Automated In Vitro Dermal Absorption (AIVDA): A New In Vitro Method for Investigating Transdermal Flux
Richard P. Moody
A new in vitro method for investigating transdermal flux is described. The method, called Automated In Vitro Dermal Absorption (AIVDA), employed small autosampler vial inserts (Moody cells) to hold human skin (0.07cm2) in a standard autosampler carousel. HPLC was used to monitor the permeation rate of test compounds. Analysis was fully automated and remotely monitored and controlled via a modem. A modified Hank’s balanced salt solution was used to minimise HPLC background interference. Permeation assays conducted with Deep Woods®, a commercial N,N-diethyl-m-toluamide (DEET)-based mosquito repellent, showed no significant difference in DEET absorption between fresh and frozen human abdominal skin (Student’s t test [p ≤ 0.05] 56 ± 9.1% [n = 4] and 48 ± 6.3% [n = 4], respectively). No significant difference was obtained for DEET absorption in human skin pretreated with barrier cream. Preliminary tests conducted to validate AIVDA versus the standard Bronaugh procedure demonstrated excellent agreement for DEET permeation in rat skin (62 ± 12.8% [n = 4] Moody cells; 59 ± 8.1% [n = 3] Bronaugh cells). AIVDA has many advantages over other in vitro permeation tests, including automation, higher analytical sensitivity, rapid sample processing and the ability to use small (5mm outside diameter) skin specimens.