Near infrared spectroscopy to monitor drug release in-situ during dissolution tests

Dissolution tests can be used to demonstrate suitable in vivo drug release through in vivo/in vitro correlations. This work explores the possibility of using near infrared spectroscopy (NIRS) to monitor in-situ dissolution tests. It aims at expanding surrogate methods in quality control of drug products. Laboratory designed tablets of an immediate-release formulation containing folic acid and four excipients were used as case study. The dissolution tests were performed on a 1L vessel filled with 500ml of Milli-Q water with a rotating paddle apparatus (apparatus 2, Ph. Eur.) at 50rpm and 37±0.5°C. Near infrared (NIR) spectra were acquired in-situ with a transflectance probe connected to a Fourier-transform near infrared spectrometer. NIR spectra were regressed against folic acid concentration by partial least squares (PLS) regression. Folic acid concentrations during dissolution tests were obtained by periodically sampling the dissolution vessel and resourcing to an UV method. The proposed real-time NIR method was tested on a validation run yielding a root mean squared error of 0.25μgml^-1 (0.16μgml^-1 for the calibration runs) and a R² of 0.93 (0.95 for the calibration runs). The results suggest that NIRS is a suitable analytical technique for monitoring in-situ dissolution tests.