Influence of Carbopol 71G-NF on the release of dextromethorphan hydrobromide from extended-release matrix tablets

The objective of this study was to evaluate the potential of Carbopol(®) 71G-NF on the release of dextromethorphan hydrobromide (DM) from matrix tablets in comparison with hydroxypropyl methylcellulose (HPMC(®) K15M) and Eudragit(®) L100-55 polymers. Controlled release DM matrix tablets were prepared using Carbopol 71G-NF, HPMC K15M, and Eudragit L100-55 at different drug to polymer ratios by direct compression technique. The mechanical properties of the tablets as tested by crushing strength and friability tests were improved as the concentration of Carbopol, HPMC, and Eudragit increased. However, Carbopol-based tablets showed a significantly (P<0.05) higher crushing strength and a lower friability than HPMC and Eudragit tablets. No significant differences in weight uniformity and thickness values were observed between the different formulations. It was also found that Carbopol significantly (P<0.05) delayed the release of DM in comparison with HPMC K15M and Eudragit L100-55. A combination of HPMC K15M and Eudragit L100-55 in a 1:1 ratio at 20 and 30% significantly (P<0.05) delayed the release of DM than Eudragit L100-55 alone. Moreover, blends of Carbopol and HPMC at a 1:1 ratio at the 10, 20, and 30% total polymer concentration were investigated. The blend of Carbopol and HPMC at 10% level significantly (P<0.05) slowed the release of DM than Carbopol or HPMC alone, whereas blends at 20 and 30% level significantly (P<0.05) delayed the release of DM compared with HPMC or Carbopol alone. The results with these polymer blends showed that it was possible to reduce the total amount of polymers when used as a combination in formulation.