Pharmaceutical study of suppository formulations for improved in vivo kinetics of rifampicin.

PURPOSE

To study rifampicin (RFP) suppository formulations that were prepared by adding an absorption promoter and a holding agent to conventional rifampicin suppositories in order to achieve higher blood drug levels.

SUBJECTS AND METHODS

The subjects were 3 healthy volunteers who gave consent to participate in this study. Suppository formulations were prepared by adding sodium caprinate (the absorption promoter) to 600 mg, 750 mg, or 900 mg of RFP at about 3% of the suppository weight and sodium alginate (the holding agent) at 25% of the RFP content. Serum samples collected at 2, 6, and 10 hours after insertion of a suppository were subjected to RFP concentration analysis.

RESULTS

In subject no. 1, the maximum concentration was 0.807 Lg/ml, 1.093 microg/ml, and 1.291 microg/ml after administration of a suppository containing 600 mg, 750 mg, or 900 mg of RFP, respectively.

DISCUSSION

Since an injectable RFP formulation has not been approved in Japan, formulation studies of RFP suppositories are important to achieve a better clinical response and to prevent the development of resistance. The present formulation that delivered a blood concentration of RFP considerably higher than 1 microg/ml was considered to have therapeutic potential. Its clinical utility will be examined in further formulation studies.