INR

  My Mitral valve was replaced (Carbomedics) at the Cleveland Clinic Florida in late January. I was discharged in 4 days and had a very easy quick recovery. On coumadin, my INR had been running 2.5 to 3.1 untill 3 days ago when I found blood (a lot) in my urine. My doctor prescribed another PT, urine specimin, and complete blood count. Diagnosis was an infection in my prostate and an INR of 10 (ten). My question: Is it possible to go from 3 to 10 in three weeks with no diet change? The only possibilty I can think of, is the addition of 50 mg per day of Atenolol for blood pressure, 3 or 4 days before this problem began. By the way, I stopped the Atenolol.
  Thank You

[Cleveland Clinic, MD]

Dear Robert,
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.  Common reasons for coumadin use are in atrial fibrillation to reduce the risk of stroke, in persons with clotting disorders, in persons with mechanical heart valves, and sometimes in people with severe heart failure.  The usual dosage is somewhere between 1 and 15 mg a day.  Potential side effects include bleeding, hair loss, nausea, vomiting, stomach cramps, diarrhea and leukopenia (low blood cell count).  The half life (amount of time for half the drug to be cleared from the body is 42 hours but varies widely depending on the individual).  
Many drugs interact with coumadin and may cause more anticoagulation effect (clofibrate, diazoxide, ethacrynic acid, nalidixic acid, phenylbutazone, salicylates, aspirin, sulfonamides, alcohol, allopurinol, amiodarone, cimetidind, phenytoin, erythromycin, gemfibrozil, propranolol, thyroid drugs) or decreased anticoagulation effect (smoking, estrogens, vitamin K, aluminum hydroxide - antiacids, cholestipol, spironolactone).  See complete list below.  The effects of coumadin must be carefully monitored by a blood test called an INR.  Usually this is checked more often at the onset of taking the drug and less often once a steady state has been reached.  Therapeutic INR is usually 2 to 3 depending on the condition being treated.
Pregnant women and those with a hypersensitivity to coumadin should not take this medication.  
The medication should not be taken with food and any signs of bleeding should be reported to your doctor.  Use a soft toothbrush, avoid hazardous activities, carry Medi-Alert ID identifying drug useage and notify your doctor if you have any dark brown urine or red or tarry black stools.
Known Drug interactions with Warfarin
Increased Effect :
                       Highly Probable
                            Alcohol (if concomitant liver disease)
                            Amiodarone
                            Cimetadine
                            Clofibrate
                            Cotrimoxazole
                            Erythromycin
                            Fluconazole
                            Isoniazid
                            Metronidazole
                            Miconazole
                            Omeprazole
                            Phenylbutazone
                            Piroxicam
                            Propafenone
                            Propanolol
                            Sulfinpyrazone
                       Probable
                            Acetaminophen (Tylenol