Davis's Lab & Diagnostic Tests

Anticonvulsant Drugs: Carbamazepine, Ethosuximide, Lamotrigine, Phenobarbital, Phenytoin, Primidone, Valproic Acid

Anticonvulsant Drugs: Carbamazepine, Ethosuximide, Lamotrigine, Phenobarbital, Phenytoin, Primidone, Valproic Acid is a topic covered in the Davis's Lab & Diagnostic Tests.

To view the entire topic, please or purchase a subscription.

Davis’s Laboratory and Diagnostic Tests Online, powered by Unbound Medicine, provides nurses and students access to 400+ test monographs containing reference ranges, indications, patient preparation and result interpretation. Explore these free sample topics:


-- The first section of this topic is shown below --


Carbamazepine (Carbamazepinum, Carbategretal, Carbatrol, Carbazep, CBZ, Epitol, Tegretol, Tegretol XR); ethosuximide (Suxinutin, Zarontin, Zartalin); lamotrigine (Lamictal) phenobarbital (Barbital, Comizial, Fenilcal, Gardenal, Phenemal, Phenemalum, Phenobarb, Phenobarbitone, Phenylethylmalonylurea, Solfoton, Stental Extentabs); phenytoin (Antisacer, Dilantin, Dintoina, Diphenylan Sodium, Diphenylhydantoin, Ditan, Epanutin, Epinat, Fenitoina, Fenytoin, Fosphenytoin); primidone (Desoxyphenobarbital, Hexamidinum, Majsolin, Mylepsin, Mysoline, Primaclone, Prysolin); valproic acid (Depacon, Depakote, Depakote XR, Depamide, Dipropylacetic Acid, Divalproex Sodium, Epilim, Ergenyl, Leptilan, 2–Propylpentanoic Acid, 2–Propylvaleric Acid, Valkote, Valproate Semisodium, Valproate Sodium)

Common Use:
To monitor specific drugs for subtherapeutic, therapeutic, or toxic levels in evaluation of treatment.

Serum collected in a red-top tube.

Drug*Route of Administration
Phenytoin Oral
Valproic acidOral
*Recommended collection time = trough: immediately before next dose (at steady state) or at a consistent sampling time.

Normal Findings:
(Method: Immunoassay for all except lamotrigine; liquid chromatography/tandem mass spectrometry for lamotrigine)

DrugTherapeutic Range Conventional UnitsConversion to SI UnitsTherapeutic Range SI UnitsHalf-Life (hr)Volume of Distribution (L/kg)Protein Binding (%)Excretion
Carbamazepine4–12 mcg/mLSI units = Conventional units × 4.2317–51 micromol/L15–400.8–1.860–80Hepatic
Ethosuximide40–100 mcg/mLSI units = Conventional units × 7.08283–708 micromol/L25–700.70–5Renal
Lamotrigine1–14 mcg/mLSI units = Conventional units × 3.94–55 micromol/L25–330.9–1.350–5Hepatic
PhenobarbitalAdult: 15–40 mcg/mLSI units = Conventional units × 4.31Adult: 65–172 micromol/LAdult: 50–1400.5–140–5080% hepatic and 20% renal
Child: 15–30 mcg/mLSI units = Conventional units × 4.31Child: 65–129 micromol/LChild: 40–7080% hepatic and 20% renal
Phenytoin 10–20 mcg/mLSI units = Conventional units × 3.9640–79 micromol/L20–400.6–0.785–95Hepatic
PrimidoneAdult: 5–12 mcg/mLSI units = Conventional units × 4.58Adult: 23–55 micromol/L4–120.5–10–20Hepatic
Child: 7–10 mcg/mLSI units = Conventional units × 4.58Child: 32–46 micromol/L
Valproic acid50–125 mcg/mLSI units = Conventional units × 6.93347–866 micromol/L8–150.1–0.585–95Hepatic

-- To view the remaining sections of this topic, please or purchase a subscription --