Hebei Messi Biology Co., Ltd. states that Magnesium Oxide (MgO) is sometimes used as a coating excipient in the pharmaceutical, food, and chemical industries. In coating applications, it mainly utilizes its specific physical and chemical properties. The following are its main uses and precautions:
Main Purposes and Advantages of Using Magnesium Oxide in Coating:
- pH Adjuster and Antacid: Magnesium oxide is a strongly alkaline substance. In gastric soluble coatings or certain functional coatings, it can be used to neutralize acidic environments or maintain a specific pH value. It is particularly suitable for protecting active pharmaceutical ingredients from gastric acid degradation or promoting dissolution in coating systems within the alkaline environment of the intestine (although enteric coatings typically use more established polymers such as cellulose acetate phthalate, hypromellose phthalate, etc.).
- Anti-Adherent/Glidant: Micronized magnesium oxide has extremely fine particles and good flowability, and can be used as an anti-adherent or glidant in coating solutions. During the film coating process, adding it to the coating solution can help reduce adhesion between tablets or granules, improve coating uniformity, especially in the later stages of coating or in high-solids formulations.
- Opacifier: Magnesium oxide is a white, opaque powder. Adding an appropriate amount of magnesium oxide to the coating formulation can increase the opacity and hiding power of the coating layer, improve the appearance of the final product (providing a more uniform white or background color), and help protect light-sensitive drug ingredients from light.
- Filler/Bulking Agent (Minor Role): In formulations where it is necessary to increase the thickness or solids content of the coating layer, magnesium oxide can be used as a relatively inert filler.
- Heat Stabilizer (Specific Applications): Magnesium oxide has a very high melting point (approximately 2852°C) and is chemically stable and resistant to high temperatures. It may provide a certain degree of thermal stability in coating systems that need to undergo high-temperature processing steps (such as certain melt coatings or thermosetting processes).
Magnesium Oxide is mainly used in coatings as:
- Functional Additive: As a powerful pH adjuster/antacid (especially for gastric acid protection), anti-adherent/glidant, opacifier, and sometimes as a filler or heat stabilizer.
- Requires Careful Use: Its strong alkalinity is the core limitation, easily causing API degradation and compatibility issues. It must usually be used in conjunction with an effective separating layer. It cannot form a film on its own and must be combined with mainstream polymers.
- Specific Scenario Applications: It should only be considered when its special functions are needed (such as strong antacid requirements, improved processability of highly viscous coating solutions, enhanced opacity) and the risks of its alkalinity can be effectively controlled.