Formulation and evaluation of ketorolac tromethamine-loaded albumin microspheres for potential intramuscular administration

The objective of this work was to prepare and evaluate ketorolac tromethamine- loaded albumin microspheres using a factorial design. Albumin microspheres were prepared by emulsion cross-linking method. Selected formulations were characterized for their entrapment efficiency, particle size, surface morphology, and release behavior. Analysis of variance ( ANOVA) for entrapment efficiency indicated that entrapment efficiency is best fitted to a response surface linear model. From the statistical analysis it was observed that as the drug: polymer (D:P) ratio and volume of glutaraldehyde increased, there was a significant increase in the encapsulation efficiency. Scanning electron microscopy of the microspheres revealed a spherical, nonporous and uniformappearance, with a smooth surface. Based on the entrapment efficiency and physical appearance, 9 formulations were selected for release study. The maximum particle size observed was below 40 mu m. The release pattern was biphasic, characterized by an initial burst effect followed by a slow release. All selected microspheres, except those having less polymer proportion (D:P ratio is 1: 1), exhibited a prolonged release for almost 24 hours. On comparing r(2) values for Higuchi and Peppas kinetic models, different batches of microspheres showed Fickian, non- Fickian, and diffusion kinetics. The release mechanism was regulated by D: P ratio and amount of cross-linking agent. From the experimental data obtained with respect to particle size and extent of drug release, it could be concluded that the prepared microspheres are useful for once-a-day intramuscular administration of ketorolac tromethamine.