Magnesium stearate is a loose white powder with a smooth feel. It is insoluble in water, ethanol and ether, but soluble in hot water and ether. It decomposes into stearic acid when exposed to acid. and the corresponding magnesium salts. The solubility in room temperature water is 77-79 mg/L, and it is soluble in hot ethanol. It has a slight odor and a greasy feel.
When magnesium stearate is used in tablets, attention should be paid to the dosage and mixing time:
Magnesium stearate is widely used as a lubricant for tablets and adhesives. However, because it is hydrophobic and can block the dissolution of drugs from solid dosage forms, its concentration should be minimized in the prescription, and the dosage is generally 0.1% to 1%. Especially in direct opium prescriptions, the amount of stearic acid used must not exceed 0.5%, otherwise it will produce a softening effect on the tablets.
When compressing tablets, the amount of lubricant magnesium stearate can directly affect the elastic deformation of the tablet. When the amount of lubricant is small, its elasticity will decrease. The proportion of deformation is also small, so adding an appropriate amount of lubricant can make the tablets have good fluidity and compressibility.
When mixing magnesium stearate and tablet particles, increasing the mixing time will reduce the dissolution rate and brittleness of the tablets. Therefore, the hardness should be carefully controlled. The mixing time of magnesium stearate is because magnesium stearate is incompatible with strong acids, strong bases and iron salts, so it cannot be used in pharmaceutical preparations containing aspirin, certain vitamins, and most alkaloid salts.
