EPITOL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for EPITOL (EPITOL).
Carbamazepine stabilizes the inactivated state of voltage-gated sodium channels, thereby inhibiting high-frequency repetitive firing of action potentials and reducing synaptic transmission.
| Metabolism | Primarily metabolized by CYP3A4 to carbamazepine-10,11-epoxide (active metabolite), which is further metabolized by epoxide hydrolase. Also induces its own metabolism via CYP3A4 induction. |
| Excretion | Renal: 70% (as glucuronide conjugates and other metabolites), Fecal: 30% (unchanged and metabolites) |
| Half-life | 20-40 hours (mean 30 hours); linear kinetics at therapeutic doses; decreased with concomitant enzyme-inducing drugs |
| Protein binding | 90-95% (primarily to albumin); saturable at high concentrations |
| Volume of Distribution | 0.5-0.8 L/kg (central compartment 0.2-0.3 L/kg); reflects extensive tissue distribution, especially in brain and liver |
| Bioavailability | Oral: 85-95% (immediate-release); 70-85% (extended-release due to incomplete absorption); IV: 100% |
| Onset of Action | Oral: 4-12 hours (time to steady-state therapeutic concentration); IV (fosphenytoin): 0.5-1 hour for peak effect |
| Duration of Action | 24 hours (once-daily dosing); extended-release formulations provide sustained levels over 24 hours |
Carbamazepine, immediate-release: initial 200 mg orally twice daily; increase by 200 mg/day at weekly intervals. Typical maintenance: 800-1200 mg/day in 2-3 divided doses. Extended-release: initial 200 mg orally twice daily; maintenance 400-600 mg twice daily.
| Dosage form | TABLET, CHEWABLE |
| Renal impairment | No specific dosage adjustment recommended based on GFR. Use with caution in severe renal impairment (CrCl <10 mL/min). |
| Liver impairment | Contraindicated in acute hepatic porphyria. For Child-Pugh A (mild): reduce initial dose and titrate slowly. Child-Pugh B or C: contraindicated or use with extreme caution; significant dose reduction recommended, but no specific guidelines available. |
| Pediatric use | For epilepsy: children >6 years, initial 10-20 mg/kg/day orally divided twice or thrice; increase weekly by 100 mg/day. Maintenance: 10-20 mg/kg/day (max 1000 mg/day for 6-12 years; 1200 mg/day for >12 years). |
| Geriatric use | Start at lower end of dosing range (100-200 mg orally twice daily) due to increased sensitivity, slower clearance, and higher risk of hyponatremia and sedation. Monitor serum levels and renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for EPITOL (EPITOL).
| Breastfeeding | Carbamazepine is excreted into breast milk with a milk-to-plasma (M/P) ratio of approximately 0.2–0.4. Infant serum levels are low (usually <3 mg/L). American Academy of Pediatrics considers it compatible with breastfeeding. Monitor infant for drowsiness, poor feeding, and rash. Benefit of breastfeeding outweighs low risk in most cases. |
| Teratogenic Risk | EPITOL (carbamazepine) is classified as FDA Pregnancy Category D. First trimester exposure increases risk of neural tube defects (spina bifida, anencephaly), craniofacial anomalies, and developmental delay. Risk is dose-dependent; monotherapy at lowest effective dose reduces risk. Second and third trimester exposure may cause fetal anticonvulsant syndrome, intrauterine growth restriction, and neonatal hemorrhage due to vitamin K deficiency. Carbamazepine crosses placenta; fetal serum levels approximate maternal levels. |
■ FDA Black Box Warning
Aplastic anemia and agranulocytosis have been reported in association with carbamazepine therapy. Patients should be informed of the early signs and symptoms of potential hematologic issues, such as fever, sore throat, mouth ulcers, easy bruising, petechial or purpuric hemorrhage. Obtain complete pretreatment hematologic testing as a baseline. If any evidence of bone marrow depression develops, the drug should be discontinued.
| Serious Effects |
["History of bone marrow depression","Hypersensitivity to carbamazepine or tricyclic antidepressants (cross-sensitivity)","Use of MAO inhibitors within 14 days","History of porphyria","AV heart block"]
| Precautions | ["Hypersensitivity reactions including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) - screen for HLA-B*1502 allele in Asian populations","Serious dermatologic reactions","Aplastic anemia and agranulocytosis","Suicidal behavior and ideation","Hyponatremia (SIADH)","Dizziness and drowsiness","Hepatic effects (elevated liver enzymes, hepatitis)","Drug interactions (CYP3A4 induction reduces efficacy of oral contraceptives, warfarin, etc.)","Abrupt discontinuation may precipitate seizures"] |
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| Fetal Monitoring | Monitor maternal serum carbamazepine levels monthly; target trough 4–12 mg/L. Assess liver function, complete blood count, electrolytes, and renal function every trimester. Fetal ultrasound at 16–20 weeks for neural tube defects; consider amniocentesis for alpha-fetoprotein if indicated. Nonstress test and biophysical profile in third trimester if growth restriction. Vitamin K 10 mg/day orally from 36 weeks to prevent neonatal hemorrhage. |
| Fertility Effects | Carbamazepine may induce hepatic cytochrome P450 enzymes, accelerating metabolism of oral contraceptives, potentially reducing efficacy. Enzyme induction can also affect endogenous hormone levels, but no direct impairment of fertility. No evidence of decreased spermatogenesis or ovulatory dysfunction in humans. |