The invention relates to 3a-ethynyl, 3ß-hydroxy, 5a-pregnan-20-oxime or a pharmaceutically acceptable salt thereof, which compounds and/or salts are useful as modulators of the mammal brain excitability via the gamma-5 aminobutyric acid receptor-chloride ionophore (GABAA-R) complex and in the treatment of disorders such as hepatic encephalopathy, Down's syndrome and Alzheimer's disease.