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Abstract
A diffusion cell, termed the Patch Cell, suitable for conducting in vitro percutaneous absorption testing of transdermal nitroglycerine (TNG) delivery systems using skin from man, hairless mice and Yucatan pigs, is described. In addition, the Patch Cell can be utilized for batch-to-batch quality control testing of transdermal TNG delivery systems. The diffusion cell is incorporated into a laboratory robotics workstation that performs unattended, automated sampling of up to 24 diffusion cells over a 24-hour period. The method, referred to as the Patch Cell Method, has been used to measure the in vitro percutaneous absorption of TNG from two commercially available nitroglycerine delivery patches through hairless mouse skin, Yucatan pig skin, and human stratum corneum. TNG flux through hairless mouse skin, 30.2 +/-3.3 μg/cm2/hr from Transderm Nitro1 patches and 33.4 +/-8.2 μg/cm2/hr from Nitro Dur II2 patches, were comparable with the previously reported results of Keshary and Chien (9). The percutaneous TNG flux from these same patches, through the Yucatan pig skin, was 25.4 +/-2.4 and 21.9 +/-1.9 μg/cm2/hr respectively. TNG flux through human stratum corneum from Transderm Nitro patches was measured at 21.2 +/-4.1 μg/cm2/hr. The Patch Cell Method was also compared to the FDA dissolution bath technique for measuring percent drug released directly into saline, as a batch-to-batch quality control test. Results from the FDA and Patch Cell methods for three commercial nitroglycerine delivery systems were:
These results indicate that the Patch Cell method, in addition to being useful for in vitro percutaneous absorption assays, is also useful for direct release testing into water.