Release and rectal absorption of ethosuximide from suppositories in rabbits

Ethosuximide was formulated in different suppository bases. In vitro release experiment demonstrated more rapid and higher release of the drug from water soluble polyethylene glycol (PEG) bases than from Witepsol fatty bases. Rectal administration in PEG 400:4000 and 400:6000 to rabbits gave high plasma levels where Cmax was 45.66 and 42.66 micrograms.ml-1, respectively; while, in the presence of Witepsol E76 and W35 it was 34.00 and 28.33 micrograms.ml-1, respectively. The systemic availability was 89.39%, 82.72%, 58.80% and 47.45% when the bases were PEG 400:4000, PEG 400:6000, Witepsol E76 and Witepsol W35, respectively.