Which medication should be avoided with lithium due to potential interaction?

• A. Acetaminophen
• B. Aspirin
• C. Penicillin
• D. NSAIDs

Answer: (D)

When lithium is used, its clearance by the kidneys is crucial to prevent toxicity. Medications that alter kidney function can tip the balance. NSAIDs interfere with renal prostaglandins, which reduces renal blood flow and the glomerular filtration rate. Because lithium is handled by the kidneys in a way related to sodium reabsorption, this reduction in kidney function leads to decreased lithium excretion and higher lithium levels in the blood. That increase raises the risk of lithium toxicity, making NSAIDs something to avoid while on lithium therapy.

Acetaminophen is generally considered safer with lithium because it does not significantly affect renal lithium clearance. Penicillin doesn’t typically alter lithium levels via the kidney, so it doesn’t carry the same toxicity risk. If pain relief is needed during lithium treatment, acetaminophen is the preferred option, while NSAIDs should be avoided to protect lithium balance. Signs of rising lithium levels to watch for include tremor, confusion, ataxia, and GI symptoms; maintaining hydration and normal salt intake helps minimize fluctuations in lithium levels.