Study on the Formulation of Pantoprazole Microspheres and Tablets Using Mucuna Pruriens Starch

Abstract

Microsphere drug delivery systems are used to protect sensitive drugs from enzymatic degradation in the body, for controlled release and tissue targeting of the drug of interest. Starch and products derived from starch modification, are increasingly gaining acceptance in microsphere drug delivery. They are less expensive, non-toxic, readily available, bio-compatible and bio-degradable. The aim of the study was to formulate sustained release pantoprazole microspheres and enteric-coated tablets using MPS. The specific objectives of the study were (i) modification of MPS by cross-linking with glutaraldehyde, (ii) formulation of pantoprazole microspheres and tablets (iii) evaluation of the entrapment efficiency, particle size, mucoadhesive, swelling and in vitrorelease properties of the microspheres and (iv) evaluation of the tablet properties formulated. MPS was extracted from the dried, pulverized endosperm of the dehulled seed of Mucuna pruriens utilislegume. The phytochemical analyses were performed on powdered MPS samples extracted. The samples were processed and the powder properties determined by standard Pharmacopoeial methods. MPS powder properties were compared with those of maize starch (MS) and cassava starch (CS). MPS was modified by heat treatment at 67.5 0C and used to prepare MPS flakes. The flakes were used to prepare MPS microspheres by emulsion cross-linking using glutaraldehyde as the cross-linking agent. Cross-linking time was varied between 10-180 min and the MPS microspheres prepared were characterized for particle size, swelling index and mucoadhesion. Photomicrographs of the MPS microspheres prepared were obtained. The MPS microspheres were loaded with pantoprazole and evaluated for mean particle size, trapping efficiency, mucoadhesion, and drug release profiles in both Simulated Gastric Fluid (SGF, pH=1.2) and Simulated Intestinal Fluid (SIF, pH=7.2). The pantoprazole microspheres were tabletted by the wet granulation method and tablet properties evaluated included: assay for pantoprazole content, weight uniformity, hardness, friability, disintegration and dissolution. Pantoprazole release in SGF and SIF were performed in a dissolution apparatus, using the basket type method and the content was assayedspectrophotometrically at 278 nm and 289 nm respectively. Pantoprazole release from the tablet formulations was fitted to the Korsmeyer-Peppas and Higuchi’sdiffusion model equations to elucidate and interprete drug release mechanism. Data analyses were performed by both descriptive and inferential statistics. The inferential analysis was done using GraphPadInStat Demo. Phytochemical analyses of Mucuna pruriens utilis showed the presence of alkaloids, flavonoids, saponins, carbohydrates, resins and protein. Fat, oil, reducing sugar, tannins, and steroids were not detected. MPS microspheres cross-linked for 120 min had the highest entrapment efficiency of 81.3±1.40 % compared to an entrapment efficiency of 56.1±1.40 % for those cross-linked for 10 min only. Pantoprazole release from the microspheres was higher in SIF than in SGF. The release exhibited the triphasic pattern typical of microspheres. Representative plots of the Higuchi and Korsmeyers-Peppasequation for the release of pantoprazole in both SIF and SGF showed that the mechanism of drug release from the microspheres was complex and involved drug diffusion, desorption and surface erosion. The release mechanism obtained for microspheres cross-linked for 30 and 90 min in SGF and, cross-linked for 20, 30, 150 and 180 min in SIF, depicted non-Fickian(anomalous) diffusion model (0.43<n<0.85). Microspheres cross-linked for 10 min, and tested in SGF, depicted Super case II transport, (n=0.85). There was significant difference (P˂ 0.05) in drug release in SIF and SGF with release higher in SIF. Such release was high for the acid labile drug in the simulated alkaline pH of the intestine. Pantoprazole tablets coated with cellulose acetate phthalate were completely insoluble in SGF (pH=1.2) and soluble in SIF (pH=7.2), which is desirable for the drug pantoprazole since it is acid labile. The in vitro release mechanism of pantoprazole from selected coated tablets fitted the diffusion model. The release in SIF was first order diffusion as indicated by high R2 values (R2 ˃0.99), which when fitted into the Korsmeyers-Peppas model, the release was non-Fickian (anomalous) diffusion model, (0.43<n<0.85). Statistically, there was a significant difference (P< 0.05) in pantoprazole release.