Bioequivalence is a vital concern in drug development and is even more significant in case of drugs that have narrow therapeutic index. The in vitro dissolution testing is a useful tool for forecasting the in vivo performance of drug products and potentially reduces the number of bioavailability / bioequivalence (BA/BE) studies required. In case of drug products that have low systemic absorption, in vitro binding studies are considered as an acceptable alternative to BA/BE studies by regulators including USFDA for classifying the equivalence.