Purpose: To formulate prolonged-release floating microparticles that would minimise the irritant effect of weakly acidic drugs, such as nimesulide, on the stomach by avoiding direct contact with gastric mucosa.

Methods: Sustained release floating microparticles of nimesulide was prepared by a coacervation (non-solvent addition technique. Three different ratios of the coacervating polymer, low-viscosity hydroxypropyl methylcellulose (HPMC), were used, and the dissolution characteristics of the floating microparticles in simulated gastric and intestinal media were evaluated. In order to determine whether there was drug – polymer interaction, the microparticles were also assessed by infra-red (FTIR) spectroscopy and x-ray diffraction (XRD). Micromeritic properties of the microparticles were also assessed.

Results: The drug content of the floating microparticles increased with increase in the level of HPMC incorporated. All floating microparticles formulations showed good flow properties while particle size analysis revealed that the appearance and size distribution of the formulations varied with polymer concentration. FTIR and XRD data indicated the crystalline nature of the drug but there was no chemical interaction between the drug and the polymer in the microparticles. Nimesulide release was faster in simulated intestinal fluid (pH 6.8) than in simulated gastric fluid (pH 1.2) and distilled water (pH 6.5).

Conclusion: Coacervation non-solvent addition is a suitable technique for preparing floating microparticles of nimesulide using low-viscosity HPMC.