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A randomized, controlled trial validates a peripheral supra-additive antihyperalgesic effect of a paracetamol-ketorolac combination

Published in Basic & Clinical Pharmacology & Toxicology. 2011, vol. 109, no. 5, p. 357-64
Abstract The combination of paracetamol with non-steroidal anti-inflammatory drugs (NSAIDs) is widely used; however, the nature and mechanism of their interaction are still debated. A double-blind, pharmacokinetic/pharmacodynamic, randomized, cross-over, placebo-controlled study was carried out in human healthy volunteers. The aim was to explore the existence of a positive interaction between paracetamol 1 g and ketorolac 20 mg administered intravenously on experimental pain models in human beings. The effects of the paracetamol-ketotolac combination were compared with similar doses of respective single analgesic and to placebo on the sunburn model (UVB-induced inflammation), cold pain tolerance and the nociceptive flexion reflex. The kinetics of the plasma concentrations of paracetamol and ketorolac were measured using 2D-liquid chromatography-mass spectrometry. Thirteen volunteers were screened, and 11 completed the study. Ketorolac significantly decreased primary hyperalgesia to heat stimuli compared with paracetamol (p < 0.014). The combination performed better than paracetamol (p < 0.001) and placebo (p < 0.042), increasing heat pain threshold by 1.5°C. The combination radically reduced primary hyperalgesia to mechanical stimulation (39%) compared with placebo (p < 0.002) and single agents (paracetamol p < 0.024 and ketorolac p < 0.032). The combination also reduced, slightly although significantly, the intensity of pain (10%) for the cold pressor test (versus placebo: p < 0.012, paracetamol: p < 0.019 and ketorolac p < 0.004). None of the treatments significantly affected the central models of pain at this dosage level. No pharmacokinetic interactions were observed. These results suggest a supra-additive pharmacodynamic interaction between paracetamol and ketorolac in an inflammatory pain model. The mechanism of this interaction could mainly rely on a peripheral contribution of paracetamol to the effect of NSAIDs.
Keywords Acetaminophen/administration & dosage/pharmacokineticsAdultAnalgesics/administration & dosageAnti-Inflammatory Agents, Non-Steroidal/therapeutic useAntipyretics/administration & dosage/pharmacokineticsCross-Over StudiesDouble-Blind MethodDrug CombinationsGas Chromatography-Mass SpectrometryHumansHyperalgesia/drug therapyInflammation/drug therapyKetorolac/administration & dosage/pharmacokineticsMaleMiddle AgedPain/drug therapyRadiodermatitis/drug therapy/pathologyYoung Adult
PMID: 21615691
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Research groups Groupe Desmeules Jules (pharmacologie/toxicologie) (567)
Groupe Pierre Dayer (pharmacologie/toxicologie) (78)
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ING LORENZINI, Kuntheavy et al. A randomized, controlled trial validates a peripheral supra-additive antihyperalgesic effect of a paracetamol-ketorolac combination. In: Basic & Clinical Pharmacology & Toxicology, 2011, vol. 109, n° 5, p. 357-64. https://archive-ouverte.unige.ch/unige:43695

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Deposited on : 2014-12-17

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