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Updated: Aug 11, 2026

A Modified Inflammatory Pain Model to Study the Analgesic Effect in Mice
Published on: November 15, 2024
Synergism between paracetamol and nonsteroidal anti-inflammatory drugs in experimental acute pain
Hugo F Miranda1, Margarita M Puig, Juan Carlos Prieto
1Pharmacology Program, ICBM, Faculty of Medicine, University of Chile, Clasificador 70.000, Santiago 7, Chile. hmiranda@med.uchile.cl
Abstract:
The antinociception induced by the intraperitoneal coadministration of combinations of paracetamol with the nonsteroidal anti-inflammatory drugs (NSAIDs) diclofenac, ibuprofen, ketoprofen, meloxicam, metamizol, naproxen, nimesulide, parecoxib and piroxicam was studied by isobolographic analysis in the acetic acid abdominal constriction test of mice (writhing test). The effective dose that produced 50% antinociception (ED50) was calculated from the log dose-response curves of fixed ratio combinations of paracetamol with each NSAID. By isobolographic analysis, this ED50 was compared to the theoretical additive ED50 calculated from the ED(50) of paracetamol and of each NSAID alone obtained from ED50 dose-response curves. As shown by isobolographic analysis, all the combinations were synergistic, the experimental ED50s being significantly smaller than the theoretically calculated ED50s. The results of this study demonstrate potent interactions between paracetamol and NSAIDs and validate the clinical use of combinations of these drugs in the treatment of pain conditions.
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