Fourier transform Raman microscopic study of drug distribution in a transdermal drug delivery device

The mapping facility of a Fourier transform Raman microscope was used to construct a profile of oestradiol distribution in a transdermal drug delivery device (Hormone Replacement Therapy patch). Mapping was performed across a region of the patch which contained crystallised material for characterisation, The spectra acquired using the microscope facility were compared with those obtained of pure oestradiol and of pure oestradiol recrystallised from ethanol. The spectra clearly show the solid inclusions to be oestradiol, and that there is an increase in oestradiol concentration in the neighbourhood of the crystal; it was concluded that the drug had crystallised in the patch at some stage during the manufacturing process. The results demonstrate the value of the mapping facility in characterising and determining the homogeneity of components in a complex system.