Paediatric Off-Label Use of Melatonin--A Register Linkage Study between the Norwegian Prescription Database and Patient Register.

The aims were, for the entire Norwegian population aged 4-17 years, to study the prevalence of melatonin use during 2004-2012, recurrent use in incident users and psychiatric and neurological morbidity in recurrent users. Data on dispensed melatonin were retrieved from the Norwegian Prescription Database and linked to diagnostic data from the Norwegian Patient Register. Outcome measures were the following: 1-year prevalence of use, proportion of recurrent use (use over three consecutive 365-day periods among incident users in 2009) and annual number of milligrams and number of prescriptions dispensed in recurrent users. The prevalence of registered ICD-10 diagnoses during the period of 2008-2012 was given for the recurrent users. The prevalence of melatonin use increased annually in both genders during 2004-2012 (boys: 3.4-11.0 per 1000; girls: 1.5-7.7 per 1000). Twenty-nine per cent of boys and 23% of girls were recurrent melatonin users, with highest level of recurrent use among the youngest (aged 4-8 years; boys: 47%, girls: 42%). In the third year, the median annual amount of melatonin dispensed was 1080 (IQR 586-1800) milligrams in boys and 900 (IQR 402-1620) milligrams in girls. Among recurrent users, 91% had a diagnosis of either psychiatric (84%) or neurological (32%) disorder. Off-label recurrent use of melatonin seems to have acquired a role mainly in treating secondary sleep problems in children and adolescents with psychiatric and neurological disorders. Once melatonin has been started, a large proportion of patients continue for at least 3 years, in doses corresponding to daily use in the majority.