Pharmacology and toxicology of mannitol
Release time:
2024-07-19
The drug is rarely (<10%) reabsorbed by renal tubules after glomerular filtration, so it can increase the osmotic concentration of renal tubules and reduce the reabsorption of water, Na +, Cl-, K +, Ca2 +, Mg2 + and other solutes by renal tubules. In the past, it was believed that this drug mainly acts on the proximal tubule, but after puncture animal experiments, it was found that after the application of large doses of mannitol, the water and Na + passing through the proximal tubule only increased by 10% ~ 20% and 4% ~ 5% respectively. However, the water and Na + reaching the distal tubule increased by 40% and 25% respectively, it suggests that water reabsorption and Na + reduction in Heinz loop play an important role in the diuretic effect of mannitol. This may be due to increased renal medullary blood flow and increased intramedullary urea and Na + loss, thereby disrupting the medullary osmotic pressure gradient. Due to the increase in tubular fluid flow after infusion of mannitol, when certain drugs and poisons are poisoned, the concentration of these substances in the renal tubules decreases, the toxicity to the kidneys decreases, and the excretion through the kidneys accelerates.
Mannitol is a monosaccharide, which is not metabolized in the body. It is rarely reabsorbed in the renal tubules after glomerular filtration, and plays a role in osmotic diuresis.
1. Tissue dehydration. Increase plasma osmotic pressure, resulting in tissue (including eyes, brain, cerebrospinal fluid, etc.) water into the blood vessels, thereby reducing tissue edema, reduce intraocular pressure, intracranial pressure and cerebrospinal fluid volume and pressure. 1g mannitol can produce osmotic concentration of 5.5mmol/L, injection of 100g mannitol can make 2000 mL intracellular water transfer to the outside of the cell, urinary sodium excretion of 50g.
2, diuretic effect. The diuretic mechanism of mannitol is twofold:
(1) Mannitol increases blood volume and promotes prostaglandin I2 secretion, thereby dilating renal blood vessels and increasing renal blood flow, including renal medulla blood flow. Glomerular entry arterioles dilated, glomerular capillary pressure increased, and cortical glomerular filtration rate increased.
(2) The drug is rarely (<10%) reabsorbed by renal tubules after glomerular filtration, so it can increase the osmotic concentration of renal tubular fluid and reduce the reabsorption of water, Na +, Cl-, K +, Ca2 +, Mg2 + and other solutes by renal tubules. In the past, it was believed that this drug mainly acts on the proximal tubule, but after puncture animal experiments, it was found that after the application of large doses of mannitol, the water and Na + passing through the proximal tubule only increased by 10% ~ 20% and 4% ~ 5% respectively. However, the water and Na + reaching the distal tubule increased by 40% and 25% respectively, it suggests that water reabsorption and Na + reduction in Heinz loop play an important role in the diuretic effect of mannitol. This may be due to increased renal medullary blood flow and increased intramedullary urea and Na + loss, thereby disrupting the medullary osmotic pressure gradient. Due to the increase in tubular fluid flow after infusion of mannitol, when certain drugs and poisons are poisoned, the concentration of these substances in the renal tubules decreases, the toxicity to the kidneys decreases, and the excretion through the kidneys accelerates.
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