After oral administration, oxcarbazepine is rapidly converted to its active monohydroxylated derivative (MHD), which provides most of its antiepileptic activity. Approximately 25% of MHD is cleared via the kidney.58 There is a linear correlation between decreased creatinine clearance and decreased MHD clearance.58 For patients with creatinine clearance values less than 30 mL/min, oxcarbazepine should be initiated at one-half the usual starting dose (300 mg/d). The dose then should be increased to achieve the desired clinical response.58
There are no clinical studies of the effects of hemodialysis on MHD plasma concentration.49 Oxcarbazepine is poorly soluble in water, has 40% protein binding, and a low volume of distribution. Given this profile, it is difficult to predict the extent of drug removal by hemodialysis. Plasma concentration determinations of MHD usually are not readily available for dosage adjustments after dialysis. Patients on hemodialysis who are taking oxcarbazepine should be followed closely.
Reviewed and revised February 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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