Quality Profile Evaluation of Topical Semi-Solid Systems with Ibuprofen ^†

The topical administration of non-steroidal anti-inflammatory drugs is described as an alternative route for inflammatory disease treatment and is frequently used because it determines local effects therapeutically, similar to oral administration, but with fewer side effects. The quality control of this type of product is not fully standardized due to technological particularities and the administration route. The aim of this study was to assess the quality profile of topical drug systems such as hydrogels with carbopol and ibuprofen [1,2].

Four hydrogels containing carbopol as gelling polymer and ibuprofen (5% and 10%, respectively) were tested. The hydrogels were evaluated in terms of macroscopic, rheological, and kinetic characteristics. The flow behavior was carried out using a rotational viscometer, at 33 °C and the rheograms, i.e., viscosity versus shear rate, were plotted. The analysis of ibuprofen release kinetics from the hydrogels was performed using two different approaches: Dynamic condition (modified Franz diffusion cell) and static condition (vertical diffusion cell—VDC) [3].

The hydrogels tested at 33 °C presented a non-Newtonian pseudoplastic behavior, the viscosity decreasing with the shear rate increase. The flow profiles were investigated by fitting the Power law model. The release tests in static conditions showed a faster diffusion of ibuprofen, and the release profiles indicated a constant phase after 240 min. On the other hand, the tests performed in a dynamic regime showed that the release of ibuprofen was slower and the constant phase was not reached after 480 min. The square root of time kinetic model fitted the ibuprofen release data, and the diffusion coefficient specific to the Higuchi model was determined [4].

The pseudoplastic behavior is a desirable property for topical systems, both in terms of conditioning and spreadability on the skin, and the formation of a continuous film at the application site. The VDC test is more discriminatory than the other one. For the samples that contain a higher concentration of ibuprofen, a little volume and a static regime of VDC can prevent maintaining sink conditions, and the dynamic method is preferred in this case [5].