EXCIPIENT INTERACTION WITH CETYLPYRIDINIUM CHLORIDE ACTIVITY IN TABLET BASED LOZENGES

Purpose. The purpose of the investigation was to determine the effect of tablet excipients on the activity of cetylpyridinium chloride (CPC) and the relative interaction between excipients and CPC. Methods. An analytical assay was developed to evaluate the interaction between CPC and the excipients. In vivo activity was investigated using six volun teers by determining the reduction in colony forming units recoverable from the oropharynx after sucking each proprietary lozenge separately on different days. In vitro determinations investigated the relative antimicrobial activity of aqueous solutions of the lozenges and, the e ffect of pK and tablet base excipients on that activity against Staphy lococcus aureus, Streptococcus pyogenes and Candida albicans. Results, Both in vivo and in vitro results showed that the tablet based lozeng es had markedly reduced antimicrobial activities compared with previou s results with a candy based lozenge (in vivo and in vitro) or the sam e concentration of aqueous CPC (in vitro). Magnesium stearate suspensi ons in CPC 250 mu g/ml indicated that magnesium stearate adsorbed CPC and at 0.4% lozenge weight and above significantly reduced the antimic robial activity of CPC 250 mu g/ml. Conclusions. The reduced activity of CPC in tablet based lozenges resulted from a decreased availability of CPC in solution due to an adsorption of CPC on magnesium stearate. To avoid this reduction in activity tablet based lozenges containing CPC 250 mu g/ml, or similar concentrations, plus magnesium stearate sh ould contain not more than 0.38 w/w lozenge weight of the lubricant.