Pharmacology and toxicology
 Mannitol as a single sugar in the body are not metabolized by the renal tubules after glomerular filtration is reabsorbed within a few, play penetration diuretic effect.
(1) organization dehydration. Increased plasma osmolality, resulting in the organization (including the eye, brain, cerebrospinal fluid, etc.) of water into the blood vessels, thereby reducing edema, reducing intraocular pressure, intracranial pressure and cerebrospinal fluid volume and pressure. Can produce infiltration 1g mannitol concentration 5.5mOsm, 100g mannitol injection can 2000ml of water transferred to the cells, the cells, the urinary sodium excretion 50g. (2) diuretic effect. Mechanism of the diuretic effects of mannitol in two aspects:
① mannitol increased blood volume, and to promote the secretion of prostaglandin I2, which expansion of renal blood vessels, increase blood flow, including renal medulla of renal blood flow. Expansion of the glomerular afferent arterioles, glomerular capillary pressure, glomerular filtration rate increased cortex.
② After the drug from the glomerular filtration rarely (<10%) by renal tubular reabsorption, it can increase the tubular fluid osmolality and reduce tubular water and Na +, Cl-, K +, Ca2 +, Mg2 + and other solute reabsorption. Major role in the past that the drug in the proximal tubule, but after the puncture animal experiments found that large doses of mannitol, the proximal tubule through the water and Na +, respectively, only increased 10% to 20% and 4% to 5%; to reach distal tubule of water and Na + were increased by 40% and 25%, suggesting that Heinz loop reabsorption of water and Na + to reduce the diuretic effects of mannitol in an important role. This may be due to renal medullary blood flow, medulla urea and Na + loss increased, thereby undermining the medullary osmotic gradients. As the tubular fluid flow after infusion of mannitol increased when certain drugs and toxic poisoning, the concentration of these substances fall within the tubular, reduced toxicity to the kidneys and excreted by the kidneys speed up.