Use of high doses in patients on warfarin (monitor INR) & w/ liver failure. Patients w/ many lesions that have tendency to bleed (eg, bleeding peptic ulcers), history of hemorrhagic stroke & inherited bleeding disorders (eg, hemophilia). Stop high dose supplementation 1 mth prior to surgery. Pregnancy & lactation.
May antagonize effect of vit K. May result in hemorrhage w/ anticoagulants eg, warfarins. High doses may potentiate effect of antiplatelets (eg, aspirin, clopidogrel, ticlopidine) & herbs w/ antithrombotic activity (eg, garlic & gingko). May enhance side effects of amiodarone, ciclosporin & zidovudine. May reduce requirement for digoxin &/or insulin. Absorption may be decreased w/ orlistat. Absorption/utilization may be interfered w/ colestyramine, colestipol, INH, mineral oil, neomycin & sucralfate. Plasma levels may be lowered w/ anticonvulsants (eg, phenobarb, phenytoin, carbamazepine) &/or OCs. Antioxidative effect may be decreased w/ dietary fiber supplementation.
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