OBJECT DRUGS

Anticoagulants, Oral:

• Acenocoumarol
• Phenprocoumon
• Warfarin (Coumadin, etc.)

PRECIPITANT DRUGS

Absorption Inhibitors:

• Cholestyramine (Questran, etc.)
• Colestipol (Colestid)
• Sucralfate (Carafate)

Comment:

Bile acid binding resins and sucralfate bind with warfarin, phenprocoumon, and possibly other oral anticoagulants in the G.I. tract, thus reducing the anticoagulant absorption and response. Since warfarin and phenprocoumon undergo enterohepatic circulation, the binding cannot be completely avoided by spacing doses of the drugs.

Class 3: Assess Risk & Take Action if Necessary

• Circumvent/Minimize: Give oral anticoagulants 2 hours before or 6 hours after absorption inhibitors; keep constant interval between doses of oral anticoagulant and absorption inhibitor.
• Consider Alternative:Ezetimibe (Zetia) does not appear to affect the bioavailability of warfarin. The manufacturer found that colesevelam (WelChol) did not affect warfarin plasma concentrations, but they have received isolated reports of decreased INR when colesevelam was used with warfarin. More study is needed.
• Monitor: Monitor response to anticoagulant if absorption inhibitor is initiated, discontinued, changed in dosage or if the interval between doses of the oral anticoagulant and the absorption inhibitor is changed.