Drug-induced lithium toxicity in the elderly: a population-based study

Objectives: To study the association between hospital admission for lithium toxicity and the use of diuretics, angiotensin‐converting enzyme (ACE) inhibitors, and nonsteroidal antiinflammatory drugs (NSAIDs) in the elderly. Design: Population‐based nested case‐control study. Setting: Ontario, Canada. Participants: Ontario residents aged 66 and older treated with lithium. Measurements: Estimated relative risk of hospital admission for lithium toxicity. Results: From January 1992 to December 2001, 10,615 elderly patients continuously receiving lithium were identified, of whom 413 (3.9%) were admitted to the hospital at least once for lithium toxicity. After adjustment for potential confounders, a dramatically increased risk of lithium toxicity was seen within a month of initiating treatment with a loop diuretic (relative risk (RR)=5.5, 95% confidence interval (CI)=1.9–16.1) or an ACE inhibitor (RR=7.6, 95% CI=2.6–22.0). Conversely, neither thiazide diuretics nor NSAIDs were independently associated with a significantly increased risk of hospitalization for lithium toxicity. Conclusion: The use of loop diuretics or ACE inhibitors significantly increases the risk of hospitalization for lithium toxicity, particularly in naïve recipients.