Effects of penetration enhancers on in vitro permeability of meloxicam gels

Meloxicam (MLX) was formulated as a 0.3% hydroxypropylcellulose (Klucel®) gel. The effect of four different combinations of co-solvents (ethanol, glycol-PEG-400, propylene glycol, and water) on MLX permeability was determined in vitro throughout isopropyl myristate (IPM)-saturated cellulose membranes. The gel consisting of 2.5% Klucel, propylene glycol, ethanol, and water (1:1:1) showed superior permeability properties and it was selected as the base-gel to investigate the effect of three levels of the penetration enhancers: dimethylsulfoxide (1, 5, and 10% DMSO), tween20 (1, 2, and 5% TW20), oleic acid (0.4, 1, and 5% OA), and menthol (1, 2.5, and 5% MT). In vitro permeability was determined throughout IPM-saturated cellulose membranes and human cadaver skin. DMSO and TW20 did not improve permeability of MLX compared to the control gel at any of the levels tested. Menthol produced a statistically significant (P < 0.001), dose proportional increase in MLX flux with a peak at 5% (2.43 ± 0.47 μg/cm2/h). Conversely, addition of OA peaked at 1% but decreased at the higher level (5%). There was no significant difference between the MLX amount recovered in stratum corneum and dermis across the different formulations tested. These findings show that the 0.3% MLX gel formulation containing 5% menthol can possibly deliver therapeutically relevant doses of MLX.