A 78-year-old man on lithium for bipolar disorder is started on bendroflumethiazide. What is the main risk?
Answer and explanation
Correct answer: A. Lithium toxicity because thiazides reduce renal lithium clearance
- Step 1: Thiazides, ACE inhibitors and NSAIDs raise lithium levels.
- Step 2: Level monitoring and avoiding the combination is advised.
Answer
Lithium toxicity because thiazides reduce renal lithium clearance.
Why not the others: No interaction exists: This interaction is clinically significant. Lithium becomes ineffective: The interaction raises, not lowers, levels. Hypoglycaemia: Hypoglycaemia is not the issue.
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