Synonyms: OCBZ, TOLEP, 10-OH carbazepine
Clinical significance
Oxcarbazepine is an anticonvulsant effective in partial epilepsy. It is a prodrug similar to carbamazepine (with a ketone group at position 10) with a similar mechanism of action (reducing nerve cell excitability by prolonging the inactivation of voltage-dependent sodium channels), but with fewer side effects and easier to manage. It is well absorbed from the gut and is rapidly reduced to the monohydroxy derivative 10-OH-CBZ (MHD), which in turn is eliminated by glucuronidation in the liver. The monohydroxy form (MHD) is the pharmacologically active metabolite responsible for the anticonvulsant activity. Its toxic effects involve the central nervous system (dizziness, ataxia, headache) and electrolyte balance (low sodium).
Clinical indications
Monitoring of treatment
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing or sitting upright for at least 30 minutes. For periodic monitoring of the blood concentration of the medicine, so that results can be compared over time, the blood sample should always be taken the same number of hours after taking the medicine.
Notes
Phenobarbital and phenytoin reduce its concentration. Blood sodium levels must be monitored constantly, as they can fall considerably, with serious effects on the body. When taken by mouth, bowel disturbances (diarrhoea) can reduce absorption of the medicine and therefore its blood concentration.
Monitoring oxcarbazepine in the blood, measured through its active metabolite (its monohydroxy derivative is detected in the chromatogram), is useful in combination therapy for epilepsy and in adjusting the dose.