Single-dose pharmacokinetics of felbamate in patients with renal dysfunction

The purpose of this study was to evaluate the effects of renal impairment on the single-dose pharmacokinetics of the antiepileptic felbamate.

Twelve subjects with three levels of renal dysfunction (creatinine clearance > 30-80, > 10-30 or 5-10 m min(-1)) and four controls with normal renal function (creatinine clearance > 80 ml min(-1) were studied). Plasma and urine samples were obtained for 144 h following administration of a single 1200 mg dose.

Compared with controls, apparent total body clearance, renal clearance and urinary excretion of felbamate were decreased, and half-life, Cmax and AUC values were increased in subjects with renal dysfunction. The magnitude of these changes was associated with the degree of renal dysfunction. Nonrenal clearance and apparent volume of distribution values were also lower in renal dysfunction subjects, but there was no association between the extent of these changes and degree of renal dysfunction. Renal clearance of felbamate accounted for approximately 30% of apparent total body clearance in the control group and from 9-22% in the renal failure patients. Renal clearance of felbamate was significantly correlated with creatinine clearance (r = 0.75; P< 0.001).

These data suggest that initial dosage and titration of felbamate may require adjustment in patients with renal dysfunction.