In vitro release studies of piroxicam from oil-in-water creams and hydroalcoholic gel topical formulations.

The importance of piroxicam, a therapeutic anti-inflammatory drug, is well known. Because of gastrointestinal disorders, dermatological dosage forms are recommended most. In our first studies, oil-in-water (O/W) creams of piroxicam (1% concentration) were prepared using glyceryl monostearate (GMS), stearic acid, and triethanolamine as additive ingredients. In our second studies, hydroalcoholic transparent gel formulations of this drug in a 0.5% concentration were prepared using hydroxypropylcellulose (HPC) as the gelling agent. The release of piroxicam from all formulations via dialysis through a cellulose membrane into phosphate buffer pH 6.8 at 37 degrees C was studied. The effects of additives such as propylene glycol and 2-propanol on the drug release were also investigated. The release profiles from the standpoint of diffusion-controlled processes, as well as zero-order and first-order kinetics, were evaluated, and relevant parameters, such as diffusion coefficient, permeability coefficient, and partition coefficient, were calculated. The release obeys both the diffusion mechanism and first-order kinetics. The drug release from gel formulations containing 10%, 20%, and 30% propylene glycol was decreased due to the enhancement of viscosity. However, the limpidity of these formulations was improved. Moreover, the release of drug from gel formulations containing 15% and 20% of 2-propanol was increased. These results show that a hydroalcoholic gel formulation with HPC is a more suitable preparation of piroxicam when compared with an O/W cream formulation.