Mannitol has been used for decades to reduce swelling around the eye or in the brain.

In my 40 years as an RN, I never used Mannitol as a diuretic, but I do know that it's sometimes used in Renal Units to force urine from the kidneys of patients in acute renal failure.

It has a long list of side effects, but as I don't know any more than that, I suggest you ask mrsD about it. I'm sure she'll be able to help you out.