Abstract

OBJECTIVES:

The effects of the flavonoid rutin on the anticoagulant activity of oral warfarin and the protein binding and pharmacokinetics of its enantiomers were investigated in rats.

METHODS:

A single dose of racemic warfarin, 1.5 mg/kg, was administered orally to rats either alone or on day 5 of an 8-day oral regimen of rutin, 1 g/kg daily.

RESULTS:

Rutin reduced the anticoagulant effect of racemic warfarin, evident as a 31% reduction in the area under the prothrombin complex activty-time curve (P < 0.05).

KEY FINDINGS:

Rutin had no apparent effect on pre-treatment baseline blood coagulation. It enhanced the in-vitro serum protein binding of S- and R-warfarin (reflected by 40% and 26% reductions in unbound fraction, respectively), and thus restricted distribution by 33 and 21%, respectively. Treatment with rutin significantly decreased the elimination half-life of S-warfarin by 37% as a result of the 69% increase in unbound clearance of the S-enantiomer. This effect was attributed to a significant 77% increase in the unbound formation clearance of the overall oxidative and reductive metabolites, and an increase in the unbound renal clearance of the more potent S-enantiomer of warfarin.

CONCLUSIONS:

Concurrent rutin administration is likely to reduce the anticoagulant effect of racemic warfarin, reflecting a significant decrease in the elimination half-life of the more potent S-enantiomer.