Digoxin is not a Substrate for OATP1A2, OATP1B1, OATP1B3, and OATP2B1

September 13, 2011

New SOLVO Article has been published

Digoxin is not a Substrate for Organic Anion Transporting Polypeptide Transporters OATP1A2, OATP1B1, OATP1B3, and OATP2B1 but is a Substrate for a Sodium Dependent Transporter Expressed in HEK293 Cells Drug Metab Dispos. 2011 Aug 17. [Epub ahead of print] Digoxin, an orally administered cardiac glycoside cardiovascular drug, has a narrow therapeutic window. Circulating digoxin levels (Cmax ~1.5 ng/mL) require careful monitoring, and the potential for drug-drug interactions (DDI) is a concern. Increases in digoxin plasma exposure caused by inhibition of P-glycoprotein (P-gp) have been reported. Digoxin has also been described as a substrate of various organic anion transporting polypeptide (OATP) transporters, posing a risk that inhibition of OATPs may result in a clinically relevant DDI similar to what has been observed for P-gp. While studies in rats have shown that Oatps contribute to the disposition of digoxin, the role of OATPs in the disposition of digoxin in humans has not been clearly defined. Using two methods, Boehringer-Ingelheim, GlaxoSmithKline, Pfizer, and Solvo observed that digoxin is not a substrate of OATPs 1A2, 1B1, 1B3 and 2B1. However, digoxin inhibited the uptake of probe substrates of OATP1B1 (IC50 of 47 μM), OATP1B3 (IC50 > 8.1 μM), and OATP2B1 (IC50 > 300 μM), but not OATP1A2 in transfected cell lines. Interestingly, digoxin is a substrate of a sodium dependent transporter endogenously expressed in HEK293 cells, as uptake of digoxin was significantly greater in cells incubated with sodium-fortified media compared to incubations conducted in media where sodium was absent. Thus, while digoxin is not a substrate for the human OATP transporters evaluated in this study, in addition to P-gp mediated efflux, its uptake and pharmacokinetic disposition may be partially facilitated by a sodium-dependent transporter. Find out more about the publication Check out the full list of peer-reviewed drug transporter publications

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