In vitro diffusion cell design and validation. II. Temperature, agitation and membrane effects on betamethasone 17-valerate permeation.

An in vitro permeation cell has been designed and validated for use in monitoring the transmembrane permeation of betamethasone 17-valerate. The design utilizes common laboratory equipment and incorporates as many beneficial features as possible from other designs. The importance of fully validating the hydrodynamic performance of the cell prior to experimentation is stressed. The cell was validated by monitoring the diffusion of betamethasone 17-valerate in isopropyl myristate solution into purified isopropyl myristate receptor phase at different temperatures, different agitation rates and through different synthetic and biological membranes. The results of the hydrodynamic validation agree with data from other researchers and show that the permeation cell is adequately sensitive to these experimental parameters. The results of the membrane evaluation allow appropriate selection of the barrier material for representative transdermal experiments to be conducted. While human and porcine stratum corneum/epidermis are similar in diffusive properties, hairless mouse skin appears to be the most convenient animal membrane for these studies. Although silicone and cellulose membranes appear to be useful in this application, porous filter membranes and egg-shell membranes are insufficiently discriminatory to betamethasone 17-valerate diffusion to provide useful in vitro permeation data.