where Papp is obtained in cm/s, QA(t) is the amount of compound at the time t in the acceptor well, VD is the volume in the donor well, t is time in seconds, A is the area of the membrane in cm and QD(t0) is the amount of compound in the donor compartment at the beginning of the experiment. Statistical analysis: unpaired two-tailed student t tests were applied to evaluate the significant difference or p values between data sets using Prism 6.0c software.