Comparison of analgesic effects of nimesulide, paracetamol, and their combination in animal models

Objectives: To compare the analgesic activity of nimesulide and paracetamol alone and their combination in animal models for the degree of analgesia and the time course of action.
Materials and Methods: Analgesia was studied in albino rats using formalin test and in albino mice using writhing test and the radiant heat method. For each test, four groups of six animals each were orally fed with a single dose of nimesulide, paracetamol, and combination of nimesulide + paracetamol and gum acacia as control, respectively.
Results: In all the three test models, all three drug treatments showed significant analgesia (P < 0.001) as compared to control, but there was no significant difference in the analgesia produced by either drugs alone or in combination. The radiant heat method demonstrated a quicker onset and longer duration of action with nimesulide, whereas writhing test showed a quicker onset of action with paracetamol. In formalin test, greater degree of analgesia was seen with individual drugs than that of the combination, though this difference was not statistically significant.
Conclusions: Nimesulide and paracetamol combination offers no advantage over nimesulide alone or paracetamol alone, either in terms of degree of analgesia or onset of action. Therefore, our study supports the reports claiming irrationality of the fixed dose combination of nimesulide and paracetamol.