Drug-drug interactions between lithium and antihypertensive and anti-inflammatory drugs

Introduction Lithium is the gold standard in treating bipolar disorders. As patients become increasingly older, drug-drug interactions leading to decreased excretion of lithium represent a key issue in lithium safety.

Methods To quantify the impact of potentially interacting drugs (diuretics, ACE inhibitors, AT1 antagonists and non-steroidal anti-inflammatory drugs) on lithium serum levels in addition to age, sex, sodium and potassium serum levels as well as renal function.

Patients and methods: Retrospective data of lithium serum levels were analyzed in 501 psychiatric inpatients (2008 – 2015) by means of linear regression modelling

Results The number of interacting drugs was significantly associated with serum levels of lithium in addition to the established factors age, renal function and sodium concentration. Additionally, absolute lithium levels were dependent on sex. However, only NSAIDs were identified to increase absolute lithium levels independently

Conclusion Routine clinical practice needs to focus especially on NSAIDs as over-the-counter medication that may lead to an increase in lithium serum concentration. Patients taking lithium should be informed about possible intoxications due to NSAIDs.