Transnasal butorphanol. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in acute pain management.

Butorphanol is a synthetic opioid agonist-antagonist analgesic with a pharmacological and therapeutic profile that has been well established since its launch as a parenteral formulation in 1978. The introduction of a transnasal formulation of butorphanol represents a new and noninvasive presentation of an analgesic for moderate to severe pain. This route of administration bypasses the gastrointestinal tract, and this is an advantage for a drug such as butorphanol that undergoes significant first-pass metabolism after oral administration. The onset of action and systemic bioavailability of butorphanol following transnasal delivery are similar to those after parenteral administration. The analgesic efficacy of transnasal butorphanol was generally superior to that of placebo in clinical trials in patients with moderate to severe postoperative pain or migraine headache. Results from single trials indicate that transnasal butorphanol provides pain relief comparable to that of intramuscular pethidine (meperidine) in postsurgical pain and comparable to or greater than intramuscular methadone in migraine headache. Moderate to severe musculoskeletal pain also appears to be responsive to transnasal butorphanol on the basis of results from 1 small noncomparative study. Tolerability of transnasal butorphanol parallels that of the injectable form, with somnolence, dizziness, nausea and/or vomiting reported most frequently. Thus, transnasal butorphanol is a novel formulation of an established analgesic which appears suitable for the short term treatment of moderate to severe pain, especially in an ambulatory setting. Transnasal butorphanol is likely to provide an alternative to oral opioid analgesics, particularly in the presence of nausea or vomiting, or to parenteral opioids when the oral route of administration is not appropriate.