Use of lithium in the adult populations of Denmark, Norway and Sweden.

Background: Lithium is an important drug in the treatment of bipolar disorder. Earlier epidemiological studies of lithium use have depended on sales statistics, clinical surveys or population surveys. The national prescription databases in Denmark, Norway and Sweden may help provide more reliable information on the epidemiology of lithium use.

Methods: Data were taken from the three national prescription databases in Denmark, Norway and Sweden from July 2005 until June 2006, encompassing 1 year of prescription data. Similar methods were used to identify a number of different pharmacoepidemiological measures and data were collected for adults aged 18-69 at the time of prescription.

Results: Norway and Sweden had higher sales and more prevalent use than Denmark. In all three countries, more female than males were treated and the prevalence of use increased linearly with age. In all, 0.17, 0.21, and 0.25% of the populations in Denmark, Norway and Sweden respectively redeemed at least 1 prescription for lithium in the period studied. The amount prescribed per user per year varied with age, increasing to maximum doses at 40 years of age and then decreasing.

Conclusion: This study is the first attempt to use prescription databases in all three Scandinavian countries to describe in detail the epidemiology of a drug's use. The analysis revealed subtle differences in the clinical use of lithium that cannot be explained by differences in the epidemiology of bipolar disorder.