Hemodialysis clearance of ethosuximide in patients with chronic renal disease.

Clearance of ethosuximide by hemodialysis was studied. Four patients with chronic renal disease supported by hemodialysis were given ethosuximide 500 mg four hours before dialysis. Samples of arterial and venous blood and dialysate were collected before and during the four-hour dialysis procedure. Ethosuximide concentration was measured by gas-liquid chromatography. The extraction efficiency for the dialysis systems used in this study ranged from 61.1 to 100%, and dialysis clearance was from 122.3 to 156.3 ml/min. Recovery of ethosuximide from the dialysate was 38.8 to 52.4% of the administered dose. Hemodialysis reduced the elimination half-life of ethosuximide from a presumable value of 55 hours to an average of 3.5 hours. The authors concluded that ethosuximide is dialyzable. Hemodialysis patients concurrently receiving ethosuximide may require a supplemental dose or an altered ethosuximide dosing schedule. Because hemodialysis quickly clears ethosuximide, it may be useful in treating ethosuximide overdosage.