Absorption and bioavailability of diclofenac after rectal administration of diclofenac-na gel preparation in rat and man.

In order to evaluate diclofenac-Na (DC-Na) micro-enema, DC-Na gel preparations were administered to rats and man. When DC-Na gel preparations were rectally administered at various pH (pH 5- 8) to rats, their bioavailability increased at higher pH. The bioavailability of DC-Na gel preparations (pH 8.0) in rats was significantly higher than that with conventional suppository bases, Witepsol H-15 and polyethylene glycol 1000 (PEG 1000). In man, the DC-Na gel preparation showed higher Cmax and higher bioavailability than commercial suppository made with an oily base. DC-Na gel preparations containing 10% v/v oleic acid showed a prolonged action. The irritative effect of DC-Na gel preparation on rectal mucosa in rats was weaker than that of PEG 1000, but similar to that of Witepsol H-15. Therefore, the present results suggest that gel preparation is a favorable form for rectal administration of diclofenac-Na.