Dose staggering as a strategy to reduce drug-drug interactions due to reversible enzyme inhibition between orally administered drugs with high first pass effect: A computer simulation study

A physiological computer model was designed to simulate the metabolic. drug -drug interactions between two orally co-administered drugs due to reversib le enzyme inhibition using drug concentrations in the portal vein. The exte nt of interactions was compared at steady-state for the effects of a delay in time between the administration of the substrate and the inhibitor. It w as demonstrated that the extent of the interactions can be strongly affecte d by a time interval between the two drug administrations. By delaying the administration of the inhibitor until after the absorption phase of the sub strate, one can significantly reduce the extent of the drug-drug interactio ns. This is because drug concentrations in the portal vein and the liver ar e much higher than that in the systemic circulation during the absorption p hase. The model also showed that interactions involving substrates with a h igh extraction ratio (E-H), i.e., drugs with higher first-pass effect, can be more strongly affected by dose staggering. Substrates with a low absorpt ion rate constant (k(a)) require a longer interval with the inhibitor in or der to reduce the extent of the interactions. This observation suggests dos e staggering as a simple and cost-effective way to reduce the extent of unw anted drug-drug interactions in clinical practice. Copyright (C) 2000 John Wiley & Sons, Ltd.