Metformin hydrochloride suppositories (500mg) were prepared using four
suppository bases. The prepared suppositories were evaluated with reg
ard to physicochemical properties, release characteristics and their e
ffects on the histological and cytological structure of the rat rectal
mucosa. The in vitro release of most of the prepared suppositories wa
s found to be rapid and, in some formulations, even faster than that o
f 500 mg metformin hydrochloride commercial tablets. On the other hand
, the prepared suppositories showed no induced harmful effects on the
fine structure of the rat rectal mucosa.