Proglumide enhances the antinociceptive effect of cyclooxygenase inhibitors in diabetic rats in the formalin test

Combination of diacerhein and antiepileptic drugs after local peripheral, and oral administration in the rat formalin test

Preclinical Research The present study was designed to evaluate the possible antinociceptive interaction between diacerhein and some antiepileptic drugs (carbamazepine, topiramate and gabapentin) on formalin-induced nociception. Diacerhein, each of the antiepileptics or a fixed dose-ratio combination of these drugs was assessed after local peripheral and oral administration in rats. lsobolographic analyses were used to define the interaction between drugs. Diacerhein, antiepileptic drugs (carbamazepine, topiramate and gabapentin) or their combinations yielded a dose-dependent antinociceptive effect when administered by both routes. Theoretical ED30 values for the combination estimated from the isobolograms were obtained as follows: diacerhein-carbamazepine (85.99 ± 7.07 μg/paw; 56.53 ± 4.56 mg/kg po), diacerhein-topiramate (197.97 ± 22.90 μg/paw; 13.06 ± 2.44 mg/kg po) and diacerhein-gabapentin (96.87 ± 17.73 μg/paw; 17.90 ± 4.70 mg/kg p.o.) for the local peripheral and oral administration routes, respectively. These values were significantly higher than the experimentally obtained ED30 values: diacerhein-carbamazepine (49.33 ± 3.37 μg/paw; 35.49 ± 7.91 mg/kg po), diacerhein-topiramate (133.00 ± 39.10 μg/paw; 8.87 ± 1.46 mg/kg po) and diacerhein-gabapentin (70.98 ± 14.73 μg/paw; 10.95 ± 3.23 mg/kg po). The combinations produced their antinociceptive effects without motor impairment in the rotarod test indicating synergistic interactions with a good side effect profile.

Role of ATP-sensitive K+ channels in the antinociception induced by non-steroidal anti-inflammatory drugs in streptozotocin-diabetic and non-diabetic rats

There is evidence that systemic sulfonylureas block diclofenac-induced antinociception in normal rat, suggesting that diclofenac activates ATP-sensitive K(+) channels. However, there is no evidence for the systemic interaction between different non-steroidal anti-inflammatory drugs (NSAIDs) and sulfonylureas in streptozotocin (STZ)-diabetic rats. Therefore, this work was undertaken to determine whether two sulfonylureas, glibenclamide and glipizide, have any effect on the systemic antinociception that is induced by diclofenac (30 mg/kg), lumiracoxib (56 mg/kg), meloxicam (30 mg/kg), metamizol (56 mg/kg) and indomethacin (30 mg/kg) using the non-diabetic and STZ-diabetic rat formalin test. Systemic injections of NSAIDs produced dose-dependent antinociception during the second phase of the test in both non-diabetic and STZ-diabetic rats. Systemic pretreatment with glibenclamide (10 mg/kg) and glipizide (10 mg/kg) blocked diclofenac-induced systemic antinociception in the second phase of the test (P<0.05) in both non-diabetic and STZ-diabetic rats. In contrast, pretreatment with glibenclamide or glipizide did not block lumiracoxib-, meloxicam-, metamizol-, and indomethacin-induced systemic antinociception (P>0.05) in both groups. Results showed that systemic NSAIDs are able to produce antinociception in STZ-diabetic rats. Likewise, data suggest that diclofenac, but not other NSAIDs, activated K(+) channels to induce its systemic antinociceptive effect in the non-diabetic and STZ-diabetic rat formalin test.