Contribution to the Physical Stability Study of Compounded Medications Based on Zinc Oxide, Titanium Dioxide and Precipitated Sulfur Using Emulsified Solid Fats as Vehicles

Abstract

Marta Eugenia Porras Navarro and Jorge Andrés Pacheco Molina

Background: This investigation evaluated the physical stability of zinc oxide, precipitated sulfur and titanium dioxide suspensions using three solid fats as emulsified vehicles: stearyl alcohol, stearic acid and beeswax.

Method: Varying the concentration of solid fat (2%, 4%, 6%) and the agitation speed for the preparation of the emulsified vehicle (250, 500 and 750 rpm). Here 81 suspensions were prepared, 27 for each solid fat used. The apparent viscosity was measured using a Brookfield RVTD rotational viscometer. The selection of revolutions per minute and spindle used in the viscometer was carried out taking into account the need to obtain a reading in the instrument greater than 10.0, in accordance with the recommendation of the equipment manufacturer. The sediment volume was measured using identical graduated bottles.

Results: The effects that were studied as indicators of the physical stability of the suspensions were: sediment volume, apparent viscosity and ease of resuspension. This analysis indicated that the selection of the solid fat is a parameter significantly influential, which supports the data obtained through the investigation. Higher sediment volumes were obtained by increasing the concentration of the emulsified fat and increasing the speed of agitation, favoring thixotropic behavior in suspensions.

Conclusion: In terms of physical stability and ease of resuspension, the best results were obtained when emulsified stearyl alcohol was used as a vehicle.

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