Increased risk of serious GI tract bleeding w/ oral anticoagulant therapy eg, acenocoumarol, anisindione, dicumarol. GI irritation w/ alendronate. May decrease antihypertensive & natriuretic effect of ACE inhibitors particularly in low renin hypertensive patients. Reduced plasma conc, peak plasma levels & AUC values w/ aspirin. Increased BP & interference w/ BP control w/ β-adrenergic blockers. Increased risk of GI hemorrhage w/ Ca channel blockers eg, felodipine. May antagonize antihypertensive effects of Ca channel blockers. Decreased absorption w/ cholestyramine. Elevated liver transaminases w/ comfrey & germander. Increased cyclosporine levels, nephrotoxicity & plasma creatinine conc. Increased digoxin serum conc. May enhance anticoagulation w/ eptifibatide. Increased risk of hepatotoxicity w/ eucalyptus. May predispose patient to more adverse effects (eg, gastropathy, increased risk of bleeding & nephropathy) w/ feverfew. Inhibited platelet aggregation or coagulation w/ gingko. May cause tissue congestion, mucosal sloughing & necrosis, & intestinal wall hemorrhage w/ gossypol.