Magnesium stearate functions

Standards for dmg chemicals are pubUshed ia USP—NE. Dmg substances are chemicals that have therapeutic or diagnostic uses, whereas pharmaceutical iagredients provide preservative action, fiavoiing, or hilfillment of a function ia the formulation of dosage-form dmgs. Examples of dmg substances are acetaminophen [103-90-2] ampicillin [69-53-4] aspirin [50-78-2] powdered ipecac, riboflavin [83-88-5] staimous fluoride [7783-47-3] and thyroid. Examples of pharmaceutical iagredients are ethylparaben [120-47-8] lactose [63-42-3] magnesium stearate [557-04-0] sodium hydroxide [1310-73-2] starch [9005-25-8] and vanillin [121-33-5],... 

Fig. 12 Tensile strength of calcium sulfate tablets as a function of magnesium stearate concentration (solid fraction = 0.57). (From Ref. 29.)...

One very common beneficial interaction involving an excipient is the interaction between magnesium stearate and the metal of tablet punches and dies, or the equivalent parts on a powder encapsulation machine. Magnesium stearate is an example of a boundary lubricant. As such it has a polar head and a fatty acid tail. It is believed that the polar head of the magnesium stearate is oriented toward the die wall or tablet punch face. In these ways it is able to reduce the ejection force (the force required to eject the tablet from the die after compaction) and prevent sticking to the punch faces. The other boundary lubricants, e.g., calcium stearate and sodium stearyl fumarate, will also function in a similar manner. However, the so-called liquid film lubricants function in a very different manner (19). 

Since in this study in vitro dissolution served as the response or objective function for optimizing the level of magnesium stearate, it would appear that the authors of Ref. 8 had a high degree of confidence in this method. The dissolution test method and acceptance criterion in the selected example is fairly common. Its in vivo relevance is assumed by many with a fair degree of confidence, as exemplified by the following perspective expressed in the USP [35] ... 

It must be stressed that the functions of a glidant and lubricant in a tablet formulation are totally different. A few materials, e.g. talc, can act as both glidant and lubricant, but usually two different excipients are needed. Thus, although colloidal silicon dioxide is an excellent glidant, it has no lubricant activity. Conversely, magnesium stearate, despite its popularity as a lubricant, can hinder rather than promote flow. 

Emulsifiers and other functional ingredients, such as sodium or magnesium stearate, mono- and diglycerides, glycerol, polysorbates, and monostearates, can be derived from plant or animal sources. Products of animal origin may only be used if derived from kosher slaughtered beef animals etc. Therefore it is recommended to use synthetic products. 

Magnesium hydroxide filler treated with magnesium stearate has improved filler/matrix interaction and maleic anhydride functionalized EPR increased impact strength. The composition is very efficient in fire-retarded PP [20]. 

The surface modification of the fillers used is implemented by the use of a variety of chemical compounds such as organosilanes, stearic acid, fatty acid, silicone oil, zinc stearate, magnesium stearate, and titanium stearate. In this case, the modifier functional groups interact with the hydroxyl groups of filler, while the carbon chains of the modifier are much shorter than the carbon chains of the used polymer that hinders the... 

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