Magnesium stearate tablet lubricant

Benzalkonium chloride Preservative Magnesium stearate Tablet lubricant... 

Fig. 16 Effect of lubricant on dissolution of rate of salicylic acid contained in compressed tablets, x, 3% magnesium stearate , no lubricant 0> 3% sodium lauryl sulfate. (From Ref. 21.).

NIR was used to determine the effects of changes in magnesium stearate concentration and variations in compression pressure on tablet analysis. Various types of Avicel (microcrystalline cellulose), varying mostly in particle size, were compressed into tablets with or without magnesium stearate as lubricant by using various compression pressures. Various mathematical treatments were used to either measure the differences or obviate their effects on the analysis. 

The main details of the formulation and the limits of the experimental domain were given in table 10.8. Other components not noted in the table were the drug substance (1 - 2%) and a lubricant (magnesium stearate). Tablets at 6 mg were made by direct compression of the mixture. The concentration of drug substance (a soluble salt) were allowed to vary between 1% and 2%. Thus, the domain shown in figure 10.7 may be considered as being repeated for each concentration of drug substance tested. 

Ghdants are needed to faciUtate the flow of granulation from the hopper. Lubricants ensure the release of the compressed mass from the punch surfaces and the release/ejection of the tablet from the die. Combinations of siUcas, com starch, talc (qv), magnesium stearate, and high molecular weight poly(ethylene glycols) are used. Most lubricants are hydrophobic and may slow down disintegration and dmg dissolution. 

Other studies have been performed to investigate the effect of surface area and tablet lubricant efficacy. In a comparison study between sodium stearyl fumarate and magnesium stearate, it was found that sodium stearyl fumarate was effective as a lubricant to about the same degree as magnesium stearate [15]. It was also reported that the lubricating properties correlated better to the surface area of the lubricant than to the amount of lubricant used. A micronized lubricant was more efficient than a coarse fraction, and it was suggested that the surface area be standardized to obtain reproducible effects. 

Lubricant Prevents powder/tablets sticking Stearic add, magnesium stearate, sodium... 

Lubricants are used in tablet preparation and include magnesium stearate, stearic acid and polyethylene glycol. They only comprise at most 1-2% of the tablet bulk so that their potential to interfere is slight, particularly since their chromophores are weak. The fatty acid lubricants can often be observed if analysis of a tablet extract is carried out by GC-FID. Tablet coatings are often based on modified sugar polymers such as hydroxypropylmethylcellulose. These coatings are used at about 3% of the tablet bulk, are water soluble and do not absorb UV light. 

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). 

A tablet formulation is a complex system that contains the drug substance, usually a hydrophilic Lllersuch as lactose, a disintegrant such as cornstarch, a lubricant such as magnesium stearate, and maybe a Low-regulating excipient such as silicium dioxide (A sliilnfortunately, the quality... 

Lubricants act by interposing an intermediate layer between the tablet constituents and the die wall, to prevent adherence of the granules to the punch faces and dies. Thus, they ensure smooth ejection of the tablet from the die. In addition, many lubricants also enhance the flow properties of the granules. Stearic acid and its magnesium and calcium salts are widely used. The most effective lubricants, such as magnesium stearate, are very hydrophobic and can also prevent wetting of powders and hence retard dissolution (Figure 6.9). 

Magnesium stearate - used as a lubricant in tablet formulations. 

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