Development and in-vitro evaluation of controlled release multiparticulates of theophylline

A multiparticulate system was developed using the coating pan method with nonpareil seed as the core material for the Theophylline. The drug loaded pellets were prepared by powder layering technique, sprinkling the drug on the nonpareil seeds using PVP K-30 in IPA as binder. The drug loaded pellets were coated by using polymers ethyl cellulose, EUDRAGITRS:RL (2:1) and EUDRAGIT® RS:RL (3:1). The fraction of coated pellets were collected on the basis of percentage of coating 5%, 10%, 15% and 20% and evaluated for in-vitro release studied using USP dissolution apparatus. The pellets coated with 15% ethyl cellulose, 15% &20% EUDRAGIT RS: RL (3:1) shows release profiles as per USP for 12 hours dosing. Product coated with EUDRAGITRS: RL (2:1) were unable to retard release of drug in at same percentage of coating on dry basis. Mathematical models like zero-order, firstorder, Korsmeyer – Peppas and Higuchi were applied in kinetic studies of theophylline release from the formulated pellets. All the products of theophylline coated pellets are best fitted model for Higuchi and Korsmeyer – Peppas. The mechanism of drug release analyzed by evaluating n-values derived from model fitting, range between 0.5 and 1.0, except SL2:105 and SL3:115, which indicates that drug release is a consequence of anomalous mass transport processes occurring within these dosage forms. This implies that drug release from matrices is both diffusion and swelling controlled which deviates from Ficks 2nd law of diffusion. Scanning electron microscopy study revealed that the microspheres were spherical and porous in nature.