Butorphanol and nalbuphine: a pharmacologic comparison.

The agonist/antagonist analgesics, butorphanol (Stadol) and nalbuphine (Nubain), are being increasingly employed as intravenous sedation agents; nalbuphine will be available in the future as an oral analgesic. The drugs possess numerous pharmacologic similarities and some dissimilarities. Both are equianalgesic (and nalbuphine is equipotent) with morphine parenterally and codeine orally. Their pharmacokinetics are similar; nalbuphine has a longer duration of action. Both may precipitate an abstinence syndrome in narcotic-dependent persons and will probably be associated with low-level drug abuse potential. They are both agonists of the kappa opioid receptor and partial agonists of the mu receptor. Butorphanol is a partial agonist of the sigma receptor responsible for psychotomimetic effects. The incidence of adverse effects is low, sedation being the most common. In cardiac-risk patients, nalbuphine does not increase cardiac work or oxygen requirements; nor do increasing doses of nalbuphine increase the duration of respiratory depression. Both drugs possess plateau respiratory depressant actions.