In vitro release, rheological, and stability studies of mefenamic acid coprecipitates in topical formulations

Abstract

A suitable topical formulation of mefenamic acid was developed in order to eliminate the gastrointestinal disorders associated with its oral administration. Drug coprecipitates prepared with different polymers at various drug-to-polymer ratios improved drug solubility and dissolution compared to pure drug and physical mixtures. PVP polymers (ratio 1:4) produced the best results. Aqueous ionic cream, ointments of absorption and water soluble bases and gels of methylcellulose, carboxymethylcellulose sodium, HPMC, Carbopol^® 934 and 940, and Pluronic^® F127 bases containing 1–10% drug as coprecipitates of PVP polymers (1:4) were prepared. The highest drug release was achieved at 1% drug concentration from water soluble base and methylcellulose among cream/ointment and gel bases, respectively. Gels, in general yielded better release than creams/ointments. All tested medicated creams/ointments exhibited plastic flow while all gels conformed to pseudoplasticity. Most of them showed thixotropy, a desired property of topical preparations. Stability studies revealed that HPMC and methylcellulose had the smallest changes in drug content, viscosity, and pH among the formulations. Considering drug release, rheological properties, and stability, methylcellulose gel containing 1% drug as coprecipitates of PVP K90 was the best among the studied formulations, was promising for improving bioavailability of mefenamic acid and can be used in future studies.

Keywords::

• Mefenamic acid
• topical
• coprecipitates
• PVP K90
• gel
• methylcellulose

Acknowledgments

The authors like to thank Dr Kristopher Virga of Irma Lerma Rangel College of Pharmacy of Texas A&M University Health Science Center for his useful contribution in explaining the drug releasing behavior of the formulations.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.