EQUETRO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for EQUETRO (EQUETRO).
Equetro (carbamazepine extended-release) is an anticonvulsant and mood stabilizer. It stabilizes the inactivated state of voltage-gated sodium channels, thereby inhibiting repetitive neuronal firing and reducing synaptic transmission. It also potentiates GABA receptors and inhibits glutamate release.
| Metabolism | Primarily hepatic via CYP3A4 to carbamazepine-10,11-epoxide (active metabolite); also metabolized by CYP2C8 and UGT2B7. Autoinduction of its own metabolism occurs. |
| Excretion | Renal: 2% excreted unchanged (carbamazepine) in urine; 15% as carbamazepine-10,11-epoxide; 30% as other metabolites; biliary/fecal: 50-60% as metabolites. |
| Half-life | Carbamazepine: 25-65 hours (initial single dose), 12-17 hours (chronic dosing due to autoinduction); carbamazepine-10,11-epoxide: 5-8 hours. |
| Protein binding | 75-90% bound to albumin and alpha1-acid glycoprotein (carbamazepine); 50% bound (epoxide metabolite). |
| Volume of Distribution | 0.8-2.0 L/kg (total carbamazepine); higher in neonates and children; reflects extensive tissue distribution and CNS penetration. |
| Bioavailability | Extended-release oral: 75-85% compared to immediate-release (due to slower absorption and reduced first-pass metabolism). |
| Onset of Action | Extended-release oral: 4-8 hours for initial effect; therapeutic steady state achieved in 2-4 weeks. |
| Duration of Action | Extended-release oral: 12-24 hours per dose (maintenance of therapeutic levels); clinical effect sustained with twice-daily dosing. |
Initial: 50 mg orally twice daily; increase by 50-100 mg/day every 2-4 weeks. Usual maintenance: 100-200 mg orally twice daily. Maximum: 200 mg orally twice daily.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | GFR 30-89 mL/min: No adjustment required. GFR 15-29 mL/min: Reduce dose by 50%. GFR <15 mL/min: Use with caution; reduce dose by 75% or consider alternative. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 50%. Child-Pugh Class C: Use with caution; reduce dose by 75% and monitor closely. |
| Pediatric use | Not approved for patients <18 years. Safety and efficacy not established. |
| Geriatric use | Start at low end of dosing range (50 mg twice daily), titrate slowly due to increased risk of renal impairment and drug accumulation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for EQUETRO (EQUETRO).
| Breastfeeding | Carbamazepine is excreted into breast milk with an M/P ratio of approximately 0.4-0.6. Relative infant dose is about 2-5% of maternal weight-adjusted dose. Adverse effects include drowsiness, poor suckling, and hepatic enzyme induction. Breastfeeding is generally considered acceptable with infant monitoring for sedation and weight gain. The American Academy of Pediatrics considers carbamazepine compatible with breastfeeding. |
| Teratogenic Risk | EQUETRO (carbamazepine) is classified as FDA Pregnancy Category D. First trimester exposure increases risk of neural tube defects (e.g., spina bifida) approximately 1-2% above baseline. Craniofacial defects, fingernail hypoplasia, and developmental delay are associated. Second and third trimester exposure may cause neonatal withdrawal, vitamin K deficiency (hemorrhagic disease), and transient hepatic dysfunction. Antiepileptic Drug Pregnancy Registry data confirm increased major congenital malformations. |
■ FDA Black Box Warning
Serious dermatologic reactions including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), particularly in patients with the HLA-B*1502 allele. Aplastic anemia and agranulocytosis may occur; obtain baseline CBC and monitor frequently.
| Serious Effects |
History of bone marrow depression, hypersensitivity to carbamazepine or tricyclic antidepressants, MAOI use within 14 days, concurrent use of nefazodone, and known HLA-B*1502 allele (unless benefit outweighs risk).
| Precautions | Hematologic toxicity (monitor CBC), dermatologic reactions (SJS/TEN), hypersensitivity syndrome, exacerbation of seizures (if not titrated slowly), hyponatremia (SIADH), hepatic effects, glaucoma (increases intraocular pressure), and cognitive impairment. |
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| Fetal Monitoring | Monitor serum carbamazepine levels (therapeutic range 4-12 mcg/mL) every 4-8 weeks during pregnancy due to increased clearance. Fetal ultrasound at 18-20 weeks for neural tube defects. Assess maternal folate levels; supplement with 4-5 mg/day folic acid preconception and throughout first trimester. Monitor maternal liver function tests, CBC with platelets, and thyroid function. Neonatal monitoring for withdrawal symptoms, coagulation (administer vitamin K immediately after birth), and hepatic function. |
| Fertility Effects | Carbamazepine may induce hepatic cytochrome P450 enzymes, increasing clearance of sex steroids. This can reduce efficacy of hormonal contraceptives and potentially cause menstrual irregularities (anovulation, oligomenorrhea) through altered estrogen/progesterone metabolism. While not directly impairing fertility, these effects may complicate conception timing. In men, carbamazepine has been associated with decreased sperm count and motility, though reversibility is likely upon discontinuation. |