Medicament Release from Suppository Bases: II. Naproxen Physicochemical Characteristics and Bioavailability in Rabbits

Suppositories containing 25mg naproxen were prepared by the fusion method with tehobroma oil, PEG 1000, and witepsol 11-15. The liguefaction point and the time for complete liquefaction at temperatures from 37°C to 47°C were determined. By utilizing the SBT (Erwka) apparatus it was determined that the witepsol 11-15 formed supposltories which were more brittle.The In vitro release rates were determined by using the USP method and by a modified one with dialyzing cellophane tubing. Samples withdrawn at definite time interval for up to 6 hours, and were analyzed by the spectrofluorometric method. The in vivo drug release was studied in rabbits. Ten blood samples were collected over a 24 hour period following administration of a 25mg dose of each suppository and of oral suspension. Plasma samples were assayed by spectrofluorometric method. A student “t” test was conducted on all date from the four different formulations and indicated significant difference between theobroma oil and oral suspension.Significant correlation was obtained between the in vivo absorption and in vitro release when the suppository was placed In a dialyzing cellophane membrane.