Butorphanol

General adverse effects and adverse reactions

In some patients, effective doses cause troublesome effects. For example, in a randomized study of patients with sickle-cell crisis who received either butorphanol 2 mg intramuscularly or morphine 6 mg intramuscularly, adverse effects occurred in 23 and 13% respectively [ ]. On the other hand, a wide range of doses (4–48 mg/day) over 1 month failed to produce scores indicative of euphoric effects, and the withdrawal syndrome resembled a cyclazocine rather than a morphine abstinence effect [ ].

Observational studies

Butorphanol is a partial agonist at MOR opioid receptors and an agonist at KOR receptors. Intranasal butorphanol has been used to treat five patients with intractable pruritus due to inflammatory skin disease or systemic disease [ ]. All had marked improvement, but one had severe nausea and withdrew. No other adverse effects were reported.

The actions of butorphanol alone and in combination with naltrexone have been explored in 10 healthy volunteers with a history of opioid abuse [ ]. They participated in experimental tests of varying doses of oral naltrexone (0, 1, 3, 10, or 30 mg) given 60 minutes before varying doses of intramuscular butorphanol (0, 6, or 12 mg/70 kg). Butorphanol alone produced predominant MOR receptor effects (e.g. miosis and respiratory depression) and changes in mood. In combination with naltrexone, it produced a significant diuresis, suggesting the unmasking of KOR receptor activity. One volunteer developed agitation , tonic–clonic seizures, and disorientation after administration of butorphanol.