1. Clinical Overview
Nalbuphine hydrochloride is a semi-synthetic opioid agonist-antagonist analgesic of the phenanthrene series. It is a potent analgesic with a potency approximately equal to morphine on a milligram basis. It is used for the relief of moderate to severe pain. In the Indian context, it is a valuable option for post-operative pain, trauma, and cancer pain, offering a ceiling effect on respiratory depression which provides a wider safety margin compared to pure mu-opioid agonists.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 2-3 minutes after IV administration; 15 minutes after IM/SC administration. | 3-6 hours. | High but variable: Intramuscular/Subcutaneous ~80-100%; Oral bioavailability is low (<20%) due to extensive first-pass metabolism, hence not used orally. |
2. Mechanism of Action
Nalbuphine binds with high affinity to kappa-opioid receptors (agonist) and with lower affinity to mu-opioid receptors (partial antagonist). Its analgesic effect is primarily mediated through agonist activity at kappa receptors in the brain and spinal cord. The antagonistic activity at mu receptors limits its euphoric effects, abuse potential, and provides a ceiling on respiratory depression.
3. Indications & Uses
- Moderate to severe acute pain (e.g., post-operative pain, trauma, renal colic)
- Pain associated with myocardial infarction
- Supplement to balanced anesthesia
- Obstetric analgesia during labor
4. Dosage & Administration
Adult Dosage: Usual dose: 10 mg (1 ml of 10 mg/ml solution) administered IV, IM, or SC every 3-6 hours as needed for pain. For severe pain, a dose of 20 mg may be required. Single doses should not exceed 20 mg. Total daily dose should not exceed 160 mg.
Administration: Can be administered undiluted by slow IV injection over 2-3 minutes. For IM/SC, inject into a large muscle mass or subcutaneous tissue. Rotate injection sites. Do not mix in same syringe with other drugs unless compatibility is known. Aspirate before injection to avoid intravascular administration.
5. Side Effects
Common side effects may include:
- Sedation/Drowsiness (36%)
- Sweating/Clamminess (9%)
- Nausea/Vomiting (6%)
- Dizziness/Vertigo (5%)
- Dry mouth
- Headache
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other CNS Depressants (e.g., Alcohol, Benzodiazepines, Barbiturates, Sedative Antihistamines) | Additive CNS depression, profound sedation, respiratory depression, hypotension, coma, or death. | Major |
| Pure Mu-Opioid Agonists (e.g., Morphine, Fentanyl, Pethidine) | Nalbuphine may antagonize the analgesic and respiratory depressant effects of pure agonists. May precipitate withdrawal in physically dependent patients. | Major |
| Monoamine Oxidase Inhibitors (MAOIs) e.g., Phenelzine, Selegiline | Risk of serotonin syndrome or exaggerated opioid effects (coma, severe respiratory depression). | Major |
| Mixed Agonist-Antagonists (e.g., Pentazocine, Butorphanol) | May reduce analgesic effect of nalbuphine and/or precipitate withdrawal symptoms. | Moderate |
| Anticholinergic Drugs | Increased risk of urinary retention and severe constipation. | Moderate |
7. Patient Counselling
- DO take exactly as prescribed by the doctor.
- DO inform all your doctors and dentists that you are taking this medicine.
- DO NOT crush, break, or chew the injection vial.
- DO NOT suddenly stop the medication after prolonged use; taper under doctor's guidance.
- DO NOT share your medicine with anyone else.
- DO keep medicine out of reach of children and pets.
8. Toxicology & Storage
Overdose: Triad of opioid overdose: 1) Respiratory depression (may have ceiling), 2) Extreme somnolence progressing to stupor or coma, 3) Miosis (pinpoint pupils). Other symptoms: Cold/clammy skin, bradycardia, hypotension, skeletal muscle flaccidity, circulatory collapse, cardiac arrest.
Storage: Store at controlled room temperature (15°C to 30°C). Protect from light. Do not freeze. Keep in the original carton until use. Discard any unused portion from an opened vial. Keep locked up and away from unauthorized use, especially children. Dispose of unused medication as per pharmacy guidelines.