BUTRUM-1

Indications

• Moderate to severe pain management
• Postoperative pain control
• Labor pain management
• Migraine treatment

Dosage

Children: Refer to the BNF for Children for appropriate dosing information in paediatric patients, ensuring age and weight considerations are addressed.

Adults: Refer to the BNF for specific dosing recommendations for adults, tailored to the individual's clinical condition and response.

Mechanism of action

The exact mechanism of action is unknown, but butorphanol is believed to interact with opiate receptor sites in the central nervous system, particularly in or associated with the limbic system. It exhibits partial agonism and partial antagonism at the μ-opioid receptor, as well as partial activity at the κ-opioid receptor, leading to its analgesic effects and a lower risk of dependence compared to full agonists.

Pharmacodynamics

Butorphanol is classified as an agonist-antagonist analgesic, which means that it can provide pain relief while also minimizing some of the side effects commonly associated with traditional opioids. Its pharmacological profile has been well established since its introduction in 1978. The transnasal formulation offers a noninvasive method for pain management and achieves systemic bioavailability similar to parenteral administration, bypassing significant first-pass metabolism seen with oral formulations. It effectively blocks pain impulses at specific sites in the brain and spinal cord.

Pharmacokinetics

Butorphanol is absorbed effectively when administered parenterally or via the nasal route, with rapid onset of action. Its distribution and elimination half-life are influenced by its formulation. The drug undergoes hepatic metabolism, primarily via the cytochrome P450 system, and is excreted in urine primarily as metabolites. Due to significant first-pass metabolism, oral bioavailability is markedly reduced compared to parenteral routes.

Contra-indications

• Hypersensitivity to butorphanol or any of its excipients
• Severe respiratory depression
• Acute or severe asthma
• Concurrent use with monoamine oxidase inhibitors (MAOIs)

Adverse effects

• Drowsiness
• Dizziness
• Nausea
• Vomiting
• Constipation
• Respiratory depression
• Sedation
• Headache

Interactions

• Other central nervous system depressants (e.g., benzodiazepines, alcohol) may enhance sedative effects
• MAOIs can increase the risk of serious side effects

Precautions

• Use with caution in patients with a history of substance abuse
• Monitor respiratory function in patients with compromised respiratory status
• Caution in elderly patients or those with hepatic or renal impairment

Pregnancy

Butorphanol should only be used in pregnancy if the potential benefit justifies the potential risk to the fetus. It is classified as a Category C drug.

Breast-feeding

Butorphanol is excreted in breast milk. Caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from light and moisture. Keep out of reach of children.

Formulations

• Injectable solution
• Intranasal spray

Mechanism of action

The exact mechanism of action is unknown, but is believed to interact with an opiate receptor site in the CNS (probably in or associated with the limbic system). The opiate antagonistic effect may result from competitive inhibition at the opiate receptor, but may also be a result of other mechanisms. Butorphanol is believed to have both partial agonism and partial antagonism at the μ-opioid receptor, as well as partial agonist and antagonist activity at the κ-opioid receptor.

Pharmacodynamics

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. Butorphanol blocks pain impulses at specific sites in the brain and spinal cord.