The effect of the artificial kidney on the removal of carbamazepine was studied in four uremic patients undergoing chronic hemodialysis. Each patient received 500 mg of carbamazepine PO 8 hr prior to hemodialysis. Predialysis and postdialysis blood samples as well as dialysate samples were collected at various time intervals during a 4-hr hemodialysis. Samples were analyzed for carbamazepine content by HPLC. Dialysis clearance calculated from dialysate measurements averaged 53.6 +/- 10.0 mL/min which is double the reported mean plasma clearance of 27.5 mL/min. Since drug clearance by the dialyzer is twice the endogenous plasma clearance, we conclude that carbamazepine is dialyzable. Despite the significant dialysis clearance, a dosage regimen adjustment may not be necessary because of the long elimination half-life of carbamazepine of 35 hr compared to the short length of the usual hemodialysis treatment of 3-5 hr.