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This study was designed to evaluate the antinociceptive interaction of the tramadol-meloxicam combination in different proportions (tramadol 1 meloxicam in 1:1, 1:3, and 3:1 ratios), as well as the role of nitric oxide, opioidergic, and serotonergic pathways in the antinociceptive effect of the combination. The effects of individual drugs and fixed-ratio combinations were assayed using the 3% formalin test in mice. Isobolographic analysis was employed to characterize the synergism produced by the combinations. Tramadol (3.16-10 mg/kg, i.m.), meloxicam (3.16-17.8 mg/kg, i.m.), and tramadolmeloxicam combinations produced a dose-dependent antinociceptive effect. ED 30 values were estimated for the individual drugs, and isobolograms were constructed. The tramadol 1 meloxicam 1:1 and 1:3 ratio combinations showed synergistic interactions while the 3:1 ratio produced additive effects. Naloxone (1 mg/kg, i.m.) or methiothepin (0.1 mg/kg, i.m.), but not L-NAME (3 mg/kg, i.m.), prevented the antinociceptive effects of the combination. These data suggest that (1) the tramadol-meloxicam combination produces a functional synergistic interaction that involves both opioid and serotonin receptors, and (2) this combination may be a promising tool in pain management. Drug Dev Res, 2011.

There is evidence that B vitamins produce antinociception in animals. However, potentiation of NSAID-induced antinociception by B vitamins is unclear. The current study was designed to investigate the antinociceptive interaction between a mixture of B vitamins and either acetaminophen or metamizol. Acetaminophen (56-316 mg/kg), metamizol (32-178 mg/kg), and the mixture of B vitamins (32-178 mg/kg of thiamine, pyridoxine, and cyanocobalamin in a 100:100:1 proportion, respectively) or a combination of each drug with the B vitamins mixture was administered orally to female Wistar rats, and the antinociceptive effect determined in the formalin test. Isobolographic analyses were used to define the nature of the interaction between NSAIDs and B vitamins. Oral administration of either drug produced a dose-related antinociceptive effect. Isobolographic analyses revealed that both acetaminophen or metamizol and the B vitamins mixture interacted synergistically in the formalin test, suggesting that these two combinations could be useful in treating inflammatory pain states. Drug Dev. Res. 66:286-294, 2006.

The aim of this in vitro study was to evaluate the interaction between ciprofloxacin and amoxicillin against beta-lactamase-producing Staphylococcus aureus. Concentration-dependent curves for each individual drug were carried out to obtain the mean inhibitory concentration in the agar well diffusion assay. Then, different ratios of the ciprofloxacin-amoxicillin combination (0.