Aim: The purpose of this study was to determine the antinociceptive activity of paracetamol and ibuprofen, and the degree of interaction between them, using the isobolographic analysis in the formalin orofacial test in mice
Materials and methods: About 200 male mice of the strain CF / 1 (Mus musculus) were used, The study was conducted according to protocol FMUCH CBA No. 238, approved by the Ethics Committee of the Faculty of Medicine of the University of Chile.
The injected doses used were 3, 10, 30, 100 mg / kg for ibuprofen and 30, 50, 100 and 200 mg / kg for paracetamol. In the control animals i.p. saline were injected. This generates a pain response that is recorded in two phases of behavior: an initial, during the five minutes immediately following the injection of formalin (phase I) and a late phase of 10 minutes, measured at 20 minutes after administration of formalin solution (phase II).
Then the efective dose (ED) 50 and ED 25 were obtain of both drugs and injected together.
To evaluate the analgesic interaction between ibuprofen and acetaminophen combination, we used the method of analysis isobolografic from the Neuropharmacology Laboratory, adapted from Tallarida.
Results
Results: The results obtained show that administration of ibuprofen and paracetamol produced a dose-dependent antinociceptive activity in both phases of the test of orofacial formalin and the used of both together results in a synergistic interaction. Conclusion: In conclusion, the synergism of the paracetamol and ibuprofen may improve this type of therapeutic profile, since with low doses of the components, side effects are not likely to occur, and they may be used in long-term treatments.