Acetazolamide is a diuretic whose main action is the inhibition of carbonic anhydrase . Mild acidosis in the brain may be the mechanism by which the drug exerts its antiseizure activity; alternatively, the depolarizing action of bicarbonate ions moving out of neurons via GABA receptor ion channels may be diminished by carbonic anhydrase inhibition. Acetazolamide has been used for all types of seizures but is severely limited by the rapid development of tolerance, with return of seizures usually within a few weeks. The drug may have a special role in epileptic women who experience seizure exacerbations at the time of men-ses; seizure control may be improved and tolerance may not develop because the drug is not administered continuously. The usual dosage is approximately 10 mg/kg/d to a maximum of 1000 mg/d.Another carbonic anhydrase inhibitor, sulthiame, was not found to be effective as an anticonvulsant in clinical trials in the USA. It is marketed in a number of other countries.