Effects of α adrenergic blocking agents on narcotic induced analgesia

T. J. Cicero

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15 Scopus citations


The influence of a reduction in the action of catecholamines in the nervous system, either by a selective reduction in norepinephrine levels by inhibition of dopamine β hydroxylase or by administration of agents which block catecholamine actions at the receptor site, on morphine induced analgesia was assessed in the rat. Findings indicate that a reduction of norepinephrine in whole brain produces a marked increase in both degree and duration of analgesic response to morphine. The data also suggest that the critical factor in this effect may well be a selective reduction in the effect of norepinephrine at α adrenergic receptors since only the α adrenergic blocker, phenoxybenzamine, but not the β antagonist, propranolol, potentiated morphine induced analgesia. In addition, phenoxybenzamine, but not propranolol, markedly increased the respiratory depressant effect of morphine leading to a substantial number of deaths at doses of each drug several orders of magnitude lower than their individual LD50's.

Original languageEnglish
Pages (from-to)5-13
Number of pages9
JournalArchives Internationales de Pharmacodynamie et de Therapie
Issue number1
StatePublished - Dec 1 1974


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