1. Clinical Overview
Butorphanol tartrate is a synthetic opioid agonist-antagonist analgesic of the phenanthrene series. It is a potent analgesic with mixed agonist and antagonist actions at opioid receptors. In the Indian market, it is primarily available as an injectable formulation (IV/IM) and is used for the management of moderate to severe pain, including postoperative pain and migraine. It is also used as a pre-anesthetic medication and for balanced anesthesia. Its unique pharmacological profile offers analgesia with a potentially lower risk of respiratory depression and abuse liability compared to pure mu-opioid agonists like morphine, though it is still a scheduled drug.
| Onset | Duration | Bioavailability |
|---|---|---|
| Intravenous (IV): 2-3 minutes; Intramuscular (IM): Within 10-15 minutes. | IV: 2-4 hours; IM: 3-4 hours. | Intranasal: 60-70%; Intramuscular: ~100%. |
2. Mechanism of Action
Butorphanol is a mixed agonist-antagonist with high affinity for kappa-opioid receptors (agonist) and low affinity for mu-opioid receptors (partial agonist/antagonist). Its primary analgesic effect is mediated through agonist activity at kappa-opioid receptors in the central nervous system (CNS). Its partial agonist/antagonist activity at mu-receptors contributes to analgesia but also limits its abuse potential and respiratory depressant effects compared to full mu-agonists.
3. Indications & Uses
- Management of moderate to severe acute pain (e.g., postoperative pain, trauma, renal colic)
- Relief of pain associated with migraine headaches (commonly used in emergency settings in India)
- Pre-operative or pre-anesthetic medication
- As an adjunct for balanced general anesthesia
4. Dosage & Administration
Adult Dosage: Pain Management (IM/IV): Initial dose 1-2 mg (0.5-1 mL of 2mg/mL solution) every 3-4 hours as needed. For severe pain, 2 mg IV may be given. Pre-operative: 2 mg IM, 60-90 minutes before surgery. Migraine: 1-2 mg IV or IM.
Administration: For IV use: Administer undiluted or diluted in 5 mL of Sterile Water for Injection or Normal Saline. Inject slowly over 3-5 minutes to minimize adverse effects. For IM use: Inject deep into a large muscle mass (gluteus, deltoid, thigh). Rotate injection sites. Do not administer subcutaneously (risk of tissue irritation). The solution is clear and colorless; discard if discolored or contains particulate matter.
5. Side Effects
Common side effects may include:
- Sedation, drowsiness, dizziness
- Nausea, vomiting
- Sweating (diaphoresis)
- Feeling of floating or dissociation
- Headache
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other CNS Depressants (Alcohol, Benzodiazepines, Sedatives) | Additive CNS depression, profound sedation, respiratory depression, coma, death. | Major |
| Monoamine Oxidase Inhibitors (MAOIs) e.g., Phenelzine, Selegiline | Potentially fatal serotonin syndrome or exaggerated opioid effects (excitation, hypertension, hyperpyrexia). Contraindicated within 14 days of MAOI use. | Major |
| Pure Mu-Opioid Agonists (Morphine, Fentanyl, Methadone) | Butorphanol may antagonize the analgesic effect and precipitate acute withdrawal in physically dependent patients. | Major |
| CYP3A4 Inhibitors (Ketoconazole, Itraconazole, Clarithromycin, Ritonavir) | Increased plasma levels of butorphanol, leading to enhanced and prolonged effects/toxicity. | Moderate |
| CYP3A4 Inducers (Rifampicin, Carbamazepine, Phenytoin) | Decreased plasma levels of butorphanol, leading to reduced efficacy. | Moderate |
| Anticholinergics (Atropine, Antihistamines) | Increased risk of urinary retention, severe constipation, paralytic ileus. | Moderate |
| Diuretics (Furosemide) | Butorphanol may reduce efficacy of diuretics by inducing antidiuretic hormone release. | Moderate |
7. Patient Counselling
- DO inform your doctor about all medications, supplements, and herbal products you are taking.
- DO report any history of substance abuse, depression, or mental illness.
- DO NOT consume alcohol or sleep-inducing medications while on butorphanol.
- DO NOT drive or operate machinery until you know how the medicine affects you.
- DO inform your doctor if you are pregnant, planning pregnancy, or breastfeeding.
- DO use the medicine exactly as prescribed; do not increase the dose or frequency.
8. Toxicology & Storage
Overdose: Manifestations are an extension of its pharmacological effects: Profound respiratory depression (slow, shallow breathing, cyanosis, apnea), extreme somnolence progressing to stupor or coma, skeletal muscle flaccidity, cold and clammy skin, bradycardia, hypotension, and cardiac arrest. Pulmonary edema and death may occur.
Storage: Store at controlled room temperature (15°C to 30°C). Protect from light. Do not freeze. Keep the ampoule/vial in the outer carton. Keep out of reach and sight of children. Discard any unused portion of the opened vial/ampoule appropriately as per hospital/institutional guidelines for controlled substances. Do not use if the solution is discolored or contains particles.