Which drug may decrease the blood levels of lithium?

Which drug may decrease the blood levels of lithium?

• A. Ibuprofen
• B. Azithromycin
• C. Lansoprazole
• D. Acetazolamide

Answer: (D)

Lithium blood levels are shaped by how the kidneys handle sodium and water. Lithium is filtered and then reabsorbed in the proximal tubule together with sodium. When a drug increases sodium delivery to the distal parts of the nephron or increases overall diuresis, more lithium is excreted and its serum level falls. Acetazolamide inhibits carbonic anhydrase in the proximal tubule, causing bicarbonate loss, natriuresis, and diuresis. This shifts renal handling in a way that reduces lithium reabsorption and increases lithium excretion, lowering its blood level. That’s why acetazolamide can decrease lithium levels. The other options don’t have this effect in typical practice. NSAIDs like ibuprofen tend to raise lithium levels by reducing renal clearance, while azithromycin and lansoprazole do not reliably lower lithium levels.

Lithium blood levels are shaped by how the kidneys handle sodium and water. Lithium is filtered and then reabsorbed in the proximal tubule together with sodium. When a drug increases sodium delivery to the distal parts of the nephron or increases overall diuresis, more lithium is excreted and its serum level falls.

Acetazolamide inhibits carbonic anhydrase in the proximal tubule, causing bicarbonate loss, natriuresis, and diuresis. This shifts renal handling in a way that reduces lithium reabsorption and increases lithium excretion, lowering its blood level. That’s why acetazolamide can decrease lithium levels.

The other options don’t have this effect in typical practice. NSAIDs like ibuprofen tend to raise lithium levels by reducing renal clearance, while azithromycin and lansoprazole do not reliably lower lithium levels.