Study of drug release from pellets coated with Surelease containing hydroxypropylmethylcellulose

The release of metoclopramide hydrochloride (a very water soluble cationic drug) and diclofenacc sodium (a sparingly soluble anionic drug)from pellets coated with Surelease containing hydroxypropylmethylcellulose (HPMC) at di fferent coating loads was investigated. The release rates of either drug at each coating composition decreased as the coating load increased. Inclusio n of HPMC E15 increased the release rates of both drugs compared to pellets coated only with Surelease. This was thought to be due to the leakage of t he soluble part of the film (HPMC E15) during dissolution, which left pores for drug release. The Surelease:HPMC E15 ratio had a major role in the rel ease rates of drugs. Addition of HPMC E15 into Surelease did not change the release mechanism for metoclopramide hydrochloride (the mean value of n ap proximate to 0.57) from that of Surelease alone, and diffusion remained the main mechanism controlling the release. However the release exponent(appro ximate to 1.28) increased for diclofenac sodium on addition of HPMC E15, in dicating a dissolution controlled mechanism. Despite its lower water solubi lity, diclofenac sodium was released slightly faster than metoclopramide hy drochloride from pellets coated with Surelease containing HPMC E15 at equiv alent coating loads.