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Magnesium Stearate: Relating Physicochemical Properties to Functional Properties Such as Dissolution

Researchers at the Center for Pharmaceutical Development (CPD) have been performing research to enable the pharmaceutical manufacturers make more effective tablets.

One of the most common ingredients in a tablet is magnesium stearate. Magnesium stearate is structurally similar to sodium stearate, which is better known as soap. This is used as a lubricant for the tablet press to ensure that the tablet releases properly after it is compressed. Its lubrication properties come from its fatty acid composition of stearates, palmitates, and other fatty acids.

Magnesium stearate is extremely difficult to study because it is both a complex mixture of chemical species and it can exist in multiple forms each of which have different properties. Compounding the situation is the fact that it is present in very low quantities in most tablets; making it even more difficult to study. CPD researchers have synthesized their own magnesium stearate so that they can both better understand how magnesium stearate’s composition affects the tablet properties and also study how it changes form once it is compressed into tablets.

By understanding how magnesium stearate affects the tablet making process, companies can better predict how to add it into the mix, at what ratios, and what grades to get the optimal tablet without loss of product from malformed tablets and to make safer and better tablets that will help patients.

Magnesium stearate is an extremely problematic additive to study because of its complex nature and low concentration in a tablet. With the CPD approach of making our own magnesium stearate enables us to study it using advanced analytical techniques that have not been used to study it previously. Most importantly, we can now study what happens to the magnesium stearate when it is compressed into tablet form. When this is done it impacts both magnesium stearate’s performance as a lubricant and the potential negative effects upon how a tablet dissolves.

The major beneficiaries of our research are the pharmaceutical industry. The ability to predict the properties of how magnesium stearate will perform in a formulation is crucial to making tablets reproducibly and avoiding potential product recalls. It will also speed up the development process by informing companies when their magnesium stearate supply changes, which can result in product delays.

Economic Impact:

Every pharmaceutical company seems to have a story where magnesium stearate caused a problem due to inconsistencies with suppliers or form changes that resulted in product failure. This breakthrough CPD research could have dramatic impacts on improving product quality through improved quantitative understandings of magnesium stearate’s functional properties and, more importantly, how variations impact product performance.

For more information, contact Eric Munson at the University of Kentucky,, Bio, 859.323.3107.