Antipyretic testing of commercial aspirin formulations in rats

Four commercial aspirin formulations and aspirin powder USP were assayed in yeast-fevered rats for antipyretic activity. Tablets allowed to disintegrate spontaneously prior to dosing yielded aggregates of various sizes which failed to produce uniform patterns of antipyresis. When tested at smaller, more uniform particle sizes of total product, consistent, statistically significant antipyresis was observed with no significant variation among formulations. The ED50 values and parallel line assays were homogeneous.