Release of Poorly Soluble Drugs from HPMC Tablets Studied by FTIR Imaging and Flow-Through Dissolution Tests

Chemical imaging of the stratum corneum under controlled humidity with the attenuated total reflection Fourier transform infrared spectroscopy method

Attenuated total reflection Fourier transform infrared spectroscopic imaging was applied to study human stratum corneum (SC) tissue, the outermost layer of the skin. This imaging approach was combined with a controlled environment cell to demonstrate the possibility of obtaining chemical images of SC exposed to a wide range of relative humidities and diffusion of ethanol through the SC tissue with a specially designed liquid cell. The effect of water vapor sorbed into the SC on the distribution of other components in the SC was studied. Principal component analysis was applied in conjunction with univariate analysis to differentiate the distribution of different components in the SC. Swelling of the SC, a heterogeneous distribution of natural moisturizing factor and water, was detected upon the increase of relative humidity. The approach to image the penetration of liquid ethanol into the SC was also demonstrated and showed good potential and implications for studying transdermal drug delivery.

Predicting the drug concentration in starch acetate matrix tablets from ATR-FTIR spectra using multi-way methods

The amounts of drug and excipient were predicted from ATR-FTIR spectra using two multi-way modelling techniques, parallel factor analysis (PARAFAC) and multi-linear partial least squares (N-PLS). Data matrices consisted of dissolved and undissolved parallel samples having different drug content and spectra, which were collected at axially cut surface of the flat-faced matrix tablets. Spectra were recorded comprehensively at different points on the axially cut surface of the tablet. The sample drug concentrations varied between 2 and 16% v/v. The multi-way methods together with ATR-FTIR spectra seemed to represent an applicable method for the determination of drug and excipient distribution in a tablet during the release process. The N-PLS calibration method was more robust for accurate quantification of the amount of components in the sample whereas the PARAFAC model provided approximate relative amounts of components.

Applications of ATR-FTIR spectroscopic imaging to biomedical samples

FTIR spectroscopic imaging in ATR (Attenuated Total Reflection) mode is a powerful tool for studying biomedical samples. This paper summarises recent advances in the applications of ATR-FTIR imaging to dissolution of pharmaceutical formulations and drug release. The use of two different ATR accessories to obtain chemical images of formulations in contact with water as a function of time is demonstrated. The innovative use of the diamond ATR accessory allowed in situ imaging of tablet compaction and dissolution. ATR-FTIR imaging was also applied to obtain images of the surface of skin and the spatial distribution of protein and lipid rich domains was obtained. Chemical images of cross-section of rabbit aorta were obtained using a diamond ATR accessory and the possibility of in situ imaging of arterial samples in contact with aqueous solution was demonstrated for the first time. This experiment opens an opportunity to image arterial samples in contact with solutions containing drug molecules. This approach may help in understanding the mechanisms of treatment of atherosclerosis.