BACKGROUND: Age-dependent changes in lithium pharmacokinetic and pharmacodynamic properties can influence lithium use in an aging population, especially as newer treatment options are available. OBJECTIVE: We compared lithium use patterns between mddle-aged and elderly outpatients in the Netherlands. METHODS: Data for this study were obtained from the Dutch PHARMO Record Linkage System. Incident lithium users 40 years or older were identified in the period 1996-2008. The following lithium use patterns were defined: continuation, add on, switch, and discontinuation. Differences were assessed for the following age groups: 40 to 49 years, 50 to 59 years, 60 to 69 years, and 70 years or older. The youngest group was the reference group. Patient baseline characteristics and potential determinants of changes in lithium use patterns were assessed. RESULTS: We identified 2081 incident lithium users. Use of antidepressants was not different at baseline between age groups, but elderly patients starting lithium treatment used baseline antipsychotics less frequently (P < 0.05). Older patients were less likely to receive psychotropic drugs as add on to ongoing lithium therapy (P < 0.05). Frequency of discontinuation and switch events did not differ betweenthe age groups. In the whole study group, age was associated with any change in lithium use patterns. CONCLUSIONS: Older patients are less likely to receive psychotropic drugs as add on to ongoing lithium therapy. Despite pharmacokinetic and pharmacodynamic changes in the elderly, lithium is not more often discontinued and not more often switched in older patients.