Utilization of Natural Olibanum Gum Resin as a Rate Controlling Polymer in Design and Evaluation of Microspheres of an Antiretroviral Drug by using a Unique Spray Drying Technique

Olibanum gum resin was evaluated as rate controlling agent and to prepare resin-coated microspheres. Zidovudine (AZT), an anti-retroviral drug was selected as novel drug for the experiment. Resin coated microspheres of AZT were prepared by spray drying technique using olibanum gum resin as a rate controlling polymer and the microspheres were evaluated. The resin-coated microspheres were spherical, discrete, free flowing and multinucleate monolithic type. The mean size range was found for formulation D: P1, D: P2, D: P3 in the range of 16.88, 18.51, and 21.72 μm respectively. Entrapment efficiency was in the range of 67.41 to 80.32%. The FTIR and DSC study confirmed that no chemical interaction took place during entrapment process. The X-ray diffraction study indicates the amorphous dispersion of the drug after entrapment into microspheres. The effect of polymeric resin on release profile of drug was calculated. AZT release from the resin coated microspheres was slow over 24 hr and dependant on core: coat ratio, and size of microspheres. Drug release was by non-fickian diffusion mechanism. Good linear relationships were observed between core: coat ratio of the microspheres and release rate. Resin-coated microspheres of AZT exhibited good controlled release characteristics and were found suitable for once a day oral controlled release products.