Melatonin is an endogenous neurohormone primarily secreted by the pineal gland in a circadian rhythm, with peak levels at night. In the Indian pharmaceutical context, it is available as a dietary supplement and as a prescription drug (Schedule H) for specific indications. It plays a crucial role in synchronizing the sleep-wake cycle (circadian rhythm) and possesses antioxidant and immunomodulatory properties.
Adult: For insomnia (≥55 years): 2-5 mg, taken 1-2 hours before bedtime. For circadian disorders: 0.5-5 mg, timing is critical and should be guided by a physician. Typical starting dose is 1-2 mg.
Note: Take orally with or without food. For sleep initiation, take 30-60 minutes before desired bedtime. For jet lag, take at bedtime (destination time) after eastward travel or upon awakening after westward travel. Do not crush or chew controlled-release tablets. Sublingual tablets should be allowed to dissolve under the tongue.
Melatonin's primary mechanism is the agonist activity at melatonin receptors (MT1 and MT2) in the suprachiasmatic nucleus (SCN) of the hypothalamus, the body's master circadian clock. Activation of these receptors phase-shifts the circadian rhythm, promoting sleep initiation and regulating the timing of the sleep-wake cycle. It also has a mild hypothermic effect which may facilitate sleep.
Pregnancy: Category N (Not classified by US FDA). Animal studies are inconclusive. Use is contraindicated due to lack of adequate human data. Potential hormonal effects on fetal development are unknown.
Driving: May impair alertness, especially the next morning. Advise patients not to drive or operate machinery for at least 4-5 hours after ingestion or if feeling drowsy.
| Fluvoxamine | Markedly increases melatonin levels (potent CYP1A2 inhibitor), increasing risk of sedation. | Major |
| Other CYP1A2 inhibitors (Ciprofloxacin, Estrogens) | Increased melatonin exposure. | Moderate |
| CYP1A2 inducers (Carbamazepine, Rifampicin, Smoking) | Decreased melatonin exposure, reducing efficacy. | Moderate |
| Central Nervous System Depressants (Benzodiazepines, Z-drugs, Opioids, Alcohol) | Additive sedative effects, impairing cognitive and motor performance. | Major |
| Anticoagulants/Antiplatelets (Warfarin) | Melatonin may increase INR; monitor coagulation parameters. | Moderate |
| Antihypertensives (Nifedipine, Verapamil) | May potentiate hypotensive effect. | Moderate |
| Immunosuppressants (Cyclosporine, Tacrolimus) | Theoretical immunostimulatory effect of melatonin may reduce efficacy of immunosuppressants. | Moderate |
Same composition (Melatonin (NA)), different brands: