Interactions of aspirin and salicylic acid with prednisolone for inhibition of lymphocyte proliferation.

The anti-inflammatory properties of salicylates and prednisolone were investigated using inhibition of in vitro phytohemagglutinin-stimulated lymphocyte proliferation in human whole blood from healthy male and female subjects. Steroids and salicylates are used in conjunction for the treatment of inflammatory disorders such as rheumatoid arthritis and inhibit the proinflammatory transcription factor, NFKB, by different mechanisms. Data generated using various combinations of these drugs were analyzed using isobolograms and the universal surface response approach based on the Loewe additivity principle. The interaction between aspirin and prednisolone was mildly antagonistic while that between salicylic acid and prednisolone was modestly synergistic at therapeutic concentrations. Further, aspirin was slightly more potent in males, but the nature of the steroid-salicylate interaction was similar across genders. This study helps rationalize part of the beneficial effects of steroids and salicylates in treatment of inflammatory disorders.