Lopinavir: acute exposure inhibits P-glycoprotein; extended exposure induces P-glycoprotein.

The effect of lopinavir on P-glycoprotein-mediated rhodamine 123 efflux was studied in Caco-2 monolayer cells. Lopinavir is a potent inhibitor of Rh123 efflux in Caco-2 monolayers (IC50 1.7 microM). Chronic lopinavir exposure (72 h) in LS 180V cells reduced the content of intracellular Rh123 by approximately 50%, indicating increased efflux activity. In LS 180V cells, lopinavir induced P-glycoprotein immunoreactive protein (up to threefold) and messenger RNA levels in a concentration-dependent fashion.