Butorphanol Information

Butorphanol is a mixed agonist-antagonist with low intrinsic activity at receptors of the µ-opioid type (morphine-like). It is also an agonist at k-opioid receptors.

Its interactions with these receptors in the central nervous system apparently mediate most of its pharmacologic effects, including analgesia.

In addition to analgesia, CNS effects include depression of spontaneous respiratory activity and cough, stimulation of the emetic center, miosis and sedation. Effects possibly mediated by non-CNS mechanisms include alteration in cardiovascular resistance and capacitance, bronchomotor tone, gastrointestinal secretory and motor activity and bladder sphincter activity.

In an animal model, the dose of Butorphanol tartrate required to antagonize morphine analgesia by 50% was similar to that for nalorphine, less than that for pentazocine and more than that for naloxone.

The pharmacological activity of Butorphanol metabolites has not been studied in humans; in animal studies, Butorphanol metabolites have demonstrated some analgesic activity.