Rme. Richards et al., EXCIPIENT INTERACTION WITH CETYLPYRIDINIUM CHLORIDE ACTIVITY IN TABLET BASED LOZENGES, Pharmaceutical research, 13(8), 1996, pp. 1258-1264
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.