Anticonvulsant properties of ropizine in epileptic and nonepileptic beagle dogs

Studies were conducted on a colony of purebred beagle dogs. Animals with spontaneous seizures were classed as epileptic beagles (EB). Those without spontaneous seizures were termed nonepileptic beagles (NEB). The median convulsant current for maximal electroshock seizure (MES) threshold was 175(194-158)mA for EB and 390 (417-364) mA for NEB. Similarly the median convulsant dose of pentylenetetrazol (PTZ) was 7.9 (10.1-6.2) mg/kg for EB and 20.2 (24.2-17.6) mg/kg for NEB. Following pretreatment with graded doses of ropizine (SC 13504), the median protective dose against MES was 6.0(9.2-3.9) mg/kg in EB and 3.2(4.8-2.1) mg/kg in NEB. Based on the incidence of ataxia, EB had a median toxic dose (TD50) of 14.0(16.5-11.9) mg/kg, while in NEB it was 18.0(23.6-13.7)mg/kg. The TD50 doses were unable to protect against a convulsive dose of PTZ. It is concluded first that ropizine may have anti-grand mal activity but apparently lacks an anti-petit mal action. Secondly, EB are more sensitive than NEB to the convulsive effects of electric current and PTZ, yet less responsive to the anticonvulsant actions of ropizine.