NAPROXEN INCORPORATED LIPID EMULSIONS - I - FORMULATION AND STABILITYSTUDIES

Background: Intravenous lipid emulsions stabilized with phospholipids have been an attractive alternative as vehicles for drug delivery, par ticularly for the parenteral administration of drugs with solubility p roblems. Methods: Naproxen (a poorly aqueous soluble nonsteroidal anti -inflammatory agent) emulsions were formulated with different types of emulsifiers (soybean lecithin, synperonic PEF-127 and a 50:50 mixture of these). The stability of the various emulsion systems was evaluate d at different temperatures (4, 25 and 40 degrees C) for a period of 6 months by measuring changes in pH, droplet size, viscosity and percen tage oil separation. The percentage of naproxen incorporation and the degree of haemolysis induced by the different types of emulsion system s was also determined. Results: The emulsifier type showed a pronounce d effect on the physicochemical properties of the emulsion systems, wh ereas storage temperature and time did not. Irrespective of emulsifier type, storage temperature and time, the percentage incorporation of n aproxen in emulsions was between 80 and 100%. The degree of haemolysis induced by other emulsion components (dimethylsulfoxide (DMSO) and na proxen solution in DMSO) was about 10 times higher than that induced b y emulsion systems. Conclusion: Choice of emulsifier is the most impor tant factor in the stability of the naproxen emulsions.