Acta Pharm. 51 (2001) 53-62
A simple dry coating process for the formulation of enteric-release dosage forms was developed. Hydroxypropylmethylcellulose phthalate (HPMCP), cellulose acetate phtalate (CAP), polyvinylacetate phtalate (PVAP), hydrogenated castor oil (HCO) and polyvinylmethylether-maleic anhydride copolymer (PVM/MA) were investigated as dry coating agents. Diclofenac-sodium-polymer mixtures in different ratios, from 1:0.05 to 1:3, were prepared using Tubula mixer. X-ray diffraction patterns showed that there was no drug-polymer interaction, whereas DSC patterns indicated that the drug surface was covered with the polymer and that 30 minutes was the optimal mixing time. The prepared coated mixtures were filled into hard gelatin capsules. Release studies revealed that the release rate of the drug decreased with increased concentration of the polymer in the coated mixture. The dry coated drug and polymer mixtures in the ratios of 1:3, 1:1, 1:0.1, 1:0.25 and 1:1 for PVM/MA, HPMCP, HCO, CAP and PVAP, respectively, gave products of optimal enteric and sustained release characteristics compared to a commercial product. Release kinetics studies showed that the drug release followed the zero-order model.
Keywords: dry coating method, diclofenac sodium, polymers, enteric-release capsules, release studies, kinetics