Effect of a pharmaceutical cationic exchange resin on the properties of controlled release diphenhydramine hydrochloride matrices using Methocel K4M or Ethocel 7cP as matrix formers.

This work was aimed at evaluating the effect of a pharmaceutical cationic exchange resin (Amberlite IRP-69) on the properties of controlled release matrices using Methocel K4M (HPMC) or Ethocel 7cP (EC) as matrix formers. Diphenhydramine hydrochloride (DPH), which was cationic and water soluble, was chosen as a model drug. HPMC- and EC-based matrices with varying amounts (0-40%w/w) of resin incorporation were prepared by a direct compression. Matrix properties including diameter, thickness, hardness, friability, surface morphology and drug release were evaluated. The obtained matrices were comparable in diameter and thickness regardless of the amount of resin incorporation. Increasing the incorporated resin decreased the hardness of HPMC- and EC-based matrices, correlating with the degree of rupturing on the matrix surfaces. The friability of HPMC-based matrices increased with increasing the incorporated resin, corresponding to their decreased hardness. In contrast, the EC-based matrices showed no significant change in friability in spite of decreasing hardness. The incorporated resin differently influenced DPH release from HPMC- and EC-based matrices in deionized water. The resin further retarded DPH release from HPMC-based matrices due to the gelling property of HPMC and the ion exchange property of the resin. In contrast, the release from EC-based matrices initially increased because of the disintegrating property of the resin, but thereafter declined due to the complex formation between released drug and dispersed resin via the ion exchange process. The release in ionic solutions was also described. In conclusion, the incorporated resin could alter the release and physical properties of matrices.