What is the interaction between lithium and NSAIDs?

• A. Increased risk of lithium toxicity (e.g., ibuprofen, naproxen)
• B. Decreased lithium serum levels
• C. No significant interaction
• D. Lithium is converted to an inactive metabolite

Answer: (A)

When thinking about lithium and NSAIDs, the important idea is how NSAIDs affect kidney handling of lithium. Lithium is cleared mainly by the kidneys and behaves like sodium. NSAIDs inhibit renal prostaglandin synthesis, which reduces renal blood flow and the glomerular filtration rate. This shift leads to more lithium reabsorption in the proximal tubule as the kidneys try to conserve sodium, raising serum lithium levels. The result is an increased risk of lithium toxicity with NSAID use, especially with ongoing use of drugs like ibuprofen or naproxen.

Clinically, watch for signs of toxicity such as tremor, GI upset, confusion, ataxia, or altered mental status. If NSAIDs are necessary, monitor lithium levels closely and consider safer analgesics like acetaminophen when possible.