Melatonin
Melatonin is a hormone that also exists as a licensed medicine, which is why the information available about it varies so much in quality. Where it is licensed, the UK summary of product characteristics sets out two specific indications and a set of timing rules, and those rules do more work than the dose does.
Melatonin Tablets
Circadian Rhythm Sleep Disorders
3mg
Indicated to address sleep cycle disturbances to manage circadian rhythm and support natural skeletal hormone levels.
Key points
- The SmPC indicates it for short term treatment of jet lag in adults, and for insomnia in children and adolescents aged 6 to 17 years with ADHD, where sleep hygiene measures have been insufficient.
- For jet lag the recommended dose is 1 to 5 mg for a maximum of 5 days, taken at destination bedtime for journeys of 5 time zones or longer.
- Timing is not a detail: incorrectly timed intake can have no effect, or an adverse effect, on re-synchronisation, so it should not be taken before 20:00 or after 04:00 at destination.
- In children and adolescents with ADHD, treatment should be initiated by physicians experienced in ADHD and/or paediatric sleep medicine.
How it works
Melatonin is involved in the timing of the sleep-wake cycle rather than in sedation as such. That distinction explains the timing rules: the same dose can help or hinder depending on when in the night it is taken, because what is being shifted is a rhythm rather than a level of alertness.
The SmPC makes that explicit for jet lag, warning of the potential for incorrectly timed intake to have no effect, or an adverse effect, on re-synchronisation. A sleeping tablet taken at the wrong hour is merely poorly timed; melatonin taken at the wrong hour can move the clock the wrong way.
Safety specific to melatonin
Drowsiness. The SmPC states that melatonin may cause drowsiness, and that melatonin tablets should be used with caution if the effects of drowsiness are likely to be associated with a risk to patient safety.
Alcohol. Because alcohol can impair sleep and potentially worsen certain symptoms of jet lag such as headache, morning fatigue and concentration, the SmPC recommends that alcohol is not consumed when taking it.
Autoimmune disease. Occasional case reports have described exacerbation of an autoimmune disease in patients taking melatonin, and there are no data regarding use of melatonin tablets in patients with autoimmune diseases. The hedge is the SmPC’s own: case reports exist, evidence does not.
Liver and kidneys. It is not recommended in patients with moderate or severe hepatic impairment. The effect of any stage of renal impairment on melatonin pharmacokinetics has not been studied, and caution should be used in patients with renal impairment.
Fluvoxamine. Concomitant treatment with melatonin and the CYP1A2 inhibitor fluvoxamine, which also inhibits CYP2C19, should be avoided.
Dosing limits worth knowing
For jet lag, a maximum of 16 treatment cycles may occur per year. For insomnia in children and adolescents with ADHD, the recommended starting dose is 1 to 2 mg taken 30 to 60 minutes before bedtime, which may be increased by 1 mg every week until effect up to a maximum of 5 mg per day independent of age, and the lowest effective dose should be sought.