The effect of ketamine, diclofenac and their combination on four models of induced pain in mice

Abstract EN

Adjuvant analgesics are drugs that have weak or nonexistent analgesic action when administered alone, but can enhance analgesic action when co-administered with known analgesic agents.

Ketamine, an anesthetic drug, is an adjuvant analgesic drug.

Its use in doses lower than therapeutic doses might be important in the management of certain types of pain as neuropathic pain.

The present study was performed to investigate the effects of sub anesthetic doses of ketamine in four animal models of induced pain and to compare its effects with diclofenac sodium.

It is also intended to test the effectiveness of combining both drugs together in these animal models of pain.

All experiments were performed on albino mice.

Mice were evaluated for their responsiveness to noxious stimuli using four tests : tail-flick test, hot-plate test, formalin test and acetic acid induced writhing test.

These effects were measured before and one hour after intraperitoneal drug administration.

In some experiments, they were followed for 6 and 24 hours.

We found that Ketamine, in sub anesthetic doses, resulted in a significant analgesic effect in all the four models of pain.

It increased pain latencies in tail-flick test by 78% compared to preadministration time, and by 95% in hot plate test.

It also decreased the number of lickings and biting in formalin test by 41.9% and the number of abdominal writhing by 73.5%.

These analgesic effects represented around 60% of diclofenac effect in heat-induced pain models, but it is similar to diclofenac in the other two models.

The enhancement of diclofenac analgesic effect by ketamine ranged from 13.6% to 46% in the four tests.

It is concluded that Ketamine in sub anesthetic doses has a significant analgesic effect comparable to diclofenac.

It can enhance diclofenac effect by a margin not exceeding 50% of diclofenac effect.

Much smaller doses of ketamine are required to be tested in the future.