General
Synonym/Acronym:
Carbamazepine (Carbamazepinum, Carbategretal, Carbatrol, Carbazep, CBZ, Epitol, Tegretol, Tegretol XR); ethosuximide (Suxinutin, Zarontin, Zartalin); lamotrigine (Lamictal) phenobarbital (Barbita, 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, Depakene, 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.
Specimen:
Serum (1 mL) collected in a red-top tube.
| Drug* | Route of Administration |
|---|
| Carbamazepine | Oral |
| Ethosuximide | Oral |
| Lamotrigine | Oral |
| Phenobarbital | Oral |
| Phenytoin | Oral |
| Primidone | Oral |
| Valproic Acid | Oral |
| *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)
| Drug | Therapeutic Range* | SI Units | Half-Life (hr) | Volume of Distribution (L/kg) | Protein Binding (%) | Excretion |
| (SI = Conventional Units × 4.23) |
| Carbamazepine | 4–12 mcg/mL | 17–51 micromol/L | 15–40 | 0.8–1.8 | 60–80 | Hepatic |
| (SI = Conventional Units × 7.08) |
| Ethosuximide | 40–100 mcg/mL | 283–708 micromol/L | 25–70 | 0.7 | 0–5 | Renal |
| (SI = Conventional Units × 3.905) |
| Lamotrigine | 1–4 mcg/mL** | 4–16 micromol/L | 25–33 | 0.9–1.3 | 50–5 | Hepatic |
| (SI = Conventional Units × 4.31) |
| Phenobarbital | Adult: 15–40 mcg/mL | Adult: 65–172 micromol/L | Adult: 50–140 | 0.5–1 | 40–50 | 80% Hepatic |
| Child: 15–30 mcg/mL | Child: 65–129 micromol/L | Child: 40–70 | | | 20% Renal |
| (SI = Conventional Units × 3.96) |
| Phenytoin | 10–20 mcg/mL | 40–79 micromol/L | 20–40 | 0.6–0.7 | 85–95 | Hepatic |
| (SI = Conventional Units × 4.58) |
| Primidone | Adult: 5–12 mcg/mL | Adult: 23–55 micromol/L | 4–12 | 0.5–1 | 0–20 | Hepatic |
| Child: 7–10 mcg/mL | Child: 32–46 micromol/L | | | | |
| (SI = Conventional Units × 6.93) |
| Valproic acid | 50–125 mcg/mL | 347–866 micromol/L | 8–15 | 0.1–0.5 | 85–95 | Hepatic |
| *Conventional units. |
Anticonvulsant Drugs: Carbamazepine, Ethosuximide, Lamotrigine, Phenobarbital, Phenytoin, Primidone, Valproic Acid has been found in Davis's Lab & Diagnostic Tests
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