Morphine is a naturally occurring phenanthrene alkaloid and the principal active opioid in opium. It is a potent mu-opioid receptor agonist, primarily used for the management of severe, acute, and chronic pain, particularly in palliative care and cancer pain. In the Indian context, it is a critical component of the WHO analgesic ladder for moderate to severe pain and is subject to strict narcotic control regulations under the NDPS Act.
Adult: Individualized. For opioid-naïve patients: Oral: Start with 5-15 mg every 4 hours as needed. For severe chronic pain, use around-the-clock dosing. Conversion from other opioids is necessary. 30mg tablet is typically for patients already stabilized on morphine therapy.
Note: Tablet: Swallow whole with water. Can be taken with or without food, but consistency reduces variability. Do not crush, chew, or break sustained-release formulations. For immediate-release, administer every 4 hours as needed for pain. Always initiate therapy at the lowest effective dose.
Morphine exerts its primary analgesic effect 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). Activation of G-protein coupled mu-receptors inhibits adenylate cyclase, reduces intracellular cAMP, and leads to hyperpolarization of neurons by opening potassium channels and inhibiting voltage-gated calcium channels. This suppresses the release of excitatory neurotransmitters (e.g., substance P, glutamate) and reduces neuronal excitability.
Pregnancy: Pregnancy Category C (US FDA). Chronic use during pregnancy can lead to neonatal opioid withdrawal syndrome (NOWS) which may be life-threatening. Use during labor can cause neonatal respiratory depression. Use only if potential benefit justifies potential fetal risk.
Driving: IMPAIRED ABILITY. Causes drowsiness, dizziness, sedation, and impaired judgment. Patients must not drive or operate machinery until effect is known.
| Other CNS Depressants (Alcohol, Benzodiazepines, Barbiturates, Sedative-hypnotics) | Additive CNS and respiratory depression, profound sedation, coma, death. | Major |
| MAO Inhibitors (Phenelzine, Tranylcypromine, Linezolid) | Risk of serotonin syndrome, excitatory reactions (hyperpyrexia, rigidity). | Contraindicated |
| Mixed Agonist/Antagonists & Partial Agonists (Pentazocine, Nalbuphine, Buprenorphine) | May precipitate withdrawal in opioid-dependent patients and reduce analgesic effect. | Major |
| Opioid Antagonists (Naloxone, Naltrexone) | Precipitates acute withdrawal and reverses analgesia. | Major |
| Anticholinergics (Atropine, Tricyclic Antidepressants) | Increased risk of urinary retention, severe constipation, paralytic ileus. | Moderate |
| Diuretics | Morphine-induced release of ADH may reduce diuretic efficacy. | Moderate |
| CYP3A4 Inhibitors (Ketoconazole, Erythromycin, Ritonavir) | May increase morphine levels (minor pathway). | Moderate |
| CYP3A4 Inducers (Rifampicin, Carbamazepine, Phenytoin) | May decrease morphine levels. | Moderate |
| Serotonergic Drugs (SSRIs, SNRIs, TCAs, Tramadol) | Increased risk of serotonin syndrome. | Major |
Same composition (Morphine (30mg)), different brands: