Melatonine Zentiva Lp (Melatonin)

Melatonin is a melatonin receptor agonist used to treat disorders of the sleep‑wake cycle.

• Insomnia: facilitates sleep onset and improves sleep continuity in individuals who have difficulty falling asleep.
• Jet lag: assists in resetting the circadian rhythm after rapid east‑west travel, reducing nighttime awakenings.
• Shift work disorder: supports adjustment of sleep timing for workers on irregular schedules, enhancing daytime alertness.
• Delayed sleep phase syndrome: helps advance bedtime and normalize sleep‑wake patterns in patients with delayed circadian phase.

• Melatonin acts as an agonist at the MT1 and MT2 melatonin receptors located in the suprachiasmatic nucleus of the hypothalamus. Activation of these receptors modulates the endogenous circadian clock, leading to a reduction in neuronal firing that promotes the onset of sleep and helps synchronize the sleep‑wake cycle with environmental light‑dark cues.

Melatonin is generally well tolerated, but some users may experience adverse reactions.

Common Side Effects

• Headache: mild headache may occur, usually transient.
• Dizziness: occasional light‑headedness or vertigo reported.
• Daytime sleepiness: feeling unusually drowsy during waking hours.
• Nausea: mild stomach upset or queasiness.
• Fatigue: persistent tiredness despite adequate rest.
• Vivid dreams: unusually intense or memorable dreams during sleep.

Serious or Rare Side Effects

• Allergic reactions: rash, itching, swelling, or angioedema requiring medical attention.
• Mood changes: rare episodes of depression or agitation.
• Hallucinations: very uncommon visual or auditory disturbances.
• Severe hypotension: marked drop in blood pressure leading to dizziness or fainting.

When using melatonin, certain precautions should be observed to ensure safety and effectiveness.

• Pregnancy: consult a healthcare professional before use, as safety data are limited.
• Breastfeeding: discuss potential risks with a physician, since melatonin may pass into milk.
• Concomitant CNS depressants: monitor for additive sedation when combined with alcohol or sedatives.
• Anticoagulant therapy: be aware of possible increased bleeding tendency and seek medical advice.
• Autoimmune disorders: use with caution, as melatonin may influence immune function.
• Store at ambient temperature: keep below 25 °C in the original packaging, protected from moisture and light.

Melatonin can interact with several medicines; awareness of major and moderate interactions helps avoid adverse effects.

Major Interactions (Avoid)

• Fluoxetine or other CYP1A2 inhibitors: may raise melatonin plasma levels, increasing risk of side effects.
• Warfarin: potential enhancement of anticoagulant effect, leading to increased bleeding risk.
• Immunosuppressants (e.g., cyclosporine): melatonin may reduce immunosuppressive efficacy.

Moderate Interactions (Monitor Closely)

• Benzodiazepines or other CNS depressants: additive sedation may occur.
• Antihypertensive agents: melatonin can augment blood‑pressure‑lowering effects.
• Oral contraceptives: may alter melatonin metabolism, affecting hormone balance.