Studies regarding the in vitro release mechanism and rheological properties of piroxicam from hydrophilic gel formulations

Abstract

Introduction: Piroxicam is one of the most used and prescribed drug for the treatment of inflammatory diseases. When administered topically, piroxicam is a better therapeutic alternative to the systemic way because of its local effects and an improved release on affected tissues, with a low incidence of systemic side effects. As a hydrogel, piroxicam ensures a good compliance of the patient and a very good therapeutic effect at the same time. This paper evaluates the topical release systems of piroxicam from hydrogels formulated with sodium carboxymethylcellulose, following its kinetic and rheological properties. Methods: In vitro release studies of piroxicam from hydrogels were carried out using a modified Franz diffusion cell fitted with a synthetic membrane (in this case, cellophane). Rheological measurements were performed at two different temperatures, using a rotational viscometer Multi-Vise Fungilab, equipped with standard spindles by recording the shear stress at different speeds in ascending and then descending order Results: The release data analyzed by the Higuchi equation provided the highest correlation coefficients. The flow curves which followed the Herschel-Bulkley model revealed a non-newtonian shear thinning behaviour. Conclusion: The effectiveness of piroxicam released from hydrogels and the rheological characteristics are strongly influenced by the formulation properties as viscosity agents and the concentration of its components. Thus, the kinetic and rheological profiles can be modulated by the formulations factors in order to obtain the optimal drug amount released at the application site.