🌙 Melatonin is a “body-clock” hormone used to help sleep onset and circadian timing.
🇬🇧 In the UK, the common licensed adult use is prolonged-release melatonin 2 mg for short-term primary insomnia in adults ≥55
(usually up to 13 weeks). Always check the BNF
and follow local formulary rules (many ICBs restrict prescribing outside the licensed indication).
📘 About: Always check the BNF
- 📚 BNF: Melatonin
- ✅ Licensed adult insomnia use (UK): prolonged-release 2 mg in adults ≥55 for short-term primary insomnia.
- 👶 Paediatric use is often specialist-initiated and product-specific (e.g. ASD/ADHD pathways); dosing and licensing depend on formulation.
⚙️ Mode of action
- 🕰️ Acts on MT1/MT2 receptors in the suprachiasmatic nucleus → helps sleep initiation and circadian alignment.
- 🧩 Particularly helpful when insomnia is driven by circadian delay (late sleep onset) rather than pain/breathlessness/delirium.
- 💊 Prolonged-release preparations aim to mimic the body’s overnight melatonin profile.
✅ Indications (common UK practice)
- 🌙 Primary insomnia in adults ≥55 (licensed, short-term).
- ✈️ Jet lag / circadian rhythm disturbance (use is formulation-dependent; follow BNF/local guidance).
- 👶 Neurodevelopmental insomnia (e.g. ASD/ADHD): usually specialist-led with strict sleep-hygiene prerequisites and review plans.
💊 Dose range: short-term use (adult insomnia ≥55)
| Name |
Typical dose |
Frequency |
Route |
How to take |
| Melatonin prolonged-release (e.g. Circadin MR) |
2 mg |
Nocte |
PO |
⏱️ Take 1–2 hours before bedtime (often after food). Swallow whole — do not crush. |
🔁 Review early: if no meaningful benefit after ~3 weeks (or local policy), stop rather than continuing indefinitely.
If it helps, keep within the intended short-term course unless specialist advice supports longer.
🔗 Interactions (high-yield)
- 🚫 Fluvoxamine: can markedly increase melatonin exposure — avoid (BNF lists as severe).
- 🧪 CYP1A2 inhibitors (e.g. ciprofloxacin, oestrogens) may increase melatonin levels → more next-day drowsiness.
- 🩸 Warfarin/anticoagulants: possible INR effect — monitor INR if co-prescribed.
- 😴 Additive sedation with benzodiazepines, Z-drugs, opioids, antihistamines, alcohol.
⚠️ Cautions
- 🧓 Older adults: falls risk if morning grogginess, dizziness, or nocturia worsens — start when they can trial safely.
- 🫘 Hepatic impairment: exposure may be higher (check BNF; consider avoiding in severe liver disease).
- 🧠 Epilepsy: rare reports of increased seizure activity — use specialist advice if relevant.
- 🤰 Pregnancy/breastfeeding: avoid unless specialist recommendation (limited safety data).
⛔ Contraindications
- 📚 Product-specific — see BNF and local formulary.
- ⚠️ Practical “contraindication”: unaddressed causes of poor sleep (pain, nocturia, OSA, depression, delirium, stimulants) — fix these first.
😵 Side effects
- 🤕 Headache, dizziness, nausea.
- 😴 Somnolence / next-day drowsiness, vivid dreams.
- 🦴 Occasional: joint pain, fatigue, irritability.
🩺 Practical prescribing tips
- 🧼 Always pair with sleep hygiene (light exposure in the morning, consistent wake time, minimise late caffeine/screens).
- 🕰️ If the problem is sleep phase delay, timing matters more than dose — take it earlier, not higher.
- 🧾 Document: indication, formulation (IR vs MR), start date, review date, and stop plan.
📖 References
🛠️ Revisions
