Dipipanone and nifedipine in cold induced pain; analgesia not due to skin warming.

The mechanism of the pain relief produced by opiates in normal volunteers in the cold induced pain test has been investigated. In a double-blind placebo controlled study, hand skin temperature during a 3 min immersion in water at 1 degree C was not affected by either the opioid dipipanone 8 mg or the vasodilator nifedipine 10 and 20 mg. During this immersion, dipipanone produced significant pain relief. Nifedipine reduced pre-immersion blood pressures and raised heart rates, however, it did not significantly alter pain scores. It is concluded that vasodilatation and local warming do not play a role in the relief of pain by opiates in the cold immersion test.