Butorphanol, chemical name (-)-17-(cyclobutylmethyl)morphinan-3,14-diol, was reviewed by a WHO Review Group in 1981 (11) and 1983 (6), and at the twenty-fifth meeting of the Committee (7), which did not recommend international control.

Butorphanol is a synthetically derived opioid compound with mixed agonist-antagonist properties at the μ-opioid receptor. It exerts its analgesic effect by acting as an agonist at the κ-opioid receptors. Butorphanol has a profile of actions similar to those produced by pentazocine. Two to three milligrams of parenterally administered butorphanol produce analgesia and respiratory depression approximately equal to that caused by 10 mg of morphine. There have been a significant number of reports of abuse, withdrawal syndrome and dependence related to butorphanol and this drug ranks first in the list of all drugs for which drug dependence has been reported as an adverse drug reaction to the WHO International Drug Monitoring Programme. Most of these reports originated from Canada, Italy, the United Kingdom and the USA. In Canada, drug-seeking behaviour has been reported in association with the use and abuse of butorphanol nasal spray. At least four countries have taken regulatory actions to control butorphanol, indicating that its abuse is considered as a significant problem in more than one country.

Recommendation

On the basis of the above data the Committee recommended the critical review of butorphanol.