In vitro dermal absorption of carfentanil

There is growing concern regarding potential occupational exposures to the ultra-potent synthetic opioid carfentanil. However, little data are available on the toxicity of carfentanil in humans, particularly for dermal exposures. To begin to address this, permeation of carfentanil formulated in three vehicles, water, ethanol, and hand sanitizer was measured under infinite-dose conditions in an in vitro static diffusion cell system using the EpiDerm™ (EPI-606-X) RhE model. The permeation rate was fastest for carfentanil in water (3.9 × 10^-3 cm/h), followed by hand sanitizer (1.2 × 10^-3 cm/h), and slowest for carfentanil in ethanol (0.2 × 10^-3 cm/h). In both ethanol and hand sanitizer, a lag-time between exposure and permeation of approximately 1.5 h was observed, while lag-time in water was approximately half an hour. Flux at steady-state was greater at 50.6 μg/ml than at 5.3 μg/ml for both water and ethanol; however, the percent of dose absorbed did not differ between doses for either vehicle. Slight differences in percutaneous permeation of carfentanil were observed between two brands of hand sanitizer, likely due to differences in relative proportion of alcohol and skin penetration enhancers. These data indicate that small skin exposures may not result in rapid, significant toxicity as previously reported.