Co-administration of rofecoxib and tramadol results in additive or sub-additive interaction during arthritic nociception in rat

Sigma-1 receptor antagonist (BD-1063) potentiates the antinociceptive effect of quercetin in neuropathic pain induced by chronic constriction injury

Neuropathic pain is characterized by the presence of hyperalgesia and allodynia. Pharmacological treatments include the use of antiepileptics such as pregabalin or gabapentin, as well as antidepressants; however, given the role of the sigma-1 receptor in the generation and maintenance of pain, it has been suggested that sigma-1 receptor antagonists may be effective. There are also other alternatives that have been explored, such as the use of flavonoids such as quercetin. Due to the relevance of drug combinations in therapeutics, the objective of this work was to evaluate the effect of the combination of BD-1063 with quercetin in a chronic sciatic nerve constriction model using the "Surface of Synergistic Interaction" analysis method. The combination had preferable additive or synergistic effects, with BD-1063 (17.8 mg/kg) + QUER (5.6 mg/kg) showing the best antinociceptive effects. The required doses were also lower than those used individually to obtain the same level of effect. Our results provide the first evidence that the combination of a sigma-1 receptor antagonist and the flavonoid quercetin may be useful in the treatment of nociceptive behaviors associated with neuropathic pain, suggesting a new therapeutic alternative for this type of pain.

Antinociceptive Effect of Racemic Flurbiprofen and Caffeine Co-Administration in an Arthritic Gout-Type Pain in Rats

Preclinical Research Drug combinations are routinely used in the treatment of pain. In drug associations, adjuvants such as caffeine, are employed with different non-steroidal anti-inflammatories drugs (NSAIDs), however, at present does not exist studies showing the effect of the combination of racemic flurbiprofen (rac-Flur) in association with caffeine. The objective of this work was to evaluate the combination of rac-Flur + caffeine oral in arthritic gout-type pain in rats. The antinociceptive effects of the rac-Flur alone and in combination with caffeine were analyzed on a pain-induced functional impairment model in rat. rac-Flur induced a dose-dependent antinociceptive effect and caffeine did not present any effect. The combination of rac-Flur and caffeine achieve a higher percentage of antinociceptive effect compared with the individual administration of rac-Flur. The dose-response curve (DRCs) shows that the combination of rac-Flur (31.6 mg/kg) + caffeine (17.8 mg/kg) exhibited the maximal antinociceptive efficacy (294.0 ± 21.2 area units), while rac-Flur alone (31.6 mg/kg) showed 207.2 ± 35.2 au, thus indicating an increase in efficacy (potentiation). Furthermore, the DRCs of the combinations presented a displacement to the left, indicating a change in the potency. Caffeine is able to increase the effect of rac-Flur in the arthritic gout-type pain in rats. Drug Dev Res 77 : 192-198, 2016.   © 2016 Wiley Periodicals, Inc.

Antioxidant, analgesic and anti-inflammatory effects of lavender essential oil

Several studies have investigated the antinociceptive, immunomodulatory and anti-inflammatory properties of compounds found in the lavender essential oil (LEO), however to date, there is still lack of substantial data. The objective of this study was to assess the antioxidant, anti-inflammatory and antinociceptive effects of lavender essential oil. The 1,1-diphenyl-2-picrylhydrazyl radical decolorization assay was used for antioxidant activity evaluation. The anti-inflammatory activity was tested using two models of acute inflammation: carrageenan-induced pleurisy and croton oil-induced ear edema. The antinociceptive activity was tested using the pain model induced by formalin. LEO has antioxidant activity, which is dose-dependent response. The inflammatory response evoked by carrageenan and by croton oil was reduced through the pre-treatment of animals with LEO. In the pleurisy model, the drug used as positive control, dexamethasone, was more efficacious. However, in the ear swelling, the antiedematogenic effect of the oil was similar to that observed for dexamethasone. In the formalin test, LEO consistently inhibited spontaneous nociception and presented a similar effect to that of tramadol. The results of this study reveal (in vivo) the analgesic and anti-inflammatory activities of LEO and demonstrates its important therapeutic potential.

Coadministration of tramadol and tizanidine in an experimental acute pain model in rat

Preclinical Research The use of drug combinations to achieve a desired effect is a common practice in pharmacological reaserch and in clinical practice. The present study was designed to evaluate the potential synergistic antinociceptive interactions between tizanidine, an α-2-adrenoceptor agonist and tramadol on formalin-induced nociception in rat using isobolographic analyses. Tramadol (0.1-100 μg/paw) and tizanidine (0.01-10 μg/paw) were injected into the paw prior to formalin injection (1%). Both drugs produced a dose-dependent antinociceptive effect. The EC50 values were estimated for individual drugs, and isobolograms were constructed. Tizanidine (EC50  = 0.125 ± 0.026 μg) was more potent than tramadol (EC50  = 16.45 ± 6.4 μg). The combination of tramadol-tizanidine at fixed ratios of 1:1 (EC50exp  = 67.43 ± 11 μg; EC50teo  = 8.28 ± 3.2 μg) and 3:1 (EC50exp  = 31.25 ± 9.49 μg; CE50teo  = 12.36 ± 4.8 μg) generated subadditivity (antagonism). On the basis of the current preclinical data, the pharmacological profile of the combination of tramadol-tizanidine produced antagonism. Thus, the utmost caution is required during the use of this combination in clinical practice, due to their antagonistic interaction.

The effect of tramadol and indomethacin coadministration on gastric barrier function in dogs

Background

Tramadol is a centrally acting analgesic that is often used in conjunction with nonsteroidal anti‐inflammatory drugs (NSAIDs). The effect of coadministration of tramadol and indomethacin on gastric barrier function in dogs is unknown.

Hypothesis/Objectives

That coadministration of a nonselective NSAID (indomethacin) and tramadol would decrease recovery of barrier function as compared with acid‐injured, indomethacin‐treated, and tramadol‐treated mucosa.

Animals

Gastric mucosa of 10 humanely euthanized shelter dogs.

Methods

Ex vivo study. Mounted gastric mucosa was treated with indomethacin, tramadol, or both. Gastric barrier function, prostanoid production, and cyclooxygenase expression were quantified.

Results

Indomethacin decreased recovery of transepithelial electrical resistance after injury, although neither tramadol nor the coadministration of the two had an additional effect. Indomethacin inhibited production of gastroprotective prostanoids prostaglandin E₂ (acid‐injured PGE₂: 509.3 ± 158.3 pg/mL, indomethacin + acid injury PGE₂: 182.9 ± 93.8 pg/mL, P < .001) and thromboxane B₂ (acid‐injured TXB₂: 233.2 ± 90.7 pg/mL, indomethacin + acid injury TXB₂: 37.9 ± 16.8 pg/mL, P < .001), whereas tramadol had no significant effect (PGE₂P = .713, TXB₂P = .194). Neither drug had an effect on cyclooxygenase expression (COX‐1 P = .743, COX‐2 P = .705). Acid injury induced moderate to marked epithelial cell sloughing, which was unchanged by drug administration.

Conclusions and Clinical Importance

There was no apparent interaction of tramadol and a nonselective cyclooxygenase in this ex vivo model. These results suggest that if there is an adverse interaction of the 2 drugs in vivo, it is unlikely to be via prostanoid inhibition.

Antihypernociceptive synergy between ibuprofen, paracetamol and codeine in rats

We investigated the effects of intraperitoneal injections of a combination of two cyclo-oxygenase inhibitors, ibuprofen and paracetamol, with a weak opiate, codeine, on nociception in Sprague Dawley rats. Administration of paracetamol (11, 44, and 88 mg/kg), ibuprofen (8.75, 35, and 140 mg/kg) or codeine (0.44, 1.75, and 3.5mg/kg) alone caused a dose-dependent inhibition of reperfusion hypernociception. Administration of a combination of 0.44 mg/kg codeine+8.75 mg/kg ibuprofen+11 mg/kg paracetamol, drug doses that did not significantly reduce reperfusion hypernociception when administered individually or in pairs, abolished reperfusion hypernociception, such that the antihypernociceptive efficacy of the combination was approximately 2.5-fold greater than that of the sum of the antihypernociceptive efficacy of the individual drugs. Coordinated motor function, tested using a rotarod, was not impaired at the doses we used. Thus, we have demonstrated that codeine, paracetamol and ibuprofen act synergistically to induce antihypernociception in rats at doses which do not affect motor function.

Nefopam and ketoprofen synergy in rodent models of antinociception

Combinations of analgesics with different mechanisms of action offer the possibility of efficient analgesia with a decrease in side effects as a result of reduced dosages of one or both compounds. Based on a clinical observation of synergism between nefopam, a centrally acting non-opioid that inhibits monoamines reuptake, and ketoprofen, a non-steroidal anti-inflammatory drug, the objective of this study was to further explore this antinociceptive synergy in four distinct animal models of pain (both drugs were administered subcutaneously). Strong antinociceptive properties were observed in the mouse writhing abdominal test with ED50 values of 2.56+/-0.38 and 1.41+/-0.41 mg/kg for nefopam and ketoprofen, respectively. In the inflammatory phase of the mouse formalin test, both compounds significantly inhibited the licking time of the injected hind-paw with ED50 of 4.32+/-0.17 mg/kg for nefopam and 49.56+/-15.81 mg/kg for ketoprofen. Isobolographic analysis revealed that this drug combination is synergistic in the formalin test and additive in the writhing test. In rat carrageenan-induced tactile allodynia, single administration of nefopam or ketoprofen only partially reduced allodynia. Combination of low analgesic doses of nefopam (10 or 30 mg/kg) with low analgesic doses of ketoprofen (30 or 100 mg/kg) significantly reduced or reversed allodynia, with a more pronounced anti-allodynic effect and a longer duration efficacy. In a rat model of postoperative thermal hyperalgesia induced by incision, co-administration of nefopam at a low analgesic dose (10 mg/kg) with ketoprofen at non-analgesic doses (30 or 100 mg/kg) showed the appearance of a strong anti-hyperalgesic effect, maintained during at least 3 h. In conclusion, co-administration of nefopam with ketoprofen is synergistic, and should allow either to increase their analgesic efficacy and/or to reduce their side effects.