Enhancing Effect of Glyceryl-1-monooctanoate on the Rectal Absorption of Gentamicin from Hollow-Type Suppositories in Rabbits

Abstract

A hollow-type suppository containing gentamicin (GM) in its cavity was prepared using Witepsol H-15 (H-15) mixed with glyceryl-1-monooctanoate (MO) or MO alone in the body of the suppository (type I) and a suppository (type II) containing GM and MO in the cavity was constructed using H-15 in the body of the suppository.Without MO, GM (60 mg) was not absorbed (plasma GM levels less than 1μg/ml). However, the absorption of GM from the rectum of rabbits was enhanced by coadministered MO in types I and II. Even when the amount of GM was decreased to 6mg (1/10), GM was observed in the plasma (C_max, 3.5±0.3μg/ml) after administration of the suppository made from MO mixed with H-15. The enhancing effect of MO on the rectal absorption of GM could not be further increased by incorporating an amount of MO larger than approximately 300mg into the suppository.This study demonstrates that MO can be used in the two types of hollow suppositories as an effective enhancing agent of rectal absorption of poorly absorbed drugs such as GM.