Enteric-coating of HPC capsules prepared by Injection-Molding

Purpose. To evaluate injection molded (IM) hydroxypropyl cellulose (HPC)-based capsules as cores for the application of a pH-dependent soluble coating, in comparison with conventional capsules. Methods IM (BabyPlast 6/10P, Cronoplast S.L.) formulation consisted of a 90:10 HPC (Klucel® LF, Ashland):polyethylene glycol 1500 blend. Size 0 gelatin and hydroxypropyl methylcellulose (HPMC) capsules (Capsugel) and the IM HPC-based capsules were filled with 80 mg of acetaminophen. Aqueous solutions of the same materials were used for sealing the capsule shells. Capsules were coated (Hi-coater, Vector Corporation LDCS, equipped with a perforated pan) with a Eudragit® L 30 D55 (64.10):TEC (3.85):deionized water (32.05) suspension. Samples of sealed and unsealed capsules with theoretical weight gains of 0, 4, 6, 8, 10 mg of dry polymer/cm2 were withdrawn and imaged by scanning electron microscopy (SEM). The Dissolution Test for Delayed-Release Dosage Forms (USP 34) was used for evaluating the release performance and the amount of drug released was determined by UV/Vis spectrophotometry at 248 nm. Results Initially gelatin, HPMC and HPC were coated simultaneously in a single pan; actual polymer deposition was not linear to theoretical weight gain likely due to different capsules shell weight and so HPC ones were coated separately (same coating parameters). The release performance demonstrated no need for sealing the HPC-based cores. Different from gelatin and HPMC capsules, the lag time (time to 10% drug release) from HPC ones increased as a function of the amount of polymer applied, up to ~168 min; moreover, samples with the maximum level of coating were able to withstand the acidic medium and release the drug after the pH change within a time analogous to the lag time of uncoated IM cores. Conclusion Molded HPC-based capsules could successfully coated with an enteric polymer; this gastroresistant pulsatile-delivery device has promise for further developing into a colonic delivery system.