Dear Pharma Friends,
It is quiet sometime after I reach you all through this important and useful topic .
Do you face erratic drug dissolution in your tablets formulation
Wonder what could be the reason? Do you
Remain clueless?
True,
Even a simple formulations of dry granulation types are no exception
To these type of issues.
Irony is even in those formulation where product as such itself more fragile due to insufficient binding but still when it comes for drug release in the disso medium the test fail
Why? Who is the culprit,
Well one of the reason is higher proportion
Of lubricants especially magnesium stearate
Magnesium stearate is an additive that is most frequently used as a lubricant. Magnesium stearate is capable of forming films on other tablet excipients during prolonged mixing, leading to a prolonged drug liberation time, a decrease in hardness, and an increase in disintegration time. It is hydrophobic, and there are many reports in the literature concerning its adverse effect on dissolution rates also.
magnesium stearate added in formulation (concentration 1,1%), being hydro-phobic in nature, forms a stronger film at the surface of other excipients or the API . In that manner, it enables the dissolution medium to remain on the surface of the particle causing slower wettability, and dissolution rate as well.
Readers for your reference find below
A research article elucidating the implication of adding Magnesium stearate and dissolution.
Delay effect of magnesium stearate on tablet dissolution in acidic medium
Abstract
Magnesium stearate (Mg-St) is a common lubricant used for solid pharmaceutical formulations and is known for its property to cause delay of tablet dissolution. In this study, the mechanism underlying the delay caused by Mg-St was investigated with model metformin hydrochloride (HCl) tablets containing Mg-St by using the stationary disk method, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). The results revealed the process and mechanism of delay: the exposed amount of Mg-St on the tablet surface increases during the dissolution process and tablet dissolution is limited by the diffusion of Mg-St. Also, in the case of dissolution in acidic medium, stearic acid derived from Mg-St was detected on the tablet surface by FTIR.
Because the solubility of stearic acid is lower than that of Mg-St, the slower dissolution in acidic medium than in neutral medium may be attributed to the generation of stearic acid
.
The purity of MgSt (ratio of stearic and palmitic acid) may affect its lubrication efficiency. The delay in the dissolution of a highly soluble drug was more pronounced in the presence of commercial MgSt (pharmaceutical grade mixture of stearic and palmitic salts with not less than 40% of stearic acid) compared with high purity MgSt (> 90% of stearic acid)
The slower drug dissolution was attributed to the formation of an extensive hydrophobic layer The purity of MgSt (ratio of stearic and palmitic acid) may affect its lubrication efficiency. The delay in the dissolution of a highly soluble drug (paracetamol, United States Pharmacopeia (USP) 2 apparatus, 0.1 N HCl pH 1, 25 rpm, 37°C) was more pronounced in the presence of commercial MgSt (pharmaceutical grade mixture of stearic and palmitic salts with not less than 40% of stearic acid) compared with high purity MgSt (> 90% of stearic acid) [9]. The slower drug dissolution was attributed to the formation of an extensive hydrophobic layer around particles by commercial compared with high purity must. The formation of the hydrophobic layer around particles by MgSt depends on the solid-state form of the excipient.
Conclusion:
So it is clear from the above that though the need for using magnesium stearate is quite indispensable for forming good tablets
Without any physical defects but
The most crucial point to be considered in its usage are,
1.usage of the material inappropriate
Quantities and
2. lesser mixing time in blenders.
3.Increasing the surface area of lubricant material by sieving through Higher mesh size to ensure uniformity in it's mixing at the lesser mixing time.
Deviating from the above could fail drug release within the stipulated period.
See you all in my next article till then,
Cheers,
Srikanth Santhanaraman
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