics; elimination is independent of plasma concentration; thus, increases in dose may not correspond to increases in plasma concentrations6).
  • Have multicompartment distribution models; the drug initially enters plasma and then distributes at different rates between plasma and tissues (eg, aminoglycoside antibacterials: gentamicin, amikacin, and tobramycin7 [2-compartment] and antiarrhythmic amiodarone [multiple compartments]).3
  • Undergo extensive first-pass metabolism in the liver3

Except in medical emergencies, a monitored drug should be allowed to reach a new steady state following a dosage change, the addition or discontinuation of a co-administered drug that affects the first drug’s metabolism, or both.1 Similarly, a period of at least 5 half-lives must elapse to almost completely eliminate a discontinued drug that had reached steady state.1

Once steady state has been reached, drug concentrations in peak and/or trough serum specimens may be determined. Peak specimens are typically collected 2 to 3 hours after an oral dose2; 30 to 60 minutes after an intravenous dose2; 2 to 4 hours after an intramuscular dose2; or 1 to 1.5 hours after an intranasal dose.8,9 Trough specimens are collected just before administration of the next scheduled dose. TDM of aminoglycoside antibiotics, such as gentamicin, tobramycin, and amikacin, requires determination of both peak and trough concentrations for multiple daily dosing regimens.3,7 For most other drugs, only trough concentrations are measured.2

The Table contains, unless otherwise specified, estimates of drug half-life and steady state specimen collection times, and test codes for drugs commonly prescribed as immediate-release formulations and excluding time-release and long-acting formulations. The pharmacokinetics of each drug may vary with patient age, sex, weight, clinical status, and the presence of other drugs.

Test codes for blood-based drug screening panels are provided for use when (a) assays for the individual drugs are unavailable to determine half-life and steady state or (b) individual drug assay test results and/or clinical presentation suggests nonadherence to prescribed therapy (eg, drug test result is "not detected" or clinical presentation suggests use of unprescribed drugs).

All test codes are linked to the Quest Diagnostics: Test Directory for more information. Parameters provided in the table provide generalized guidance and are not meant to replace patient assessment and clinical judgment.

Table. Drug Half-life and Time to Steady Statea [A-F] [G-N] [O-Z]

Drug name Half-life Time to steady state Test code
Acetaminophen 2-3 hours10 adult 10-20 hours10   201
  1-3 hours10 child      
Alprazolam 11 hours11 adult 5-6 days12   4741
  16 hours11 elderly    
    prolonged in obesity and hepatic disease; longer by 25% in Asian vs White persons    
Amikacin 2-3 hours10   10-15 hours10   236
          8584
          250
Amiodarone 26-107 days13   not applicable   36721
  61 days13 N-desethylamiod-arone    
Amitriptyline 10-28 hours10 amitriptyline 2-6 days10 amitriptyline 423
  18-93 hours10 nortriptyline, adult 4-21 days10 nortriptyline, adult 94031 (panel)c,d
  14-22 hours10 nortriptyline, child 3-5 days10 nortriptyline, child
Amoxapine 8-30 hours13   not given   94031 (panel)c,d
Amoxicillin 3.7 hours13 full-term neonates 2 days14   94095
  1-2 hours13 infants, children    
  0.7-1.4 hours13 adults    
Amphetamine 9.0-12.7 hours13 children 6-12 years, D-amphetamine not given   14744
  10.0-15.3 hours13 children 6-12 years, L-amphetamine    
  10.0-12.4 hours13 adults, D-amphetamine    
  11.7-15.3 hours13 adults, L-amphetamine    
Aripiprazole 75 hours15   14 days15   15922
          94529 (panel)c,e
Baclofen 1.5 hours13 intrathecal not given   36662
  5.7 hours13 tablet    
  5.5 hours13 granules    
Bismuth 21-72 days13 terminal half-life not given   5374
Buprenorphine 2.2 hours13 intravenous not given   93031 (panel)c,d
  31-35 hours16 sublingual tablet      
Bupropion 21 hours17   8 days17   8592
          94031 (panel)c,d
          94032 (panel)c,f
Brivaracetam 8-9 hours18   not given   39887
Caffeine 4-5 hours10 adult not applicable (high variability)   305
  65-102 hours10 neonate    
Carbamazepine 10-20 hours10 adult 2-6 days10 adult 26513
  8-19 hours10 child 2-4 days10 child 6071
    7933
      18948
      18949
          36676
Carbidopa 2 hours13   not given   3388
Carisoprodol 2 hours13 carisoprodol not applicable   312
  8 hours13 meprobamate    
Chlordiazepoxide 6-25 hours13 normal liver and kidney function not given   91123
  5-30 hours13 end-stage renal disease    
  30-63 hours13 liver cirrhosis    
Chlorpromazine 7-119 hours19   not applicable   882
          94529 (panel)c,e
Citalopram 24-48 hours13   1-2 weeks20   10184
          94031 (panel)c,d
Clomipramine 32 hours13 clomipramine 3 weeks21   30013
  69 hours13 norclomipramine     94031 (panel)c,d
  69 hours13 desmethylclomipramine    
Clonazepam 17-60 hours13 adult 5-7 days13   340
  22-33 hours13 child    
Clozapine 12 hours13 5-10 days23   1769
  22.5 hours22 norclozapine     94529 (panel)c,e
Codeine 3-4 hours13   not given   19483 (panel)c,g
Cycloserine 10 hours13 normal renal function not given   92020
Cyclosporine 6-27 hours10 influenced by underlying disease 2-6 days10   10720
          10719
          8812
          15220
Desalkylflurazepam 48-120 hours13   not given   70071 (panel)c,h
Desipramine 15-24 hours13   not given   412
          94031 (panel)c,d
Desmethylsertraline 62-104 hours24   7 days24   8871
Diazepam 20-48 hours25 adult 5-14 days26   90853
  18 hours25 child    
  100 hours25 nordiazepam    
  prolonged in hepatic disease    
Digitoxin 4-6 days10   4 weeks27   417
Digoxin 26-48 hours10 adult 7-19 days28   418
  12-48 hours10 child    
  prolonged in renal disease    
Disopyramide 7 hours10 adult 24-48 hours10   416
  3-4 hours10 child    
  prolonged in renal disease    
Doxepin 12-24 hours10 adult 2-5 days10 adult 826
  30-50 hours10 child 6-13 days10 child 94031 (panel)c,d
Doxycycline 15-25 hours13   not given   94093
Duloxetine 8-17 hours29   3 days29   16823
          94031 (panel)c,d
Escitalopram 27-32 hours13   7-10 days30   15857
          94031 (panel)c,d
Eslicarbazepine 13-20 hours13   4-5 days31   92139
Ethambutol 2.5-3.6 hours13   not given   92018
  7-15 hours13 end-stage renal disease    
Ethosuximide 50-60 hours10 adult 8-12 days10 adult 214
  30 hours10 child 6-10 days10 child
Everolimus 18-35 hours10   4-7 days10   18883
Felbamate 20-23 hours13   5 days32   3081
Fentanyl 2-4 hours13 injection not given   40065
  20-27 hours13 transdermal patch    
Flecainide 12-27 hours33 prolonged in renal disease 3-5 days33   5309
Fluconazole 20-50 hours34 adult 5-10 days34   94097
  15.2-25.0 hours34 child    
  54.2 hours34 neonate    
  prolonged in renal disease    
Flucytosine 3-5 hours35 adult 18-30 hours36   35692
  8 hours35 infant    
  prolonged in renal disease    
Fluoxetine 4-6 days13 chronic administration 4 weeks38   8389
  1-3 days13 acute     94031 (panel)c,d
  7-6 days13 cirrhosis    
Fluphenazine 13-58 hours19 hydrochloride 2 weeks39   92021
  3-4 days19 enanthate     94529 (panel)c,e
  5-12 days19 decanoate      
Fluvoxamine 15.6 hours13 adults 5-10 days37   30529
  17.4-25.9 hours13 elderly    
Fondaparinux 17-21 hours40 prolonged in renal disease 3 hours40   16103
Gabapentin 5-9 hours10 adult 1-2 days10 adult, child 3557
  4-6 hours10 child    
Gentamicin 2-3 hours10 prolonged in renal disease 10-15 hours10   481
          8582
          444
          8575
Haloperidol 14-41 hours19 lactate 3-9 daysb lactate 564
  14-28 days19 decanoate not applicable decanoate 94529 (panel)c,e
Heparin Anti-Xa (Low Molecular Weight Heparin) 4.5-7.0 hours41 subcutaneous injection 2-4 days41   30292
    prolonged in renal disease    
Heparin Anti-Xa (Unfractionated Heparin) 30-150 min40 dose dependent 6 hours40   30292
Hydrocodone 3.3-4.4 hours13   not given   19483 (panel)c,g
Hydromorphone 2-3 hours13 immediate-release not given   19483 (panel)c,g
  11 hours13 extended-release    
Hydroxychloroquine 40-50 days42   not given   3333
Ibuprofen 2-4 hours10 adult 24-48 hours10   5136
  1-3 hours10 child    
Imipramine 6-18 hours13   2-5 days10   887
          94031 (panel)c,d
Isoniazid 1-2 hours19 adult, slow inactivator (50% of Black and White individuals) 6-8 weeks43,44   577
  2-7 hours19 adult, rapid inactivator (majority of Asian and Inuit individuals)    
Itraconazole 16-28 hours45 after single dose 15 days45   94092
  34-42 hours45 with repeated dosing    
  prolonged in hepatic disease    
Lacosamide 13 hours13   not given   16262
Lamotrigine 24-34 hours10 adult 3-10 days10 adult, child 22060
  ~30 hours10 child    
Leflunomide 14-18 days13   not given   18865
Levetiracetam 6-8 hours10 adult 2 days10 adult 15142
  5-7 hours10 child 1-2 days10 child 36330
  prolonged in renal disease
Levodopa 3.5 hours13   not given   3388
  1.5 hours13 when administered with carbidopa    
Lidocaine   1-2 hours10 prolonged in hepatic disease 8-10 hours10   605
Lithium 24 hours10 average in young healthy subjects 3-4 days10   613
    varies with renal function    
Lorazepam 18 hours13 children 2-12 years 5 days13 capsules 70071 (panel)c,h
  42 hours13 neonates    
  28 hours13 adolescents    
  18 hours13 end stage renal disease    
  12 hours13 tablets, adults    
  20.2 hours13 capsules, adults
    
Loxapine 4-12 hours13   not given   94529 (panel)c,e
Meperidine 2-5 hours19   not given   411
Meprobamate 6-16 hours13   not given   312
Mesoridazine 24-48 hours46   not given   94529 (panel)c,e
Methotrexate 3-10 hours10,19 psoriasis, rheumatoid arthritis, or low-dose therapy adult 24-48 hours10 adult, child 648
  8-15 hours19 high-dose therapy, adult    
  5-9 hours10 child    
Midazolam 2-6 hours13   not given   70071 (panel)c,h
Mirtazapine 20-40 hours10   not given   30348
          94031 (panel)c,d
Molindone 1.5 hours13   not given   94529 (panel)c,e
Morphine 2-4 hours13 immediate release not given   6215
  11-13 hours13 extended release    
Mycophenolic acid  8-18 hours10 adult not applicable   10662
  variable10 child    
Nortriptyline 18-93 hours10 adult 4-21 days10 adult 272
  14-22 hours10 child 3-5 days10 child 423
          94031 (panel)c,d
Olanzapine 21-54 hours47 adult ≤65 years 7 days47   70073
  32-81 hours47 adult >65 years     94529 (panel)c,e
Oxazepam 2.8-5.7 hours   not given   70071 (panel)c,h
Oxcarbazepine 8-15 hours10 10-hydroxycarbazepine metabolite, adult 2 days10 adult 36637
  5-9 hours10 10-hydroxycarbazepine metabolite, child 1 day10 child
Oxycodone 3-5 hours48   >24 hours48   18885
Paliperidone 23 hours13 oral not given   91895
  25-159 days13 intramuscular, dose dependent    
Paroxetine 12-44 hours10   4-14 days49   94031 (panel)c,d
Pentobarbital 15-50 hours13   not applicable   700
Perampanel 105 hours50   2-3 weeks50   93744
Phenobarbital 81-117 hours10 adult 17-24 days10 adult 708
  40-70 hours10 child 8-15 days10 child 751
    7311
      7312
Phenytoin 12-36 hours10 adult 5-7 days10 adult 713
  7-29 hours10 child 2-5 days10 child 3189
    7311
      7312
Posaconazole 34 hours10   7 days10   94010
Pregabalin 6 hours51   1-2 days51   18866
Primidone 6-12 hours10 adult 30-40 hours10 adult 751
  4-6 hours10 child 20-30 hours10 child 7312
Procainamide 2-5 hours10   11-20 hours10   743
  6 hours19 N-acetyl procainamide not applicable N-acetyl procainamide
Propafenone 2-10 hours13 extensive metabolizer (>90% of population) 4-5 days52   6278
  10-32 hours13 poor metabolizer (<10% of population)    
Protriptyline 54-92 hours13   not given   94031 (panel)c,d
           
Pyrazinamide 9-10 hours13   6-8 weeks43,44   92184
Quinidine 5-12 hours10 adult 30-35 hours10 adult 766
  3-7 hours10 child varies with age10 child
Quetiapine 6 hours53   2 days53   35299
          94529 (panel)c,e
Rifampin 1-5 hours10 adult 6-8 weeks43,44 adult 92017
  3 hours10 child varies with age10 child
Risperidone 3 hours54 fast metabolizer, risperidone 1 day54 fast metabolizer, risperidone

2339

94529 (panel)c,e
  21 hours54 fast metabolizer, 9-hydroxyrisperidone 5-6 days54 fast metabolizer, 9-hydroxyrisperidone  
  20 hours54 slow metabolizer, risperidone 5 days54 slow metabolizer, risperidone  
  30 hours54 slow metabolizer, 9-hydroxyrisperidone not applicable slow metabolizer, 9-hydroxyrisperidone
  prolonged in renal disease  
Rivaroxaban 5-9 hours13   not given   90981
  11-13 hours13 elderly    
Rufinamide 6-10 hours55   2 days55   16296
Salicylate 2-3 hours10 adult, child 10-23 hours10 adult 805
  increases with higher doses 10-15 hours10 child
Sertraline 26 hours56   1 week56   8871
Sirolimus (rapamycin) 46-78 hours10 influenced by underlying disease 5-7 days10  

3671

13232
Streptomycin 4-10 hours13 newborns not given   92060
  2.0-4.7 hours13 adults, prolonged in renal disease    
Tacrolimus (FK506) 4-35 hours10 adult 2-6 days10 adult 70007
  4-12 hours10 child not applicable child 13232
    influenced by underlying disease      
Temazepam 9.5-12.4 hours13   not given   70071 (panel)c,h
Theobromine 7 hours57   not given   876
Theophylline 5-6 hours10 adult 15-55 hours10 adult 878
  4 hours10 child 5-40 hours10 child
  influenced by underlying disease  
Thiocyanate 3 days13   not applicable   879
Thioridazine 24 hours13   not given   94529 (panel)c,e
Thiothixene 24 hours13   not given   94529 (panel)c,e
Tiagabine 7-9 hours13   2 days58   30333
  4-7 hours13 with concomitant CYP3A4 inducers    
Tobramycin 2-3 hours10   5-15 hours10   888
          8576
          890
          8577
Topiramate 20-30 hours10 adult 3-5 days10 adult 30965
  12-24 hours10 child 2-4 days10 child
  prolonged in renal disease
Trazodone 7-10 hours10   4 days59   4732
          94031 (panel)c,d
Triazolam 1.5-5.5 hours13   not given   70071 (panel)c,h
Trifluoperazine 24 hours13   not given   94529 (panel)c,e
Trimipramine 16-40 hours13   not given   94031 (panel)c,d
Valproic Acid 8-15 hours10 adult 2-4 days10 adult, child 916
        3314
  8-11 hours10 child     6651
Vancomycin 5-11 hours10 adult 1-2 days10 adult, child 917
  3-10 hours10 child     8578
        8579
        5406
Venlafaxine 3-7 hours60   3 days60   94031 (panel)c,d
Vilazodone 25 hours13   not given   94031 (panel)c,d
Voriconazole 6-9 hours10 increases with dose 5-7 days13,61-63   94096
Vortioxetine 66 hours64   2 weeks64   94031 (panel)c,d
Warfarin 20-60 hours13 patient-specific 5-13 daysb   936
Ziprasidone 7 hours13 oral not given   17286
  2-5 hours13 intramuscular     94529 (panel)c,e
Zonisamide 50-70 hours10 adult 8-12 days10 adult 37852
  40-60 hours10 child 6-10 days10 child
a Data listed are for adults unless otherwise specified.
b Time to steady state was calculated by multiplying the half-life by 5.
c Test codes for blood-based drug screening panels are provided for use when (a) assays for the individual drugs are unavailable to determine half-life and steady state or (b) a patient is taking multiple antidepressants and antipsychotics.
d Panel includes amitriptyline, amoxapine, citalopram/escitalopram, clomipramine, desipramine, doxepin, duloxetine, fluoxetine, fluvoxamine, hydroxybupropion, imipramine, maprotiline, mirtazapine, nortriptyline, paroxetine, protriptyline, sertraline, trazodone, trimipramine, venlafaxine, vilazodone, and vortioxetine.
e Panel includes aripiprazole, chlorpromazine, clozapine, fluphenazine, haloperidol, loxapine, mesoridazine, molindone, olanzapine, quetiapine, risperidone, thioridazine, thiothixene, trifluoperazine, and ziprasidone.
f Panel includes amitriptyline, amoxapine, citalopram/escitalopram, clomipramine, desipramine, doxepin, desmethyldoxepin, duloxetine, fluoxetine, fluvoxamine, hydroxybupropion, imipramine, maprotiline, mirtazapine, nortriptyline, paroxetine, protriptyline, sertraline, trazodone, trimipramine, venlafaxine, vilazodone, and vortioxetine.
g Panel includes codeine, hydrocodone, hydromorphone, morphine, and oxycodone.
h Panel includes alprazolam, alpha-hydroxyalprazolam, alpha-hydroxytriazolam, chlordiazepoxide, clonazepam, desalkylflurazepam, diazepam, lorazepam, midazolam, norchlordiazepoxide, nordiazepam, oxazepam, temazepam, and triazolam.

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  34. Diflucan® (fluconazole tablets). Product information. Roerig Division of Pfizer Inc. November, 2021. Accessed April 7, 2025. https://labeling.pfizer.com/showlabeling.aspx?id=575

  35. Ancobon® (flucytosine). Product information. Valeant Pharmaceuticals North America LLC. February, 2019. Accessed April 7, 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/017001s033lbl.pdf

  36. Goodwin ML, Drew RH. Antifungal serum concentration monitoring: an update. J Antimicrob Chemother. 2008;61(1):17-25. doi:10.1093/jac/dkm389

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  38. Wilens TE, Cohen L, Biederman J, et al. Fluoxetine pharmacokinetics in pediatric patients. J Clin Psychopharmacol. 2002;22(6):568-575. doi:10.1097/00004714-200212000-00006

  39. Glazer WM, Friedhoff LT, Marder SR, et al. The determination of the steady-state pharmacokinetic profile of fluphenazine decanoate by gas chromatography/mass spectrometry detection. Schizophr Res. 1992;8(2):111-117. doi:10.1016/0920-9964(92)90026-2

  40. Garcia DA, Baglin TP, Weitz JI, et al. Parenteral anticoagulants: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2012;141(2 Suppl):e24S-e43S. doi:10.1378/chest.11-2291

  41. Lovenox (enoxaparin sodium) injection. Product information. sanofi-aventis US LLC. December, 2021. Accessed April 7, 2025. https://products.sanofi.us/Lovenox/lovenox.pdf

  42. Sovuna® (hydroxychloroquine sulfate). Prescribing information. ANI Pharmaceuticals. October, 2024. Accessed March 20, 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/214581s011lbl.pdf

  43. Ruslami R, Nijland HM, Alisjahbana B, et al. Pharmacokinetics and tolerability of a higher rifampin dose versus the standard dose in pulmonary tuberculosis patients. Antimicrob Agents Chemother. 2007;51(7):2546-2551. doi:10.1128/AAC.01550-06

  44. McIlleron H, Wash P, Burger A, et al. Determinants of rifampin, isoniazid, pyrazinamide, and ethambutol pharmacokinetics in a cohort of tuberculosis patients. Antimicrob Agents Chemother. 2006;50(4):1170-1177. doi:10.1128/AAC.50.4.1170-1177.2006

  45. Sporanox® (itraconazole). Product information. Janssen Pharmaceuticals Inc. December, 2019. Accessed April 7, 2025. https://www.janssenlabels.com/package-insert/product-monograph/prescribing-information/SPORANOX-Capsules-pi.pdf

  46. Serentil (mesoridazine besylate) Tablets, Injection, Oral Solution, USP. Prescribing information. Novartis. Accessed April 7, 2025. https://www.accessdata.fda.gov/drugsatfda_docs/nda/2001/16-774S073.pdf

  47. Zyprexa (olanzapine). Prescribing information. Eli Lilly and Company. April, 2021. Accessed April 7, 2025. https://pi.lilly.com/us/zyprexa-pi.pdf

  48. Ordóñez Gallego A, González Baron M, Espinosa Arranz E. Oxycodone: a pharmacological and clinical review. Clin Transl Oncol. 2007;9(5):298-307. doi:10.1007/s12094-007-0057-9

  49. Bourin M, Chue P, Guillon Y. Paroxetine: a review. CNS Drug Rev. 2001;7(1):25-47. doi:10.1111/j.1527-3458.2001.tb00189.x

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  51. Bockbrader HN, Radulovic LL, Posvar EL, et al. Clinical pharmacokinetics of pregabalin in healthy volunteers. J Clin Pharmacol. 2010;50(8):941-950. doi:10.1177/0091270009352087

  52. Rythmol (propafenone hydrochloride). Prescribing information. GlaxoSmithKline. March, 2013. Accessed April 7, 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/019151s012lbl.pdf

  53. Quetiapine tablet, film coated. Prescribing information. Teva Pharmaceuticals. August, 2022. Accessed March 20, 2025. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=c1d4ef59-bf58-44fe-9b46-1af42e2f7f8b&type=display#section-12

  54. Risperdal® (risperidone). Product information. Janssen Pharmaceuticals Inc. February, 2021. Accessed April 7, 2025. https://www.janssenlabels.com/package-insert/product-monograph/prescribing-information/RISPERDAL-pi.pdf

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  56. Zoloft (sertraline hydrochloride) tablets, for oral use Zoloft (sertraline hydrochloride) oral solution. Prescribing information. Viatris. August, 2023. Accessed April 2, 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/019839s108,20990s062lbl.pdf

  57. Lelo A, Birkett DJ, Robson RA, et al. Comparative pharmacokinetics of caffeine and its primary demethylated metabolites paraxanthine, theobromine and theophylline in man. Br J Clin Pharmacol. 1986;22(2):177-182. doi:10.1111/j.1365-2125.1986.tb05246.x

  58. Gabitril® (tiagabine hydrochloride) tablets. Cephalon. Updated April 2009. Accessed April 3, 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/020646s016lbl.pdf

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  60. Effexor XR® (venlafaxine extended-release) capsules, for oral use. Prescribing information. Viatris. Updated August 2023. Accessed April 3, 2025. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=c848a5d8-ba94-4c84-80e3-0bf35fb8e32e&type=display

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Content reviewed 4/2025

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6651 - Valproic Acid, Total and Free

Valproic acid is used as an anticonvulsant to treat certain types of seizures, to prevent migraine headaches, and to treat various psychiatric illnesses such as bipolar disorder and aggression. Drugs that compete for protein-binding sites with Valproic Acid, can increase the concentration of Valproic Acid. Therapeutic drug monitoring is useful to optimize dose. Measurement of the free concentration is useful if toxicity is suspected.

201 - Acetaminophen

Acetaminophen is an analgesic agent that may be hepatotoxic when ingested in quantities exceeding 150 mg/kg.

917 - Vancomycin

Vancomycin is an antibiotic used in the treatment of serious bacterial infections, especially methicillin-resistant staphylococci. Vancomycin is also used in treatment for penicillin-allergic patients who cannot receive or have failed to respond to other drugs, including the penicillins and/or cephalosporins and for other infections caused by vancomycin-susceptible organisms.

272 - Nortriptyline

Nortriptyline is a tricyclic antidepressant. Therapeutic drug levels are monitored to assist the physician assessing therapeutic response and to avoid toxicity.

6215 - Morphine, Free (Unconjugated), Serum

Therapeutic drug monitoring and confirmation of screen-positive results. Morphine is an active component of Depodur, Roxanol, etc. Serum half-life is 1.3 to 6.7 hours.

94093 - Doxycycline

The concentration of antimicrobial agents in body fluids, most notably serum or plasma, are used to regulate therapy to ensure effective dosing (especially with oral agents where GI absorption is in question), to monitor accumulation to help minimize toxicity, and to help evaluate the pharmacokinetics of new agents. Both peak and trough levels obtained immediately after dosing or immediately prior to new dosing, respectively, may be monitored.

15142 - Levetiracetam

Levetiracetam is an anticonvulsant used as adjunct therapy to treat adult partial seizures. As multiple anticonvulsants are administered, it is important to monitor its level to (1) optimize therapy, (2) assure compliance, and (3) to avoid toxicity.

36721 - Amiodarone

Amiodarone is an antiarrythmic drug. Therapeutic drug monitoring is useful to monitor compliance and avoid toxicity.

7933 - Carbamazepine and Metabolite, Free/Bound/Total

Carbamazepine and its metabolite (10,11-carbamazepine epoxide) are widely used for control of generalized tonic-clonic, partial-onset, complex and mixed seizure disorders. The metabolism of carbamazepine in epileptic patients has several different pathways that can be altered when the patient is co-medicated with other anticonvulsants and, therefore, it's therapeutic level should be monitored along with its metabolite in their free and protein bound states.

214 - Ethosuximide

Ethosuximide is an anticonvulsant used to treat seizures. Ethosuximide levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

423 - Amitriptyline

The tricyclics are used to treat depression. Nortriptyline is an active metabolite of Amitriptyline. Therapeutic drug levels are monitored to assist the physician assessing therapeutic response and to avoid toxicity.

312 - Carisoprodol and Metabolite, Serum, Plasma or Blood

Test is for Therapeutic Drug Monitoring (scope: Carisoprodol and Meprobamate Metabolite).

8578 - Vancomycin, Peak

Vancomycin is an antibiotic used in the treatment of bacterial infections, especially methicillin-resistant staphylococci. Vancomycin is also used in treatment for penicillin-allergic patients who cannot receive or have failed to respond to other drugs, including the penicillins and/or cephalosporins and for other infections caused by vancomycin-susceptible organisms.

92021 - Fluphenazine, Serum/Plasma

Therapeutic drug monitoring.

5309 - Flecainide

Monitoring the Flecainide concentration is used to assure compliance and avoid toxicity of this cardiac drug used to treat ventricular tachycardia and premature contractions.

90853 - Diazepam and Metabolite

Therapeutic drug monitoring of anxiolytic drug. Nordiazepam is the active metabolite of the parent drug. Elimination half-life is 20-90 hours.

444 - Gentamicin, Peak and Trough

Gentamicin is an aminoglycoside antibiotic used in the treatment of gram positive and gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and Staphylococcus. Gentamicin is potentially nephrotoxic and ototoxic and serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

481 - Gentamicin

Gentamicin is an aminoglycoside antibiotic used in the treatment of gram-positive and gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and Staphylococcus. Gentamicin is potentially nephrotoxic and ototoxic. Serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

887 - Imipramine

Imipramine is a tricyclic antidepressant drug used to treat depression. Therapeutic drug monitoring is used to optimize dose and to avoid toxicity.

3081 - Felbamate

Felbamate is an antiepileptic drug used to treat patients with a variety of types of seizures. Therapeutic drug monitoring is useful to optimize dose and avoid toxicity.

8582 - Gentamicin, Peak

Gentamicin is an aminoglycoside antibiotic used in the treatment of gram-positive and gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and Staphylococcus. Gentamicin is potentially nephrotoxic and ototoxic. Serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

416 - Disopyramide

Disopyramide is useful in treating patients with cardiac arrhythmias and tachcardia. Therapeutic drug monitoring is useful to optimize dose and avoid toxicity.

8576 - Tobramycin, Peak

Tobramycin is an aminoglycoside antibiotic used in the treatment of gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and also Staphylococcus. Tobramycin is potentially nephrotoxic and ototoxic and serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

8577 - Tobramycin, Trough

Tobramycin is an aminoglycoside antibiotic used in the treatment of gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and also Staphylococcus. Tobramycin is potentially nephrotoxic and ototoxic and serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

94010 - Posaconazole

The antifungal drug posaconazole is indicated for prophylaxis of invasive aspergillus and candida infections in severely immunocompromised patients. It may also be used in the treatment of oropharyngeal candidiasis refractory to itraconazole and fluconazole. The chronic nature of fungal infections demands constant monitoring of posaconazole levels within a patient to ensure that adequate therapeutic levels of the drug are administered, absorbed and subsequently excreted.

94097 - Fluconazole

Fluconazole is commonly used in the treatment of various types of fungal infections. Due to the fact it is readily soluble in water it can be administered in relatively large amounts to patients. Measurement of serum drug levels may be helpful to optimize drug dosing regimens, particularly where there is non-compliance, concern about drug interactions, pharmacokinetic variability, or suspected toxicity.

766 - Quinidine

Quinidine is used in the treatment of acute and chronic supraventricular arrhythmias and ectopic rhythm disturbances. Quinidine clearance can be altered by changes in plasma proteins and in renal and/or hepatic dysfunction. Both quinidine and the related isomer quinine possess antimalarial schizonticide activity. Quinidine levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

36712 - Sirolimus, LC/MS/MS

Sirolimus is an immunosuppressant drug used to prevent organ graft rejection. Therapeutic drug monitoring is used to optimize dose and avoid toxicity. Peak concentrations are reached in 2 hours following oral administration. Elimination half-life in males is approximately 72 hours; in females approximately 61 hours.

10719 - Cyclosporine A Peak (2 Hour), Blood

Cyclosporine (Cyclosporin A) is an immunosuppressant therapeutic agent used in the prevention of organ graft rejection. Clinical measurement of blood levels is required due to the inter-individual variability of metabolism as well as the toxicity associated with excessive dosage.

30013 - Clomipramine

Clomipramine and its active metabolite, norclomipramine are antidepressant drugs. Therapeutic drug monitoring is useful to optimize dose and to avoid toxicity.

30529 - Fluvoxamine, Serum/Plasma

Therapeutic drug monitoring.

2339 - Risperidone and Metabolite

Therapeutic drug monitoring for effective therapy. Risperidone is rapidly converted into its hydroxy metabolite in the liver. Peak concentration of risperidone occurs in about 1 hour following oral administration and for 9-hydroxyrisperidone the peak level is reached at 3 hours (17 hours for poor metabolizers). The elimination half-life of risperidone is 3 hours (20 hours for poor metabolizers), and is 21 hours of hydroxyrisperidone (30 hours for poor metabolizers).

15220 - Cyclosporine A Trough, LC/MS/MS, Blood

Cyclosporine is a commonly used immunosuppressive drug in patients receiving transplants. LC/MS/MS methods have higher specificity for the parent compound than immunoassay. Therapeutic drug monitoring is useful to optimize dose and avoid toxicity. High cyclosporine levels can lead to nephrotoxicity; Low levels can lead to organ rejection following transplant. Peak concentrations are reached at around 3.5 hours after oral dosage. Elimination half-life is 10-27 hours.

564 - Haloperidol

Monitoring the haloperidol concentration is used to assure compliance and avoid toxicity of this antipsychotic drug.

879 - Thiocyanate

Thiocyanate is used as a biomarker for exposure to cyanides or cyanide-containing chemicals. This test is a serum-based assay that is primarily used to monitor cyanide levels in individuals receiving sodium nitroprusside infusion therapy for treatment of extreme hypertension. It can also be used to determine cyanide levels in individuals who have been exposed to certain industrial chemicals, cigarettes, or thiocyanate-containing foods [1].

Thiocyanate is a principal metabolite of cyanide, which accumulates in the blood and urine in response to cyanide exposure, cigarette smoking, industrial chemicals, and sodium nitroprusside infusion. Some industrial chemicals associated with increased thiocyanate levels include acetonitrile, acrylonitrile, and amygdalin. Symptoms of thiocyanate toxicity include confusion, hyperreflexia, convulsions, and metabolic acidosis [1].

This test may be helpful for patients, with normal renal function who are receiving long-term nitroprusside therapy for 7 days or more, as well as patients with renal insufficiency who are receiving nitroprusside therapy for any length of time. Patients with renal insufficiency are especially at risk for cyanide toxicity [2].

Note that the following drugs elevate thiocyanate and could interfere with test accuracy: antipyrine, acetoacetate, and phenacetin (and their sulfoxides in large concentrations); phenacetin and acetaminophen; and salicylic acid and its complexes.

References
1. Riedel K, et al. Thiocyanate in plasma and saliva (Biomonitoring Methods, 2013). In: Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area of the DFG, ed. The MAK-Collection for Occupational Health and Safety: Annual Thresholds and Classifications for the Workplace. Wiley-VHCA AG: Zurich, Switzerland; 2013;13:277-292.
2. Schulz Y. Clin Pharmacokinet.1984;9:239-251.

30333 - Tiagabine, Serum/Plasma

Therapeutic drug monitoring.

70007 - Tacrolimus, Highly Sensitive, LC/MS/MS

Tacrolimus is an immunosuppressant drug which has been shown to be effective for the treatment of rejection following transplantation.

340 - Clonazepam

Clonazepam is a benzodiazepine used as a tranquilizer. Clonazepam is used in treating patients with seizures and in reducing tardive dyskinesia. Therapeutic drug monitoring is useful to avoid toxicity.

648 - Methotrexate

Methotrexate is an antimetabolite used in the treatment of certain neoplastic diseases, psoriasis and rheumatoid arthritis. In combination with other chemotherapeutic agents, high dose methotrexate doses followed by leucovorin rescue may be effective in prolonging relapse-free survival in patients with non-metastatic osteosarcoma. Methotrexate levels are monitored to assess toxicity.

3314 - Valproic Acid, Free

Valproic acid is used as an anticonvulsant to treat certain types of seizures, to prevent migraine headahces, and to treat various psychiatric illnesses such as bipolar disorder and aggression. Drugs that compete from protein-binding sites with valproic acid, can increase the concentration of valproic acid. Measurement of the free concentration is useful if toxicity is suspected.

250 - Amikacin, Peak and Trough

Amikacin is an aminoglycoside antibiotic used in the treatment of gram-negative bacillary infections. Amikacin is potentially nephrotoxic and ototoxic and serial monitoring of serum levels provides information to maintain safe and therapeutic levels.

94092 - Itraconazole

The antifungal drug itraconazole is active in the treatment of aspergillosis, blastomycosis, histoplasmosis, sporotrichosis, and onychomycosis. It is a protein-bound drug and thus has negligible CSF penetration. It may also be utilized in the treatment of systemic candidiasis and cryptococcosis, especially when other drugs are contraindicated or ineffective. The chronic nature of fungal infections demands constant monitoring of itraconazole levels within a patient to ensure that adequate therapeutic levels of the drug are administered, absorbed and subsequently excreted

6278 - Propafenone

Propafenone is a cardiac drug for treating ventricular arrhythmias. Therapeutic drug monitoring is important to optimize dose, to assure compliance, and to avoid toxicity.

882 - Chlorpromazine

Chlorpromazine is a phenothiazine for treating psychosis and Tourett's syndrome. Monitoring it's level is important to optimize therapy, to avoid toxicity, and to assure compliance.

37852 - Zonisamide

Zonisamide is commonly used as an adjunct together with other conventional anticonvulsants. As multiple drugs are administered, it is important to monitor its level to optimize therapeutic effects, to assure compliance, and to avoid toxicity.

92139 - Eslicarbazepine

Monitoring eslicarbazepine is helpful to avoid toxicity and to use as a baseline for future therapy. There is no established reference range. Individual patient concentrations should be evaluated in context of patient's clinical condition and prior concentrations.

40065 - Fentanyl and Norfentanyl

Fentanyls are extensively used for anesthesia and analgesia. There are fentanyl transdermal patches available that are used in chronic pain management.

10720 - Cyclosporine A Panel (Trough, 1 Hour, 2 Hour Post)

Cyclosporine (Cyclosporin A) is an immunosuppressant therapeutic agent used in the prevention of organ graft rejection. Clinical measurement of blood levels is required due to the inter-individual variability of metabolism as well as the toxicity associated with excessive dosage.

236 - Amikacin

Amikacin is an aminoglycoside antibiotic used in the treatment of gram-negative bacillary infections. Amikacin is potentially nephrotoxic and ototoxic and serial monitoring of peak and trough serum levels provides information to maintain safe and therapeutic levels.

878 - Theophylline

Theophylline is used in the treatment of bronchial asthma as well as in the treatment of chronic obstructive pulmonary disease and episodes of prolonged apnea in pre-term infants. Theophylline levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

708 - Phenobarbital

Phenobarbital is an anticonvulsant used for the long-term treatment of generalized tonic-clonic (grand mal) seizures and cortical focal seizures. Phenobarbital levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

8584 - Amikacin, Peak

Amikacin is an aminoglycoside antibiotic used in the treatment of gram-negative bacillary infections. Amikacin is potentially nephrotoxic and ototoxic and serial monitoring of serum levels provides information to maintain safe and therapeutic levels.

418 - Digoxin

Digoxin is a cardiac glycoside derived from the digitalis plant. It is used to treat congestive heart failure and atrial dysrhythmias. Digoxin levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

605 - Lidocaine

Lidocaine direct injection or infusion is used in the emergency treatment of ventricular arrhythmias caused by acute myocardial infarction, open-heart surgery. It is also used for topical anesthesia administered as a gel or by injection. Lidocaine levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

1769 - Clozapine

Clozapine is an atypical antipsychotic agent. Norclozapine has minimal therapeutic activity.

35692 - Flucytosine, Serum/Plasma

Therapeutic drug monitoring.

94096 - Voriconazole

The antifungal drug voriconazole is commonly used in the treatment of various types of fungal infections. An increased fungal resistance to similar drugs of greater toxicity has promoted the use of voriconazole in treating infections caused by aspergillus and other fungal species. The chronic nature of fungal infections demands constant monitoring of voriconazole levels within a patient to ensure that adequate therapeutic levels of the drug are administered, absorbed and subsequently excreted.

22060 - Lamotrigine

Lamotrigine is an anticonvulsant drug used as adjunctive treatment for refactory partial seizures.

305 - Caffeine

Coffee, tea and other beverages may contain caffeine. Caffeine is a methylxanthine found in over the counter products and in prescription medications. Small premature infants with mild respiratory distress shortly after birth may be treated with theophylline or caffeine. In neonates, a significant amount of theophylline is converted to caffeine. Since the demethylation pathway of theophylline is relatively undeveloped, caffeine levels may be elevated. Caffeine clearance rates typically reach adult values at about 3-4 months of age.

36662 - Baclofen, Serum/Plasma

Therapeutic drug monitoring.

8871 - Sertraline and Desmethylsertraline, Serum/Plasma

Sertraline (Zoloft® ) is a psychiatric drug indicated for the treatment of major depression and obsessive-compulsive disorders. Its clinical efficacy is similar to that of the traditional antidepressants but are thought to be mediated through inhibition of serotonin reuptake in the brain.

94095 - Amoxicillin

The concentration of antimicrobial agents in body fluids, most notable serum or plasma, are used to regulate therapy to ensure effective dosing (especially with oral agents where GI absorption is in question), to monitor accumulation to help minimize toxicity, and to help evaluate the pharmacokinetics of new agents. Both peak and trough levels obtained immediately after dosing or immediately prior to new dosing, respectively, may be monitored.

3557 - Gabapentin

Gabapentin is an anticonvulsant drug commonly used as adjunctive therapy to treat partial seizures. Therapeutic drug monitoring is useful to optimize dose and to avoid toxicity.

94031 - Drug Monitoring, Antidepressants, with Confirmation, Serum

Antidepressants are medications that can be used to treat mild, moderate, and severe depression. These medications may also be used to treat anxiety and eating disorders as well as pain (fibromyalgia and neuropathic). Antidepressant drug testing is intended for use in prescription adherence monitoring of patients prescribed antidepressant medications. Adherence monitoring requires prescribed drugs to be present, and the absence of non-prescribed drugs for these patient populations. Drug testing for prescription adherence can provide information for improvement of patient care. The results of drug testing can often prompt important clinical discussions with patients.

30292 - Heparin, Anti-Xa

This assay is useful in measuring heparin concentration in patients treated with low molecular weight heparins (i.e. Enoxaparin/Lovenox) or unfractionated heparin. It is not intended for measurement of Rivaroxaban (Xarelto) or Fondaparinux (Arixtra).
Refer to test code 90981 for Rivaroxaban measurement and test code 16103 for Fondaparinux measurement.

888 - Tobramycin

Tobramycin is an aminoglycoside antibiotic used in the treatment of gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and also Staphylococcus. Tobramycin is potentially nephrotoxic and ototoxic and serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

916 - Valproic Acid

Valproic acid is used as an anticonvulsant to treat certain types of seizures, to prevent migraine headaches and to treat various psychiatric illnesses such as bipolar disorder and aggression. Drugs that compete for protein-binding sites with valproic acid can increase the concentration of valproic acid. Therapeutic drug monitoring is useful to optimize dose. Measurement of the free concentration is useful if toxicity is suspected.

36637 - Oxcarbazepine Metabolite

Oxcarbazepine (trileptal) is an anti-convulsant used for treating generalized tonic-clonic and partial seizures. It can be administered alone or as an adjunct to other anti-convulsants. Clinically significant effects of oxcarbazepine are observed when plasma levels of its active metabolite, 10-OH-carbazepine, are between 15 and 35 ug/mL. Toxic symptoms may occur when plasma levels exceed 35 ug/mL. The therapeutic monitoring of oxcarbazepine and its active metabolite are important for achieving proper serum/plasma concentration to inhibit epileptic seizures and avoid adverse effects. The precise mechanism of the action by which oxcarbazepine and its active metabolite exert their antiseizure effect is unknown. However, in vitro electro-physiological studies indicate that they produce blockade of voltage-sensitive sodium channels, resulting in the stabilization of hyperexcited neural membranes, inhibition of repetitive neuronal firing, and diminution of propagation of synaptic impulses. These are important in prevention of seizure spread in the brain. In addition, the increased potassium conduction and calcium channel activities may contribute to the antiseizure treatment effects. After oral administration, oxcarbazepine is readily absorbed in the body, followed by rapid and almost complete metabolization to 10-OH-carbazepine, active metabolite. The half-life of oxcarbazepine is only 1 to 2.5 hours, while that of 10-OH-carbazepine is 11 to 15 hours. The protein binding of oxcarbazepine is about 67%, whereas that of the metabolite is about 38%. The clearance of oxcarbazepine and its active metabolite from the body is mainly through ketone reduction and O-site conjugation with glucuronic acid rather than oxidative processes via cytochrome P450 system. More than 95% of the treatment dosage is excreted by the kidneys. Fecal excretion only accounts for less than 4%.

8575 - Gentamicin, Trough

Gentamicin is an aminoglycoside antibiotic used in the treatment of gram-positive and gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and Staphylococcus. Gentamicin is potentially nephrotoxic and ototoxic. Serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

70073 - Olanzapine

Therapeutic drug monitoring of antipsychotic drug.

94032 - Drug Monitoring, Antidepressants, with Confirmation, Urine

The monitoring of the parent compounds and metabolites in urine of the group of drugs classified as Antidepressants.

412 - Desipramine

Desipramine is a tricyclic antidepressant. Therapeutic drug levels are monitored to assist the physician assessing therapeutic response and to avoid toxicity.

16262 - Lacosamide

Lacosamide is an antiepileptic medication. Monitoring the serum concentration is beneficial to ensure compliance with drug therapy.

94529 - Drug Monitoring, Antipsychotics, with Confirmation, Serum

Antipsychotic (AP) drugs are widely prescribed for the treatment of schizophrenia and psychosis. The so-called first generation or typical APs were developed in the 1950s and show severe side-effects such as extrapyramidal symptoms due to their pharmacological action on d2 and d4 receptors. As a measure of reducing these severe side-effects, a range of ‘second generation’ APs were developed. These newer generation drugs act considerably less on d2 and d4 receptors and therefore exhibit less extrapyramidal side-effects.
Over the last decade, the prescription rate of APs (more notably second generation) has increased worldwide, [1-3] especially among young adults and children [1-4]. However, second generation APs are not entirely free of side-effects. Irrespective of their generation, it has been shown that these drugs can increase the risk of sudden cardiac death with studies showing that the risk of sudden cardiac death is increased threefold among patients treated with APs.

93744 - Perampanel, Serum/Plasma

Therapeutic drug monitoring.

3189 - Phenytoin, Free

Phenytoin is used singly or in combination with other anticonvulsants to treat grand mal epilepsy. Monitoring the serum levels of antiepileptic drugs has increased the efficiency and safety of drug therapy in epilepsy. It facilitates individualization of dosage regimen, reveals irregular drug intake and identifies the responsible agent in intoxicated patients on multiple drug therapy. Free phenytoin is especially useful in patients with altered phenytoin binding to protein, e.g., uremia or individuals having abnormally low levels of albumin, such as nephrotic syndrome. Free phenytoin in serum correlates better with the various other free compartments of the body than does the total drug and is probably a better estimate of the "active drug level" at the receptor site and agrees more with the clinical response.

7311 - Anticonvulsant Panel 1

See individual tests.

26513 - Carbamazepine and Metabolite, Total

Carbamazepine and its metabolite (10,11-carbamazepine epoxide) are widely used for control of generalized tonic-clonic, partial-onset, complex and mixed seizure disorders. The metabolism of carbamazepine in epileptic patients has several different pathways that can be altered when the patient is co-medicated with other anticonvulsants and, therefore, it's therapeutic level should be monitored along with its metabolite in their free and protein bound states.

30965 - Topiramate

Topiramate is an anticonvulsant used as an adjunctive treatment of partial-onset epilepsy. Therapeutic drug monitoring is useful to optimize dose and avoid toxicity.

4732 - Trazodone, Serum

For therapeutic drug monitoring of antidepressant therapy. Peak plasma levels occur approximately 1 hour after dosing when Trazodone is taken on an empty stomach or 2 hours after dosing when taken with food. Elimination of Trazodone is biphasic, consisting of an initial phase (half-life 3-6 hours) followed by a slower phase (half-life 5-9 hours).

8579 - Vancomycin, Trough

Vancomycin is an antibiotic used in the treatment of bacterial infections, especially methicillin-resistant staphylococci. Vancomycin is also used in treatment for penicillin-allergic patients who cannot receive or have failed to respond to other drugs, including the penicillins and/or cephalosporins and for other infections caused by vancomycin-susceptible organisms.

805 - Salicylate

Salicylates are used in the treatment of fever, analgesia and in the treatment of acute rheumatic fever, rheumatoid arthritis and for inhibition of platelet aggregation in patients with CAD. When treating rheumatoid arthritis, salicylates reduce the inflammation in joint tissues. Salicylate levels are monitored to assess toxicity.

16823 - Duloxetine, Serum/Plasma

Antidepressant.

8389 - Fluoxetine

Fluoxetine is an antidepressant drug that is also used in the treatment of bulimia nervosa and obsessive-compulsive disorder. Therapeutic drug monitoring is useful to optimize dose and to avoid toxicity.

91895 - Paliperidone

Paliperidone is an atypical antipsychotic drug. It is identical to 9-hydroxyrisperidone, the pharmacological active metabolite of Risperidone, and has a similar pharmacological profile as Risperidone. For treatment optimization, monitoring Paliperidone serum concentrations may be useful.

8592 - Bupropion and Metabolite, Serum/Plasma

Bupropion is an antidepressant for treating mental depression. Monitoring its level is important to optimize therapy, to avoid toxicity and to assure compliance.

743 - Procainamide

Procainamide is used to treat a variety of atrial and ventricular arrhythmias. Metabolism of procainamide produces an active metabolite N-Acetylprocainamide (NAPA). The concentration of both procainamide and NAPA levels are monitored to assure adequate therapeutic levels of procainamide are achieved and to avoid toxicity.

16103 - Fondaparinux Sodium (Xa Inhibition)

Fondaparinux sodium (Arixtra) is a factor Xa inhibitor indicated for the prophylaxis and treatment of deep venous thrombosis and pulmonary embolism in certain patient populations. The antithrombotic activity of Arixtra is the result of antithrombin III-mediated selective inhibition of Factor Xa. Neutralization of factor Xa interrupts thrombin formation and thrombus development. The anti-Factor Xa activity of the drug can be measured using the chromogenic anti-Xa method using Arixtra as the calibrator.

613 - Lithium

Lithium is used to treat manic-depressive disorders and the manic phase of affective disorders, including mania. The therapeutic window is relatively small. Therapeutic drug monitoring is useful to optimize dose and avoid toxicity.

8812 - Cyclosporine A Trough, Blood

Cyclosporine (Cyclosporin A) is an immunosuppressant therapeutic agent used in the prevention of organ graft rejection. Measurement of blood levels is recommended due to the inter-individual variability of metabolism as well as the toxicity associated with excessive dosage.

30348 - Mirtazapine, Serum/Plasma

Therapeutic drug monitoring.

5374 - Bismuth, Blood

Excessive use of bismuth containing medications may cause renal damage and other adverse effects.

36676 - Carbamazepine-10,11-Epoxide, Serum/Plasma

Carbamazepine and its metabolite (10,11-Carbamazepine epoxide) are widely used for control of generalized tonic-clonic, partial-onset, complex and mixed seizure disorders. The metabolism of carbamazepine in epileptic patients has several different pathways that can be altered when the patient is co-medicated with other anticonvulsants and, therefore, its therapeutic level should be monitored along with its metabolite in their free and protein bound states.

16296 - Rufinamide

Rufinamide is an antiepileptic indicated for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in children and adults. As multiple antiepileptics may be administered, it may be important to (1) optimize therapy, (2) monitor compliance, and (3) avoid toxicity.

10662 - Mycophenolic Acid, LC/MS/MS

Mycophenolic acid is an immunosuppressant used in tissue transplants. It prevents graft rejection by the host's immune system. It is very important to monitor its level. Too little of this drug will cause graft rejection, while too much will lead to infection. Monitoring its level is essential to optimize therapeutic effects, avoid toxicity, and assure compliance.

15922 - Aripiprazole, Quantitative, Serum/Plasma

Aripiprazole (Abilify®) is an atypical antipsychotic and antidepressant used in the treatment of schizophrenia, bipolar disorder, and clinical depression. The analysis of aripiprazole is used to monitor compliance with drug therapy.

18885 - Oxycodone and Metabolite, Quantitative

For therapeutic drug monitoring of oxycodone (Oxycontin®, Percocet®, Percodan®). Oxycodone is a semisynthetic opioid analgesic. Steady state concentration is reached in 24-36 hours after initiation of therapy. Elimination half-life of oxycodone is 4.5 hours for controlled release and 3.2 hours for immediate release formulations. Peak plasma concentration of oxycodone is 11, 21, 39, 99, or 156 ng/mL after a single oral dose of 10, 20, 40, 80, or 160 mg respectively. Oxymorphone is a minor but active metabolite of oxycodone that is present at lower concentration in the circulation. Therapeutic concentrations for oxymorphone have not been established.

70071 - Benzodiazepines, Serum

Benzodiazepines are widely used as anxiolytics, sedative- hypnotics, muscle relaxants, and anticonvulsants. Benzodiazepines include drugs such as diazepam Valium®, chlordiazepoxide Librium®, oxazepam Serax®, lorazepam Ativan®, alprazolam Xanax®, clonazepam Clonopin® and triazolam Halcion®. Many common benzodiazepines are detected in urine by their metabolites oxazepam and nordiazepam. Psychological and physiological addictions, misuse and abuse of benzodiazepines have been described.

5406 - Vancomycin, Peak and Trough

Vancomycin is an antibiotic used in the treatment of bacterial infections, especially methicillin-resistant staphylococci. Vancomycin is also used in treatment for penicillin-allergic patients who cannot receive or have failed to respond to other drugs, including the penicillins and/or cephalosporins and for other infections caused by vancomycin-susceptible organisms.

18865 - Leflunomide Metabolite

Leflunomide is an immunosuppressant medication used in the treatment of rheumatoid arthritis. Leflunomide is rapidly and extensively metabolized to teriflunomide, which is the active form of the medication. Steady state plasma concentrations in patients receiving recommended daily dosages: up to 63,000 ng/mL. It is recommended that all women of childbearing potential who discontinue leflunomide and women receiving treatment who wish to become pregnant undergo the cholestyramine drug elimination procedure. This procedure includes verification that plasma levels of teriflunomide are less than 20 ng/mL by two separate tests at least 14 days apart.

36330 - Levetiracetam, Immunoassay

LEV is currently used as an anti-epileptic drug for the treatment of adult partial seizures particularly as an add-on therapy for refractory patients. It also has potential for other anxiety and cognitive disturbances.

890 - Tobramycin, Peak and Trough

Tobramycin is an aminoglycoside antibiotic used in the treatment of gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and also Staphylococcus. Tobramycin is potentially nephrotoxic and ototoxic and serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

18866 - Pregabalin

Pregabalin is an anti-epileptic drug. It works by slowing down impulses in the brain that cause seizures. Pregabalin also affects chemicals in the brain that send signals across the nervous system. Pregabalin is used to control seizures and to treat fibromyalgia.

91123 - Chlordiazepoxide and Metabolites

This definitive drug assay is used to measure concentrations of chlordiazepoxide, norchlordiazepoxide, and nordiazepam in serum. This therapeutic drug monitoring assay may be used to assess if chlordiazepoxide and metabolites are within therapeutic range. Urine and oral fluid are the specimens of choice for routine monitoring of patients taking prescription drugs.

Chlordiazepoxide is a long-acting benzodiazepine used to treat adults for anxiety disorder, preoperative apprehension and anxiety, and withdrawal symptoms of acute alcohol use disorder. It is also used to treat children older than 6 years for anxiety.

Chlordiazepoxide has several active metabolites, and prolonged duration of action may lead to serious adverse effects in older individuals, children, and individuals with disabilities or hepatic or renal impairment. Common adverse effects include drowsiness, fatigue, dizziness, ataxia, forgetfulness, slurred speech, irritability, and rash. Chlordiazepoxide intoxication and overdose can be life-threatening, especially when chlordiazepoxide is combined with alcohol and other central nervous system depressants [1,2]. However, routine quantitative tests of chlordiazepoxide are not needed unless medical conditions warrant monitoring or for individuals taking other drugs that increase the risk of intoxication [2].

The results of this test should be interpreted in the context of pertinent clinical history and physical examination findings.

References
1. Chlordiazepoxide. In: Fuller MA, et al, eds. Drug Information Handbook for Psychiatry. 7th ed. Lexi-Comp Inc; 2009:316-319.
2. Whyte IM. Benzodiazepines. In: Dart RC, et al. Medical Toxicology. 3rd ed. Lippincott Williams & Wilkins; 2004:811-823.

90981 - Rivaroxaban

Rivaroxaban is an oral factor Xa inhibitor that is indicated to reduce the risk of stroke and systemic embolism in patients with nonvalvular atrial fibrillation. It is also indicated for the treatment, prophylaxis, or the reduction in the risk of reoccurrence of deep vein thrombosis (DVT) or pulmonary embolism (PE). Rivaroxaban does not need to be monitored routinely, however, exceptions may include determination of failure of therapy vs. poor compliance, or potential dose adjustment required for renal or hepatic dysfunction.

93031 - Buprenorphine and Metabolites, LC/MS/MS, Serum

The analysis of buprenorphine and metabolites is useful for the monitoring of compliance to drug therapy.

713 - Phenytoin

Phenytoin is an anticonvulsant hydantoin used for the treatment of generalized tonic-clonic (grand mal) and complex partial seizures. Phenytoin is also used for prophylaxis in neurosurgical procedures. Phenytoin levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.

826 - Doxepin

Doxepin is a tricyclic antidepressant. Therapeutic drug levels are monitored to assist the physician assessing therapeutic response and to avoid toxicity.

Sirolimus (Rapamycin)

This test is used to monitor immunosuppressive therapy following organ transplant.
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