M. Sankar

Microspheres are characteristically spherical and free flowing powders having particle size ranging from 1-1000 μm consisting of proteins or synthetic polymers. Microspheres are free flowing solid particle made up of biodegradable and non-biodegradable components Microspheric drug delivery system has wide range of application as it covers targeting the drug to particular site to imaging and helping the diagnostic features. Microspheres form an essential part of novel drug delivery systems. Microspheres reduce the dosing frequency and improve patient compliance by designing and evaluating Sustained Release microspheres for effective control of many chronic diseases. A well designed controlled drug delivery system can overcome some of the problems of conventional therapy and enhance the therapeutic efficacy of a given drug. There are various approaches in delivering a therapeutic substance to the target site in a sustained controlled release fashion. A Microsphere has its drug dispersed throughout the particle i.e. the internal structure is a matrix of drug and polymeric excipients. The objective of this article is to emphasize on the principles underlying the development and evaluation of microspheres as a controlled and targeted drug delivery system.

A simple RP-HPLC compatible method for the injectable suspension dosage of combined medroxyprogesterone acetate and estradiol cypionate was developed and validated according to ICH and USP guidelines. The chromatographic separation was achieved by using the Zorbax Eclipse C18 column (50 mm×4.6 mm, 2.7 µm) with gradient elution technique at a flow rate of 1.0 ml/min. The UV detection was performed at 225 nm. The linearity of medroxyprogesterone acetate over the concentration range was 49.65 to 744.69 μg/ml and 10.15 to 152.28 μg/ml for estradiol cypionate respectively. The accuracy was evaluated by means of spike recovery method and the result showed in the range of 99.7% to 101.4% for medroxyprogesterone acetate and 98.6% to 101.8% for estradiol cypionate. The specificity of the method showed that the analyte was not interfered by the presence of co-formulated substances. The robustness of the study was found agreeable; hence it proves that the method was robust. The stability of the analyte was found stable for 24 hours. The developed method was successfully employed for the determination of combined medroxyprogesterone acetate and estradiol cypionate in injectable suspension dosage forms.