Articles: analgesics.
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(-)-N6-(R-phenylisopropyl)-adenosine (PIA) was shown to possess analgesic activity in both the tail flick and acetic acid writhing assays. The analgesic actions of PIA were antagonized by caffeine in a dose-dependent manner. An apparent pA2 analysis in vivo suggested that the antagonism by caffeine was not competitive. ⋯ PIA attenuated while caffeine exacerbated opiate withdrawal. While a low dose of caffeine antagonized PIA effects on withdrawal, a low dose of PIA did not antagonize the effects of caffeine. These results indicate that PIA can facilitate, and caffeine can antagonize the actions of morphine and that caffeine may be exerting some of its actions independent of adenosine receptor antagonism.
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Comparative Study Clinical Trial Controlled Clinical Trial
A modified cold stimulation technique for the evaluation of analgesic activity in human volunteers.
This report describes the effects of a modified cold pressure technique (MCP) on the dominant hand of 6 healthy right-handed volunteers, after single p.o. doses of codeine (60 mg), aspirin (1 g) and placebo in a cross-over, double-blind design. The method employed 9 serial tests on each study day, involving 5 consecutive 2 min periods of hand immersion in an equilibrating bath at constant temperature (37 degrees C), followed by a stimulating bath (0 degree C +/- 0.5) containing 15% ethylene glycol. ⋯ Codeine was statistically different from placebo (P less than 0.05). It is concluded that this modified technique offers a stable and sensitive method for the early assessment of analgesic activity.