Posovolone (Co 134444) is an orally active, neuroactive steroid. Posovolone has anticonvulsant and anxiolytic-like activity as well as ataxic effects.In Vitro: In mice, Co 134444 (0.5-10 mg/kg, IP, 15 min; 1-60 mg/kg, PO; 30 min) demonstrates efficacy against pentylenetetrazol (PTZ)-induced seizures with an ED50 of 3.3 mg/kg after IP administration and 9.8 mg/kg orally. Similarly, protection against maximal electroshock (MES) is observed with an ED50 of 4.8 mg/kg IP and 20.6 mg/kg PO. In rats, Co134444 (10-40 mg/kg; PO; 30 min) protects against PTZ-induced seizures and MES-induced seizures with an ED50 of 23.6 mg/kg and 25.3 mg/kg, respectively.