Delay effect of magnesium stearate on tablet dissolution in acidic medium

Area of Science:

• Pharmaceutical Science
• Materials Science

Background:

• Magnesium stearate (Mg-St) is a widely used lubricant in solid pharmaceutical formulations.
• Mg-St is known to impede the dissolution rate of tablets.

Purpose of the Study:

• To elucidate the mechanism by which Mg-St delays tablet dissolution.
• To investigate the influence of acidic environments on Mg-St mediated dissolution delay.

Main Methods:

• Stationary disk method for dissolution testing.
• Scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) for surface analysis.
• Fourier transform infrared spectroscopy (FTIR) for chemical identification.

Main Results:

• Mg-St accumulates on the tablet surface during dissolution, limiting drug release via diffusion.
• The generation of stearic acid from Mg-St was observed in acidic dissolution media.
• Stearic acid, being less soluble than Mg-St, contributes to a slower dissolution rate in acidic compared to neutral conditions.

Conclusions:

• The dissolution delay caused by Mg-St is primarily a diffusion-controlled process.
• The formation of stearic acid in acidic media significantly enhances the dissolution retarding effect of Mg-St.