Biopharmaceutic and pharmacokinetic studies on piroxicam suppositories
Abstract
Two suppositories of piroxicam (Pir) with different bases, a fat base (FB) and a hydrophilic base (PEG), were studied for the sake of avoiding gastrointestinal irritation.
Their bioavailabilities in rabbits and in 10 volunteers were compared with that of conventional tablets in order to determine whether application of Pir would result in a comparably high systemic bioavailability. FB is composed of semi-synthetic fatty acid esters: PEG is a mixture of different polyethylene glycols.
The serum concentration was determined by HPLC. The sensitivity was 0.05 microg/ml in serum with the linearity between 0.1 and 25 microg/ml. No interferences were found from endogenous compounds or other commonly used anti-inflammatory agents.
It was found that the release % of the 2 Pir suppositories in vitro were related to the absorption % in vivo by following regression equations:
Y=-0.3504+6.788X and
Y=47.83+/-1.706X
It was fitted to a one-compartment pharmacokinetic model. The bioavailability of Pir by rectal route is practically the same as that by oral route. In man, after 20 mg, the AUC were 126 microg.h/ml for PEG suppository, 123 microg.h/ml for FB suppository, and 140 microg.h/ml for tablet. Lack of significant difference indicates a bioequivalence between the 2 suppositories and the tablet. The long half life of Pir in different dosage forms studied in men (43+/-6 h) was very close to the data reported by Schiantarelli et al.
This study showed that the 2 suppositories of Pir gave good bioavailabilities without local irritation to the rectal mucosa. We recommend to use Pir suppository instead of oral tablets in long term therapy.
Keywords:
Their bioavailabilities in rabbits and in 10 volunteers were compared with that of conventional tablets in order to determine whether application of Pir would result in a comparably high systemic bioavailability. FB is composed of semi-synthetic fatty acid esters: PEG is a mixture of different polyethylene glycols.
The serum concentration was determined by HPLC. The sensitivity was 0.05 microg/ml in serum with the linearity between 0.1 and 25 microg/ml. No interferences were found from endogenous compounds or other commonly used anti-inflammatory agents.
It was found that the release % of the 2 Pir suppositories in vitro were related to the absorption % in vivo by following regression equations:
Y=-0.3504+6.788X and
Y=47.83+/-1.706X
It was fitted to a one-compartment pharmacokinetic model. The bioavailability of Pir by rectal route is practically the same as that by oral route. In man, after 20 mg, the AUC were 126 microg.h/ml for PEG suppository, 123 microg.h/ml for FB suppository, and 140 microg.h/ml for tablet. Lack of significant difference indicates a bioequivalence between the 2 suppositories and the tablet. The long half life of Pir in different dosage forms studied in men (43+/-6 h) was very close to the data reported by Schiantarelli et al.
This study showed that the 2 suppositories of Pir gave good bioavailabilities without local irritation to the rectal mucosa. We recommend to use Pir suppository instead of oral tablets in long term therapy.