Influence of sorption of polydimethylsiloxane on the determination of its content in tablet mixtures

Introduction. Excipients with sorption properties are used in pharmacy as carriers, glidants, stabilizers, thickeners. However, their use is limited by potentially incomplete desorption of active pharmaceutical ingredients (API), which can affect quantification of API. Accuracy of determining the content of polydimethylsiloxane (PDMS), which is main component of simethicone, is significantly depends on drug matrix.

Objective: to investigate sorption of PDMS in tablets containing simethicone and magaldrate. Evaluate the contribution of individual components of tablet mixture (TM) to degree of sorption.

Material and methods. TM of different composition were analyzed. The quantitative content of PDMS in TM was determined by gel permeation chromatography with refractometric detector.

Results. The different grades of magaldrate, probably differing in the ratio of amorphous and crystalline phases, exhibit different sorption activity to PDMS. The granulation of magaldrate with hypromelose reduce sorption of PDMS on the antacid. The most significant sorption of PDMS was observed in presence of silicon dioxide (SD). While complete desorption of PDMS did not occur. Direct relationship has been established between the amount of SD and the amount of sorbed PDMS.

Conclusion. We found that the main reason for decrease in degree of transition of PDMS into solution from simethicone and magaldrate TM is sorption of the polymer by antacid and SD. In case of magaldrate, we chose the conditions that allow complete desorption of polymer. While the similar structure of PDMS and SD, covalent and noncovalent interactions leads to partial chemisorption of PDMS and, consequently, its incomplete desorption.