Diffusion of nitroglycerin from drug delivery patches through micro-fibre filters using Fourier transform infrared photoacoustic spectrometry

In this paper, the diffusion of the angina therapeutic agent, nitroglycerin through a skin mimetic is described. The mimetic is a poly(ethylene) glycol loaded microfibre filter to which a transdermal drug patch is attached. The diffusion process is monitored using dynamic scanning Fourier transform infrared (FTIR)-photoacoustic spectrometry in which the IR beam illuminates the filter with the transdermal patch on the underside. Thus, the nitroglycerin diffuses up through the filter. Using different thermal diffusion lengths, as determined by the wavelength dependent modulation frequency of the FTIR spectrometer, the diffusion process is monitored. A convenient model is developed to provide a direct measurement of the diffusion coefficient of nitroglycerin through the poly(ethylene) glycol loaded filter.