What are the drug interactions of lithium?
• Because of lithium’s narrow therapeutic index, interactions with other drugs can be very important. The most commonly encountered interactions are with: • Diuretics: thiazide diuretics can increase serum lithium levels by reducing clearance of lithium. People who are stabilized on lithium and begin taking thiazide diuretics are at significant risk of developing lithium toxicity. Toxic lithium concentrations may be seen within 3–5 days. Loop diuretics also cause lithium retention but are less likely to result in lithium toxicity. • Nonsteroidal anti-inflammatory drugs (NSAIDs) may increase serum lithium levels by up to 40%. The mechanism of this interaction is thought to be related to the effects of NSAIDs on fluid balance. This is particularly important if NSAIDs are added to a long-standing prescription of lithium. • Haloperidol: although severe neurotoxicity has been reported with this combination, if lithium levels are maintained in the therapeutic range (0.6–1.0 mmol/L) and the h
