Anticonvulsant effects of benzhydryl piperazines on maximal electroshock seizures in rats

The anticonvulsant effects of four benzhydryl piperazines, SC-13504 (ropizine, an anticonvulsant), hydroxyzine (HDX, an anxiolytic), chlorcyclizine (CCZ, an antihistaminic) and buclizine (BUC, an antihistaminic), were investigated utilizing a modified maximal electroshock seizure test in rats. In addition to detecting the presence or absence of tonic hindlimb extension, the modified method quantified various phases of the seizure. All four benzhydryl piperazines exhibited anticonvulsant activity in maximal electroshock seizure, but SC-13504 was similar in efficacy to phenobarbital and phenytoin, and much more effective than HDX, CCZ or BUC. Additionally, SC-13504 possessed a therapeutic index much greater than any of the compounds tested. The duration of action of the benzhydryl piperazines, in hours was: SC-13504, 0.5 to 8; HDX, 0.5 to 2; CCZ, 0.5 to 16; and BUC, 2 to 8. Buc and CCZ are postulated to be converted to active anticonvulsant metabolites.