Abstract

A 6½-year-old boy weighing 28 kg is taking melatonin 10.5 mg at night for insomnia associated with autistic spectrum disorder. There is concern that regular administration of this dose may be harmful as the British National Formulary (BNF) for children recommends a maximum of 10 mg daily. The drug is unlicensed in children and a wide range of doses has been used in small-scale clinical studies. One systematic review and meta-analysis of small-scale studies of melatonin for sleep disorders in autistic spectrum disorder found that in patients aged 2–18 years the dosage of melatonin ranged from 0.75 mg to 15 mg with occasional use of 25 mg. There is very limited evidence for using doses in excess of 10 mg daily. However, melatonin has not been shown to be associated with severe adverse effects over a wide range of doses, therefore a dose of 10.5 mg daily for a 6½-year-old child is unlikely to cause significant harm.