Sustained-release phenylpropanolamine hydrochloride bilayer caplets containing the hydroxypropylmethylcellulose 2208 matrix. I. Formulation and dissolution characteristics.

The purpose of this study was to develop a new sustained-release phenylpropanolamine hydrochloride (PPA) bilayer caplets that consists of an immediate-release portion and a prolonged-release portion containing a hydroxypropylmethylcellulose 2208 (HPMC2208) matrix. Since PPA is a highly water-soluble drug, incorporation of 60% HPMC2208 level in the matrix was required for giving the product a PPA-slow releasing property. Difference in the viscosity grade of HPMC2208 in the matrices did not greatly influence the PPA dissolution characteristics from the matrices. Therefore, we formulated the prolonged-release portion consisting of 10% PPA, 30% excipients, and 60% HPMC2208 (Metolose 90SH4000) into the sustained-release PPA bilayer caplets. The PPA dissolution characteristics from the formulated bilayer caplets showed the prolonged dissolution profile after rapid dissolution and was close to the targeted profile calculated from PPA pharmacokinetics study. The manufacturing methods of the prolonged-release portion and the filling order of the prolonged-release portion in bilayer compression did not significantly affect the PPA dissolution characteristics from the bilayer caplets. The PPA dissolution characteristics from the bilayer caplets was pH independent. Moreover, the PPA dissolution characteristics from the bilayer caplets was not affected by mechanical shear. The sustained-release PPA bilayer caplets is expected to present constant prolonged-release of PPA after rapid dissolution in vivo without dissolution change due to pH and mechanical shear.