Differences in lithium use patterns in the Netherlands: comparing middle-aged and older patients in a database study.

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 middle-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 between the 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.