PHARMACOLOGY OF BUTORPHANOL, A 3,14-DIHYDROXYMORPHINAN NARCOTIC-ANTAGONIST ANALGESIC

Abstract

Butorphanol, a new, totally synthetic morphinan chemically related to naloxone, has analgesic and narcotic antagonist properties. In rodent antiwrithing analgesic tests, butorphanol was 4-30 times more potent than morphine and dl-pentazocine, respectively. As an antagonist, butorphanol was about equivalent to nalorphine and 30 times more potent than dl-pentazocine. On the basis of the naloxone-induced mouse jumping test and the lack of substitution in withdrawn morphine-dependent mice, the potential for physical dependence of butorphanol will probably be less than that of dl-pentazocine but greater than that of nalorphine and dl-cyclazocine. Agonistic actions of butorphanol, such as respiratory depression and miosis, reach ceiling effects which are lower than those seen with morphine with an increase in dosage. Butorphanol differed from morphine which exhibited agonist effects in a dose-related manner. Butorphanol showed weak to moderate central depressant properties at doses which were considerably higher (> 100.times.) than those producing analgesia. Minimal cardiovascular and respiratory effects were seen with butorphanol in conscious dogs.