Can carbamazepine and oxcarbazepine (anticonvulsants) be administered together?

From the Guidelines

Carbamazepine and oxcarbazepine can be given, but not necessarily together, as they are both effective in treating paroxysmal kinesigenic dyskinesia (PKD) with over 85% of patients achieving complete remission with low-dose therapy 1. When considering the use of these medications, it's essential to understand their efficacy and potential side effects.

• The recommended initial dosage of carbamazepine is 50 mg, which can be adjusted according to the practical effect 1.
• For oxcarbazepine, the initial recommended dosage is 75 mg 1.
• It's crucial to note that the dosage should be flexible, as the extent of satisfaction with the treatment is subjective and individualized 1.
• Additionally, patients should be screened for HLA-B*15:02 before initiating carbamazepine treatment to reduce the risk of adverse cutaneous reactions, particularly in the Han Chinese population 1.
• If a patient cannot tolerate carbamazepine or has a certain genetic marker, other voltage-gated sodium channel blockers like lamotrigine, topiramate, and phenytoin sodium can be considered as second-line treatment 1.
• The decision to use either carbamazepine or oxcarbazepine should be based on the individual patient's needs and response to treatment, rather than combining them, which may increase the risk of adverse effects without providing significant additional therapeutic benefits 1.

From the FDA Drug Label

7.2 Effect of Other Drugs on Oxcarbazepine Strong inducers of cytochrome P450 enzymes and/or inducers of UGT (e.g., rifampin, carbamazepine, phenytoin and phenobarbital) have been shown to decrease the plasma/serum levels of MHD, the active metabolite of oxcarbazepine (25% to 49%) [see Clinical Pharmacology (12.3)]. Combination Therapy:Carbamazepine may be used alone or with other anticonvulsants When added to existing anticonvulsant therapy, the drug should be added gradually while the other anticonvulsants are maintained or gradually decreased, except phenytoin, which may have to be increased

• Concomitant use: Carbamazepine and oxcarbazepine can be given together, but with caution.
• Dose adjustment: The dose of oxcarbazepine may need to be adjusted when given with carbamazepine, as carbamazepine can decrease the plasma levels of the active metabolite of oxcarbazepine.
• Monitoring: Plasma levels of the active metabolite of oxcarbazepine should be monitored when given with carbamazepine. 2

From the Research

Comparison of Carbamazepine and Oxcarbazepine

• Oxcarbazepine is a 10-keto analogue of carbamazepine, but has a distinct pharmacokinetic profile 3
• The mechanism of action of oxcarbazepine involves mainly blockade of sodium currents, but differs from carbamazepine by modulating different types of calcium channels 4, 5
• Oxcarbazepine undergoes reductive metabolism, whereas carbamazepine is oxidized by the cytochrome P-450 system 4, 5

Efficacy and Tolerability

• Oxcarbazepine is as effective as carbamazepine in reducing seizure frequency in patients with partial epilepsy 6, 3
• Oxcarbazepine is better tolerated than carbamazepine, with fewer rashes and less impact on thyroid and sexual hormone abnormalities 5
• Oxcarbazepine has a lower propensity for interactions with other drugs compared to carbamazepine 6

Clinical Use

• Oxcarbazepine can be used as monotherapy or adjunctive therapy for the treatment of partial seizures with or without secondary generalization in adults and children 4, 5
• The recommended titration scheme for oxcarbazepine in adults is to start with 150 mg/day at night and increase by 150 mg/day every second day until a target dose of 900-1200 mg/day is reached 7
• Oxcarbazepine may be a useful alternative to carbamazepine in the management of trigeminal neuralgia and affective disorders, but more research is needed to establish its efficacy in these areas 3