Lubrication of Direct-Compressible Blends with Magnesium Stearate Monohydrate and Dihydrate - Pharmaceutical Technology

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Lubrication of Direct-Compressible Blends with Magnesium Stearate Monohydrate and Dihydrate
The influence of magnesium stearate (MgSt) on powder lubrication and finished solid-dose properties presents big challenges to drug manufacturers.

Pharmaceutical Technology


Figure 12
Magnesium stearate is currently available commercially as the monohydrate form or a mixture of monohydrate with a trace of amorphous and other hydrate forms made from both animal and vegetable fatty acid sources. The isolation of pure magnesium dihydrate form has provided a neat dihydrate form with distinct physicochemical properties from the monohydrate form (10).

Figure 13
Physicochemical analysis conducted with scanning electron microscopy, powder X-ray diffraction, near-infrared spectroscopy, differential scanning calorimetry, particle-size analysis, and thermogravimetry suggest discernable differences between MgSt monohydrate and dihydrate.

Figure 14
The lubrication of direct-compressible blends with the hydrates of MgSt has presented evidence of differences in the effects these hydrates could have on blend homogeneity and tablet compression. In-line effusivity sensors predicted blend uniformity in all prelubrication blends down to 1.25% w/w of active pharmaceutical ingredient in the formulations. In addition, the in-line effusivity sensors suggested that lubricating blends with the monohydrate form could cause greater disturbance in blend particlearrangement and densification than the dihydrate form under similar process conditions.

Table X: f2 comparison for MCC–DCP–APAP tablets with different MgSt types.
Finally, compression results showed that blends lubricated with MgSt-M required higher total-compression forces, ejection force, and knock-off force than those with MgSt-D. Similarity comparison based on the f2 factor, as conducted on finished products, indicates that the blends lubricated with MgSt-D compared well with those containing MgSt-M.


The authors express gratitude to Dr. Nancy Mathis and Michael Emanuel of Mathis Instruments, Doug Kirsch and Dale Natoli of Natoli Engineering Co., Mike Kelly, Dr. Gary Nichols, Samantha Compton, Dan Ramlose, and Don Krieger of Mallinckrodt, and Dr. John Kaufman of the US Food and Drug Administration in St. Louis for their valuable discussion and contributions to this work.

Patrick Okoye is a quality manager at OSG/Kolmar Laboratories, Port Jervis, NY. Stephen H. Wu, PhD,* is a technical fellow in the Pharmaceutical R&D division of Mallinckrodt Pharmaceutical–Covidien Ltd., 385 Marshall Ave. Webster Groves, MO 63119, tel. 314.654.0281,

*To whom all correspondence should be addressed.

Submitted Feb. 13, 2007. Accepted:Mar. 14, 2007.


1. M. Turkoglu, I. Sahin, and T. San, "Evaluation of Hexagonal Boron Nitride as a New Tablet Lubricant," J. Pharm. Dev. Technol. 10 (3), 381–388 (2005).

2. P. Okoye et al., "Thermal Effusivity Blend Lubrication Data as a PAT Platform to Optimize Tablet Compression Performance," AAPS Poster #T3195 (2005).


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