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 |
| Molecular Weight | 252.27 |
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 | Associated with increased risk of major congenital malformations (e.g., neural tube defects, cleft palate) when used during the first trimester; use only if benefit outweighs risk. |
| 2nd trimester | Risk of fetal harm continues; lowest effective dose recommended. Monitor for maternal adverse effects. |
| 3rd trimester | May cause neonatal bleeding due to vitamin K deficiency; administer vitamin K to newborn. Withdrawal symptoms possible. |
Clinical note
Comprehensive clinical and safety monograph for EPITOL (EPITOL).
| Placental transfer | Extensive placental transfer; fetal serum levels may approach maternal levels. |
| Breastfeeding | Epitol passes into breast milk in low concentrations. Use with caution; monitor infant for drowsiness, rash, or liver function abnormalities. Generally considered compatible with breastfeeding if infant is healthy and not jaundiced. |
■ 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 |
Hypersensitivity to carbamazepine or any component of the formulationHistory of bone marrow suppressionConcomitant use with nefazodoneAcute intermittent porphyriaConcomitant use with colchicine in patients with renal or hepatic impairmentConcomitant use with delavirdineConcomitant use with non-nucleoside reverse transcriptase inhibitors
| 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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| Lactation Rating | L3 (Moderately Safe) |
| 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. |
| 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. |
| Food/Dietary | Grapefruit and grapefruit juice may mildly increase carbamazepine levels; avoid large amounts. Alcohol can exacerbate CNS depression; limit or avoid. High-fat meals may slightly decrease absorption; maintain consistent timing relative to meals. |
| Clinical Pearls | EPITOL (carbamazepine) requires slow titration to minimize CNS side effects; monitor for Stevens-Johnson syndrome, especially in HLA-B*1502-positive patients. Baseline CBC, LFTs, and serum electrolytes (sodium) recommended due to risk of hyponatremia. Induction of CYP3A4 may reduce efficacy of oral contraceptives, warfarin, and other co-administered drugs. |
| Patient Advice | Take with or without food, but be consistent with meals to avoid GI upset. · Do not crush or chew controlled-release tablets; swallow whole. · Stop drug and seek immediate medical attention if rash, blisters, or mouth sores develop. · Report any signs of infection, easy bruising, or bleeding (bone marrow suppression). · Use barrier contraception; carbamazepine reduces hormonal contraceptive effectiveness. · Do not abruptly discontinue; taper under medical supervision to prevent withdrawal seizures. |