Skip to content
ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Melatonin Receptor Agonist — Hypnotic Pregnancy: §4.6: no clinical data on exposed pregnancies are available; animal studies do not indicate direct or indirect harmful effects. In view of the lack of clinical data, use in pregnant women and by women intending to become pregnant is not recommended. Breastfeeding: exogenous melatonin is probably secreted into human milk, and breast-feeding is not recommended in women under treatment with melatonin.

Melatonin Modified-Release (Elderly Insomnia)

Brand names: Circadin

Modified-release melatonin is a hormone preparation licensed for the short-term treatment of primary insomnia, notably in older adults.

Adult dose

Dose: Insomnia (this page: modified-release melatonin in older adults) — Circadin 2 mg prolonged-release tablets. §4.2 verbatim: 'The recommended dose is 2 mg once daily, 1-2 hours before bedtime and after food. This dosage may be continued for up to thirteen weeks.' 2 mg once daily is the only dose stated anywhere in the fetched §4.2.
Route: Oral. §4.2 verbatim: 'Oral use. Tablets should be swallowed whole to maintain prolonged release properties. Crushing or chewing should not be used to facilitate swallowing.'
Frequency: Once daily, 1-2 hours before bedtime and after food.
Max: 2 mg daily — the only dose stated for this product; the fetched posology gives no higher dose and no dose titration. Duration: this dosage may be continued for up to thirteen weeks.
Source: UK SPC (eMC) for Circadin 2 mg Prolonged-release Tablets, §4.2 posology plus §4.3, §4.4/4.5, §4.6 and §4.8 (https://www.medicines.org.uk/emc/product/2809/smpc). The §4.2 POSOLOGY SECTION IS COMPLETE in this bundle (it runs through to Method of Administration). Some sections of the product information we used were incomplete — check the full SPC. §4.1 (therapeutic indications) was not fetched, so the licensed indication wording and the licensed age band could not be quoted; the indication above is this page's own. RENAL: 'The effect of any stage of renal impairment on melatonin pharmacokinetics has not been studied. Caution should be used when melatonin is administered to such patients.' HEPATIC: 'There is no experience of the use of Circadin in patients with liver impairment... Circadin is not recommended for use in patients with hepatic impairment.' §4.4: 'Circadin may cause drowsiness. Therefore the product should be used with caution if the effects of drowsiness are likely to be associated with a risk to safety.' NOTE ON SOURCES: providers.openfda and providers.who are both null in this bundle — no US label and no WHO entry were used.

Paediatric dose

NO PAEDIATRIC DOSE EXISTS IN THIS SOURCE, so dosePerKg is null and the weight calculator is deliberately left unset. §4.2 verbatim: 'Paediatric population. The safety and efficacy of Circadin in children aged 0 to 18 years has not yet been established. Other pharmaceutical forms/strengths may be more appropriate for administration to this population. Currently available data are described in section 5.1.' No figure for any age under 18 appears anywhere in the fetched text. Any paediatric use is outside this product's licence — verify against a children's formulary and specialist paediatric guidance.

Dose adjustments

Renal

§4.2: 'The effect of any stage of renal impairment on melatonin pharmacokinetics has not been studied. Caution should be used when melatonin is administered to such patients.' No dose adjustment is stated.

Hepatic

§4.2: 'There is no experience of the use of Circadin in patients with liver impairment. Published data demonstrates markedly elevated endogenous melatonin levels during daytime hours due to decreased clearance in patients with hepatic impairment. Therefore, Circadin is not recommended for use in patients with hepatic impairment.'

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients listed in section 6.1 — the only contraindication listed in §4.3
  • NOT A §4.3 CONTRAINDICATION but §4.2 states Circadin is not recommended for use in patients with hepatic impairment
  • NOT A §4.3 CONTRAINDICATION but §4.4 states Circadin is not recommended for use in patients with autoimmune diseases (no clinical data exist in this group)
  • Contains lactose — §4.4: patients with rare hereditary problems of galactose intolerance, the LAPP lactase deficiency or glucose-galactose malabsorption should not take this medicine

Side effects

  • Most common adverse reactions in clinical trials: headache, nasopharyngitis, back pain and arthralgia (common in both the Circadin and placebo groups)
  • Nervous system (uncommon): migraine, headache, lethargy, psychomotor hyperactivity, dizziness, somnolence
  • Psychiatric (uncommon): irritability, nervousness, restlessness, insomnia, abnormal dreams, nightmares, anxiety
  • Psychiatric (rare): mood altered, aggression, agitation, crying, stress symptoms, disorientation, early morning awakening, libido increased, depressed mood, depression
  • Nervous system (rare): syncope, memory impairment, disturbance in attention, dreamy state, restless legs syndrome, poor quality sleep, paraesthesia
  • Gastrointestinal (uncommon): abdominal pain, abdominal pain upper, dyspepsia, mouth ulceration, dry mouth, nausea
  • Cardiac/vascular (rare): angina pectoris, palpitations; hypertension (uncommon), hot flush (rare)
  • Blood (rare): leukopenia, thrombocytopenia; immune: hypersensitivity reaction
  • Eye (rare): visual acuity reduced, vision blurred, lacrimation increased; ear: vertigo, positional vertigo
  • Skin (uncommon): dermatitis, night sweats, pruritus, rash, pruritus generalised, dry skin
  • This side-effect list may be incomplete — check the full SPC.

Interactions

  • Fluvoxamine increases melatonin levels (17-fold higher AUC, 12-fold higher serum Cmax) by inhibiting CYP1A2 and CYP2C19 — the combination should be avoided
  • 5- or 8-methoxypsoralen (5-MOP, 8-MOP) increases melatonin levels by inhibiting its metabolism — caution
  • Cimetidine (a CYP2D inhibitor) increases plasma melatonin levels — caution
  • Oestrogens (e.g. contraceptives or HRT) increase melatonin levels by inhibiting CYP1A1/CYP1A2 metabolism — caution
  • CYP1A2 inhibitors such as quinolones may increase melatonin exposure
  • CYP1A2 inducers such as carbamazepine and rifampicin may reduce plasma melatonin concentrations
  • Cigarette smoking may decrease melatonin levels by inducing CYP1A2
  • Alcohol should not be taken with Circadin (§4.5 pharmacodynamic interactions — the sentence was cut mid-way at the fetch limit)
  • Melatonin has been observed to induce CYP3A in vitro at supra-therapeutic concentrations; the clinical relevance is unknown
  • This interaction list may be incomplete — check the full SPC.

Monitoring

  • No laboratory monitoring is specified in the fetched sections
  • Drowsiness — §4.4: use with caution where the effects of drowsiness are likely to be associated with a risk to safety (relevant to falls and driving in older patients)
  • Duration — §4.2 states the dosage may be continued for up to thirteen weeks; review at that point

Clinical monograph

How it works

Melatonin is an endogenous hormone that acts on melatonin receptors involved in regulating the sleep-wake cycle and circadian rhythm.

Prescribing in practice

  • Melatonin can cause daytime drowsiness, so patients should be cautioned about driving or operating machinery if affected, which is especially relevant in frail older people at risk of falls.
  • It is intended for short-term use, with the need for continued treatment reviewed regularly.
  • It is metabolised hepatically and concentrations can be affected by drugs that inhibit or induce its metabolism, including fluvoxamine.

Monitoring

Review sleep response, daytime functioning and continued need for treatment periodically, with attention to falls risk in the elderly.

Counselling the patient

  • Take the modified-release tablet whole, after food, shortly before bedtime.
  • Be cautious with driving or hazardous tasks if you feel drowsy the next day.

Evidence & guidelines

Modified-release melatonin is licensed for short-term primary insomnia and supported by NICE guidance in older adults.

Reference: NICE TA739 (Melatonin for Insomnia 2021); Circadin SPC; Leger et al. BMJ 2004; AGS Beers Criteria 2023; STOPP/START v3; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Drugs
Pathways