Influence of oral adsorbent AST-120 on anticonvulsive effect of zonisamidein rats

The influence of oral adsorbent AST-120 (Kremezin) on the anticonvulsive ef fect and pharmacokinetics of zonisamide was investigated. Oral administrati on of zonisamide (50 mg/kg) blocked the appearance of the tonic extension i nduced by maximal electroshock seizure. This effect of zonisamide was inhib ited by the oral coadministration of AST-120 (5 g/kg). In pharmacokinetics study, the serum zonisamide concentration after coadministration of zonisam ide and AST-120 was significantly lower than that of single administration of zonisamide. However, the anticonvulsive effect of zonisamide was not aff ected by the administration of AST-120 1.5 h after zonisamide administratio n. In this condition, the serum zonisamide concentration was not changed. I n the in vitro study, AST-120 completely adsorbed zonisamide. These finding s suggest that when AST-120 is administered concurrently with zonisamide, a significant inhibition of the anticonvulsive effect of zonisamide occurs, and the decrease in serum zonisamide concentration by the adsorption effect of AST-120 is related to this phenomenon. (C) 2001 Elsevier Science Inc. A ll rights reserved.