Improvement of drug release rate from carbopol 934P formulation

Carbopol 934P (CP) is a mucoadhesive polymer which has been investigated as a useful adjuvant for bioadhesive drug delivery system. However, since the drug release rate from the solid formulation of CP is slow, it is difficult to take advantage of the polymer's mucoadhesive property in oral administration of fast-acting drugs. In this study, we prepared freeze-dried sodium salt of CP (FNaCP) in order to improve drug release from the formulation of CP. The drug release rate from the formulation of FNaCP was much faster than that of CP: the rate from the formulation of CP in JP XIII 1st fluid (pH 1.2) was faster than in JP XIII 2nd fluid (pH 6.8). To determine the cause of rapid drug release from FNaCP capsules, the change of CP gel properties with pH and ionic strength was investigated. Experimental results indicated that CP forms a swollen gel layer, a drug release barrier between the formulation of CP and the bulk release media. FNaCP was also thought to disperse rapidly in the 1st and 2nd fluids without formation of the swollen gel layer. In conclusion, since FNaCP improves the drug release rate from the solid CP formulation, it could be a useful adjuvant of an oral bioadhesive drug delivery system.