It is possible for jumps in the INR to occur and this is why careful monitoring is important. Atenolol may interact with coumadin (generic warfarin). Common foods such as grapefruit
juice, leafy green vegetables and many drugs can also change coumadin levels. Smoking also changes drug levels.
The following is information on warfarin and it's drug interactions.
Coumadin (generic name Warfarin) is a anticoagulant (blood thinner) that is used for a variety of conditions.