Investigation of drug release from suspension using FTIR-ATR technique: part I. Determination of effective diffusion coefficient of drugs

Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectros copy was used to study directly the release of drug particles (ketoconazole ) in a liquid medium (paraffinum liquidum). In the case of the release expe riment, the formulation is placed on the ATR crystal and the acceptor membr ane on the top of the ointment. The decrease of the drug content in the sed iment near the interface ATR crystal-formulation in the course of the relea se process was quantified by monitoring the changes of the IR spectrum in r elevant spectral ranges using multivariate analysis. A mathematical model b ased on Fick's second law with appropriate initial and boundary conditions was applied in order to determine the diffusion coefficient of the drug in the liquid medium. Knowing this value, it is possible to calculate the effe ctive diffusion coefficient of the drug in heterogeneous semisolid formulat ion (Vaseline) as a function of the volume fraction of the solid phase. (C) 1000 Elsevier Science B.V. Al rights reserved.