A patient on lithium who has recently started a thiazide diuretic should prompt urgent medical review due to potential toxicity. Which option describes the correct action?

• A. Refer urgently for possible lithium toxicity
• B. Ignore and continue
• C. Stop lithium
• D. Increase lithium dose

Answer: (A)

When lithium is used with a thiazide diuretic, lithium levels can rise because the drug alters renal handling of sodium and lithium. This increases the risk of lithium toxicity, which can develop gradually and present with tremor, confusion, GI symptoms, or worse. Therefore, the appropriate action is to refer urgently for possible lithium toxicity so a clinician can check the serum lithium level, kidney function, and electrolytes, and decide on appropriate management (adjusting or stopping the diuretic or lithium, or switching to another antihypertensive).

Ignoring the interaction, stopping lithium without assessment, or increasing the lithium dose would all be inappropriate because they don’t address the potential toxicity risk and could lead to harm.