Final answer:
Mannitol is an osmotic diuretic that is used to reduce brain swelling. It works by decreasing blood pressure, increasing glomerular filtration rate, and decreasing sodium reabsorption in the kidneys.
Step-by-step explanation:
Osmotic diuretics, such as mannitol, promote water loss by osmosis. Mannitol is often administered to reduce brain swelling after head injury. It acts as a vasodilator, decreasing blood pressure and increasing glomerular filtration rate, which leads to increased urine output. Additionally, mannitol decreases sodium reabsorption in the kidneys, further promoting water loss.