Changes in digoxin pharmacokinetics associated with hepatic P-glycoprotein upregulation in rats with non-alcoholic fatty liver disease

Upregulation of hepatic P-glycoprotein (P-gp) expression has been reported in patients with non-alcoholic fatty liver disease (NAFLD) and rodent models thereof. Here, we explored the changes hepatic P-gp expression and activity in a NAFLD rat model and the effects thereof on the pharmacokinetics of digoxin (a probe substrate of P-gp).

Rats were fed a 1% (w/w) orotic acid-containing diet for 20 days to induce NAFLD; control rats received a normal diet. P-gp expression and biliary digoxin excretion were examined. The pharmacokinetics of digoxin were evaluated after it had been administered intravenously (10 μg·kg^-1 ) and orally (200 μg·kg^-1 ) to control and NAFLD rats.

The total areas under the plasma concentration-time curves (AUCs) of digoxin after intravenous and oral administration were significantly smaller (by 39.1% and 73.0%, respectively) in NAFLD rats because of faster biliary digoxin excretion, reflecting elevations of hepatic P-gp expression and activity. Notably, the steady-state volume of distribution rose by 98.2%, while extent of oral bioavailability fell by 55.5% in NAFLD rats.

This is the first study to report digoxin pharmacokinetic changes caused by hepatic P-gp upregulation in NAFLD. Further studies are needed to explore the clinical impact of enhanced P-gp-mediated biliary excretion on pharmacotherapies using P-gp substrates in patients with NAFLD.