Preparation and evaluation of sustained release dosage forms for posttransplant care

Abstract

Aim: The purpose of the study was to prepare and characterize microbeads for oral sustained release of tacrolimus. Design, methodology, and approach: Tacrolimus-based microbeads were developed by ionic gelation method. Xanthan gum, chitosan, and sodium alginate were used as polymers for aqueous internal phase using calcium chloride as a cross-linking agent. The microbeads were evaluated for morphologic features by scanning electron microscopy, percentage yield, drug entrapment, and in vitro drug release. Findings and implications: Microbeads were examined for the effects of various variables in formulation process. The cross-linking reaction between sodium alginate and calcium chloride for being converted into calcium alginate in the formulation process was used in the microencapsulation of tacrolimus core material. The results showed the compatibility of the drug with the polymers in the formulation as observed in Fourier-transform infrared spectroscopy studies. The formulated microbeads showed high percentage yield and drug entrapment efficacy and the optimized formulation showed a delayed release effect following zero-order mechanism of release. Conclusion: Ionotropic gelation method was found to be a suitable method for preparing tacrolimus microbead-sustained-release drug delivery system. Chitosan and xanthan gum polymers showed potential in aiding the formulation of sustained release tacrolimus microbeads. Xanthan gum is soluble in water and confers high viscosity at low concentrations. The molecular weight of xanthan gum is more than the chitosan polymer which leads to better sustained release of microbeads prepared with xanthan gum compared to chitosan microbeads. Both chitosan and xanthan gum microbeads followed zero-order-release kinetic models.