Oxcarbazepine is a second-generation antiepileptic drug (AED) and a keto-analogue of carbamazepine. It is a prodrug primarily metabolized to its active metabolite, 10-monohydroxy derivative (MHD). It is widely used in the Indian market for the management of partial seizures with or without secondary generalization in adults and children. It offers a favorable side effect profile and fewer drug interactions compared to carbamazepine.
Adult: **Initiation (Adjunctive Therapy):** 600 mg/day in two divided doses (300 mg BID). May be increased by 600 mg/day at weekly intervals. Recommended dose range: 600-2400 mg/day. **Initiation (Monotherapy):** 600 mg/day in two divided doses, increased by 300 mg/day every third day to a dose of 1200 mg/day. Further titration based on response.
Note: May be taken with or without food. Tablets should be swallowed whole with water. Do not crush or chew. The total daily dose should be administered in two equally divided doses (BID) to minimize peak-dose side effects.
The primary mechanism of action is blockade of voltage-sensitive sodium channels, leading to stabilization of hyperexcited neuronal membranes, inhibition of repetitive neuronal firing, and diminution of propagation of synaptic impulses.
Pregnancy: **Pregnancy Category C (US FDA).** Data suggests a 2-3 times increased risk of major congenital malformations (e.g., neural tube defects, cardiovascular) compared to the general population. Folate supplementation (5 mg/day) is recommended before and during pregnancy. Monotherapy at the lowest effective dose is preferred. Do not discontinue abruptly due to risk of status epilepticus. Indian guidelines recommend careful risk-benefit assessment and patient counseling.
Driving: May cause dizziness, drowsiness, diplopia, and ataxia, impairing the ability to drive or operate machinery. Patients should not drive until their individual response is known.
| Phenytoin | Oxcarbazepine decreases phenytoin levels by ~30-40%. Phenytoin decreases MHD levels by ~30%. | Major |
| Carbamazepine | Decreases MHD levels by ~30-40%. | Major |
| Valproic Acid | May decrease MHD levels slightly. Oxcarbazepine may decrease valproate levels. | Moderate |
| Phenobarbital | Decreases MHD levels by ~25%. | Moderate |
| Oral Contraceptives (Ethinyl Estradiol, Levonorgestrel) | Oxcarbazepine induces CYP3A4, reducing contraceptive hormone levels by up to 50%, increasing risk of contraceptive failure. | Major |
| Warfarin | May decrease warfarin efficacy via enzyme induction. Monitor INR closely. | Major |
| Felodipine | Oxcarbazepine may decrease felodipine levels, reducing antihypertensive effect. | Moderate |
| Verapamil | Verapamil may decrease MHD levels. | Moderate |
| Lithium | Increased risk of neurotoxicity (ataxia, tremor, nystagmus). | Moderate |