Magnesium stearate white loose fine powder, feels slippery, insoluble in water, ethanol and ether, soluble in hot water, ether, decomposed into stearic acid and corresponding magnesium salts in case of acid. The solubility in room temperature water is 77-79mg/L, soluble in hot ethanol. Slightly smelly, there is a sense of slipperiness.
Magnesium stearate for tablets should pay attention to the dosage and mixing time:
Magnesium stearate is widely used as a lubricant for tablets and adhesives. However, due to its hydrophobic nature and its ability to prevent the drug from dissolving from the solid dosage form, its concentration should be minimized as much as possible in the prescription, and the dosage is generally 0.1% to 1%. Especially in direct opioid prescriptions, the amount of stearic acid used must not exceed 0.5%, otherwise the tablets will have a softening effect.
When tableting, the amount of lubricant magnesium stearate can directly affect the elastic deformation of the tablet, when the amount of lubricant is small, the proportion of its elastic deformation is also small, therefore, the addition of an appropriate amount of lubricant can make the tablet have good fluidity and compressibility.
When magnesium stearate and tablet granules are mixed, increasing the mixing time will reduce the dissolution rate and brittleness of the tablet, therefore, the mixing time of magnesium stearate should be carefully controlled, because magnesium stearate is compatible with strong acids, strong bases and iron salts, so it should not be used in pharmaceutical preparations containing assrin, certain vitamins, and most alkaloid salts.
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