Which drug is often used as adjunctive therapy to reduce the incidence of rebound from mannitol?

• A. Diphenhydramine
• B. Phenytoin
• C. Furosemide
• D. Mannitol

Answer: (C)

Osmotic therapy with mannitol lowers intracranial pressure by drawing water out of brain tissue, but when its effects wear off, fluid can reaccumulate in the brain, causing rebound intracranial hypertension. Using a loop diuretic such as furosemide as an adjunct helps sustain diuresis and reduce overall fluid volume, including potential CSF production, which helps blunt or prevent that rebound rise in ICP. This makes furosemide the best choice to mitigate rebound after mannitol therapy. The other drugs shown don’t address the rebound mechanism: diphenhydramine is mainly an antihistamine with no role here, phenytoin is for seizure prophylaxis, and continuing mannitol itself would not prevent rebound.