Morphine is a naturally occurring phenanthrene alkaloid and the principal active opioid derived from the opium poppy, Papaver somniferum. It is a potent mu-opioid receptor agonist, serving as the gold standard for the relief of severe acute and chronic pain. In the Indian context, it is a critical component of palliative care and cancer pain management, though its use is strictly regulated under the Narcotic Drugs and Psychotropic Substances (NDPS) Act, 1985.
Adult: Individualized. For opioid-naïve patients: Oral (immediate-release): Start with 5-10 mg every 4 hours as needed. Parenteral (IM/SC): 2.5-5 mg every 4 hours. IV: 1-2 mg slow IV push, titrated. For chronic pain, use controlled-release formulations (e.g., 10-30 mg every 12 hours) after establishing dose with immediate-release.
Note: Oral: Can be taken with or without food. Do not crush, chew, or break controlled-release tablets (e.g., Morphine SR). Parenteral: Administer IM/SC/IV. For IV, inject slowly over 4-5 minutes to avoid severe respiratory depression. Rotate SC injection sites. Always initiate therapy at the lowest possible dose and titrate to effect.
Morphine exerts its analgesic and euphoric effects primarily by binding to and activating mu-opioid receptors (MOR) in the central nervous system (CNS) and peripheral nervous system. This agonist action mimics endogenous opioids (endorphins).
Pregnancy: Pregnancy Category C (US FDA). Chronic use can lead to neonatal opioid withdrawal syndrome (NOWS) if used near term. Use during labor can cause neonatal respiratory depression. Use only if potential benefit justifies potential fetal risk. Avoid during first trimester unless absolutely necessary.
Driving: Morphine impairs mental and/or physical abilities required for driving or operating machinery. Patients must be warned not to drive or engage in hazardous activities until they know how the drug affects them, especially during initiation and dose titration. Drowsiness and dizziness are common.
| Other CNS Depressants (Benzodiazepines, Alcohol, Barbiturates, Sedative-hypnotics) | Additive CNS and respiratory depression, profound sedation, coma, death. | Major |
| MAO Inhibitors (Phenelzine, Tranylcypromine) | Exaggerated opioid effects, serotonin syndrome, hyperpyrexia, coma. | Contraindicated |
| Mixed Agonist-Antagonists (Pentazocine, Nalbuphine, Butorphanol) | May precipitate withdrawal in opioid-dependent patients and reduce analgesia. | Major |
| Anticholinergics (Atropine, Tricyclic Antidepressants) | Increased risk of severe constipation, urinary retention, paralytic ileus. | Moderate |
| Rifampicin | Induces UGT enzymes, increasing morphine metabolism and reducing efficacy. | Moderate |
| CYP3A4 Inhibitors (Ketoconazole, Clarithromycin, Ritonavir) | May inhibit minor metabolic pathways, potentially increasing morphine levels. | Moderate |
| Diuretics | Morphine-induced release of antidiuretic hormone may reduce efficacy of diuretics. | Moderate |
| Muscle Relaxants | Enhanced neuromuscular blocking action. | Moderate |
Same composition (Morphine (10mg)), different brands: