NALOXONE BLOCKADE OF MORPHINE ANALGESIA - DOSE-EFFECT STUDY OF DURATION AND MAGNITUDE

  • 1 January 1976
    • journal article
    • research article
    • Vol. 199  (2) , 385-388
Abstract
The minimal dose of naloxone needed to block the analgesic effect of morphine as measured by the foot-shock titration procedure in the rat was determined. Various groups of rats received, s.c., various doses of naloxone hydrochloride, from 0.03-2.0 mg/kg, 15 min before receiving 10 mg/kg of morphine sulfate. Naloxone 1.0 mg/kg is the minimum dose necessary to provide full blockade of the measured morphine effect for up to 5 h after morphine administration. Partial blockade was evident at doses much smaller than 1.0 mg/kg of naloxone. A dose of 0.125 mg/kg of naloxone completely blocked the onset of a measurable effect from 10 mg/kg of morphine for 60 min in 6 out of the 7 animals tested at that dose. A clear dose-effect relationship is provided for both magnitude and duration of naloxone blockade of the analgesic effect of morphine.

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