Learn about mannitol including mannitol mechanism of action & dose. What are medical uses of mannitol injection and mannitol powder. What are contraindications, side effects and adverse effects. Mannitol injection is used to lower pressure in the head (intracranial pressure) or pressure in the eye (intraocular pressure). It is also used to treat swelling of the brain (cerebral edema). Mannitol Injection, USP is a sterile, nonpyrogenic solution of mannitol in water for injection available in a concentration of 20% in flexible plastic containers. A healthcare provider will give you this injection in a hospital or clinic setting. It treats swelling from heart, kidney or liver disease or swelling around your brain or in your eyes.