Abstract
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Monitoring of the coating end-point of functional coatings during the coating application process is desirable. Since currently available PAT methods require expensive test equipment, there is a need for a rapid test that can easily be applied without major investment. BARDS is a novel technique that has the potential to economise the production process of these kinds of pellet and tablet formulations. The thickness of a controlled release coating is a key factor that determines the release rate of the drug in the gastro-intestinal tract or other targeted functionalities such as taste masking or moisture protection. Correspondingly, the amount of drug per unit mass of pellets decreases with increasing thickness of the functional coating.
In this study, the functional polymer loading of the coating process is investigated by testing pellets via BARDS technology (Broadband Acoustic Resonance Dissolution Spectroscopy). The technique offers a rapid approach (<200 s) to characterising functional coatings at-line during their manufacture. Measurements are based on reproducible changes in the compressibility of a solvent during dissolution which is monitored acoustically via associated changes in the frequency of induced acoustic resonances. In case of enteric coatings a steady state acoustic lag time is associated with the erosion of the enteric coatings in acidic dissolution test media. This lag time is indicative of the coating layer thickness, assuming that the quality of the film coating is high. BARDS represents a possible future surrogate test for IPC testing, as a PAT method and possibly also for conventional USP dissolution testing. BARDS data correlate directly with the thickness of the functional coating, its integrity and also with the drug loading as validated by UV–Vis spectroscopy.