Glycerin + Mannitol is a combination of two medicines: Glycerin + Mannitol1 and Glycerin + Mannitol2 which treat increased pressure in the skull/brain. Glycerin + Mannitol2 is an osmotic diuretic which draws water out of tissues in the brain and decreases swelling around the brain. Addition of Glycerin + Mannitol1 prevents the swelling from coming back which may possibly occur with plain Glycerin + Mannitol2
