Transporters in the human liver play a major role in the clearance of endo- and 
xenobiotics. Apical (canalicular) transporters extrude compounds to the bile, 
while basolateral hepatocyte transporters promote the uptake of, or expel, 
various compounds from/into the venous blood stream. In the present work we have 
examined the in vitro interactions of some key repurposed drugs advocated to 
treat COVID-19 (lopinavir, ritonavir, ivermectin, remdesivir and favipiravir), 
with the key drug transporters of hepatocytes. These transporters included 
ABCB11/BSEP, ABCC2/MRP2, and SLC47A1/MATE1 in the canalicular membrane, as well 
as ABCC3/MRP3, ABCC4/MRP4, SLC22A1/OCT1, SLCO1B1/OATP1B1, SLCO1B3/OATP1B3, and 
SLC10A1/NTCP, residing in the basolateral membrane. Lopinavir and ritonavir in 
low micromolar concentrations inhibited BSEP and MATE1 exporters, as well as 
OATP1B1/1B3 uptake transporters. Ritonavir had a similar inhibitory pattern, 
also inhibiting OCT1. Remdesivir strongly inhibited MRP4, OATP1B1/1B3, MATE1 and 
OCT1. Favipiravir had no significant effect on any of these transporters. Since 
both general drug metabolism and drug-induced liver toxicity are strongly 
dependent on the functioning of these transporters, the various interactions 
reported here may have important clinical relevance in the drug treatment of 
this viral disease and the existing co-morbidities.