Conclusions
CL gel (0.016%) and ointment were inequivalent, with an optimized release profile, suggesting minimal passage of CL gel through human epidermal tissue to the dermis.
Methods
Release profiles of CL from the gel and a compounded ointment-based 0.016% CL formulation were compared via in vitro release testing (IVRT), utilizing static diffusion cells, a pseudo-infinite dose, and polytetrafluoroethylene membranes, over 5 h. The percutaneous absorption profile of CL gel in ex vivo human skin was also examined, using in vitro permeation testing (IVPT) with flow-through diffusion cells, dermatomed skin (epidermis plus dermis) and epidermal membranes, a finite dose, over 24 h.
Results
In IVRT experiments, the mean ± SD CL release rate was significantly higher for the gel versus the ointment (5.70 ± 0.73 versus 2.38 ± 1.03 μg/cm2/√h); the formulations were inequivalent per the US Food and Drug Administration scale-up and postapproval changes for nonsterile semisolid dosage forms (FDA SUPAC-SS) criteria. Mean IVPT cumulative CL (gel) permeating through epidermal membrane was higher than for dermatomed skin (4.6% versus 2.5% of applied dose). Mean residual CL on the epidermal membrane surface was 1.3% of the applied dose. Conclusions: CL gel (0.016%) and ointment were inequivalent, with an optimized release profile, suggesting minimal passage of CL gel through human epidermal tissue to the dermis.