Piroxicam delivery into human stratum corneum in vivo: iontophoresis versus passive diffusion.

A nonsteroidal anti-inflammatory drug, piroxicam, was administered from a commercially available gel to human volunteers both passively and under the application of an iontophoretic current. The effect of occlusion on the passive delivery of piroxicam was also examined in a separate series of experiments. After treatment, the stratum corneum (SC) at the site of application was progressively tape-stripped and piroxicam transport into the membrane was assessed by UV-analysis of drug extracted from the tape-strips. Analysis of variance did not show any significant difference between passive piroxicam delivery after 30, 60 or 125 min. However, current application enhanced drug uptake into the SC, as indicated by both increased piroxicam concentrations in the horny layer and detectable concentrations at greater depths into the membrane. The total amount of drug recovered in the SC post-iontophoresis was significantly higher than that found following passive diffusion for each application time. The amounts of drug recovered from the tapes after 60 and 125 min of current application were significantly higher than that after 30 min treatment. Finally, the in vivo SC concentration profiles following passive delivery were fitted to the appropriate solution of Fick's second law of diffusion to determine skin partitioning and diffusivity parameters.