[Influence of adrenergic-blocking agents on the pain-alleviating effect of narcotic analgesics]

The action of adrenoblocking agents on the dynamics of the pain allaying effect of narcotic analgesics, measured by the magnitude of the pain reaction threshold after irritation of the tail skin with electric current was studies in tests on mice. The beta-adreno-blocking agent (anaprillin or inderal) was found to significantly potentiate and to lengthen the action of morphine, and so did, to a lesser degree, promedol (trimeperedin) and phentanyl, while the alpha-adrenoblocking agent (phentolamine) weakened the analgesic effects of morphine and promedol, without having any essential influence on the effect of phentanyl. Phentolamine does not eliminate the potentiating effect of anapraline on the analgesic action of morphine but is capable to lessen it.