Estimation of drug excretion rate from blood into the gut using a three-compartment closed model.

After administration and absorption, some drugs can be excreted via various mechanisms from blood into the gut; the determination of this drug excretion rate may have important clinical and pharmaceutical implications. A three-compartment closed model with first-order absorption was designed using absorption, blood and eliminated compartments to estimate the drug transfer rate from blood into the gut. Theoretically, the excretion rates of drugs whose blood concentrations can be described by the one-compartment open model with first-order absorption can be estimated using the developed model. This theoretical deduction was supported by 100 Monte Carlo simulations performed in the present study. A sensitivity analysis suggests that the estimated drug transfer rate from blood into gut is very sensitive to blood drug concentrations. Meanwhile, an example also shows the limitation of the developed model.