SPI Pharma’s Barcroft™ Resuspendable Magnesium Hydroxide Powder (RMP) is a unique version of magnesium hydroxide powder. It is special in its ability to be resuspended, thereby forming a pharmaceutically elegant Milk of Magnesia suspension.

When processed correctly, suspensions made from Barcroft™ RMP allow users to reduce or eliminate the use gum additives and suspending agents which are normally employed when attempting to suspend a fine powder.

Milk of Magnesia is typically prepared from a 7 to 10% RMP in water mixture. It is characteristic of an RMP suspension to Ross Laboratory High Shear Mixer gain viscosity as it is subjected to shear. But a maximum viscosity is reached beyond which additional mixing time will actually cause the material to thin out.

Many users have the notion that the longer the suspension is mixed, the better will be the product quality. An important parameter that can guide milk of magnesia manufacturers is particle size. At a mean particle size of 8 to 11 microns, the solution is expected to be at its thickest. This viscosity plateau will vary from one user to another but is supposed to be greater than 1,000 cps.

The behavior of RMP solutions prepared on a plant scale is expected to parallel laboratory results. But because shear is more a consequence of tip speed rather than rotor speed in rpm, optimum mixing speed in larger high shear mixer models may vary from the findings of the bench top experiments.

In consideration of the differences in formulation and other processing conditions, it is recommended for RMP users to plot their own viscosity and particle size profiles. Knowing these important data and using the proper high shear mixer will enable Milk of Magnesia manufacturers to benefit most from Barcroft™ RMP’s unique properties, cut costs, and optimize processing time.

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