Leeftijd als determinant van instabiliteit van lithiumconcentraties in serum

Abstract

OBJECTIVE To compare several parameters considered as proxies for instability between age groups. Lithium is used both in bipolar disorder and as augmentation in treatment of resistant unipolar depression. Long-term treatment is often indicated. Pharmacokinetic and pharmacodynamic changes in older age, as well as increasing prevalence of co-morbidities and polypharmacy, may result in instability of serum lithium concentrations. The parameters in this study were derived from studies involving oral anticoagulants. DESIGN Retrospective database study. METHODS A retrospective study (1995-2004) was conducted using serum lithium concentrations from the laboratories of three hospitals in the Netherlands. 759 patients treated with lithium, 40 years or older, with at least two years follow-up were included. They were divided into four age groups: 40-49 years, 50-59 years, 60-69 years and ≥ 70 years; the youngest group was used as a reference group. The variance growth rate and percentage of time below, in and above treatment range were considered proxies for instability. Number of days and number of serum lithium concentration measurements were considered proxies for instability during titration. They were all analysed between the age categories. RESULTS There was no significant difference for these variables between the reference group and the older age groups. In a subgroup of 454 patients, the parameters considered proxies for instability during titration were evaluated. No significant difference was found between the age groups. In a small group of 117 patients, titration and maintenance treatment for at least two years could be analysed separately. Also in this group, there was no difference between the age groups. CONCLUSION In this study, age was not a determinant of instability in serum lithium concentration. Therefore, age does not seem to be a reason to withhold or to discontinue lithium therapy. van Melick EJM, Souverein PC, den Breejen JH, Tusveld CE, Egberts TCG, Wilt