I am taking oral azathioprine and Coumadin. I have been told to increase my dosage to 150 mg. daily. Since doing so my taking of Coumadin , my INR , protine, has been 1.5-1.6. It should be in the 2.00-3.00 range. I have increased , dosage of Coumadin to 7.5 mg. 3/week, and 5 mg. daily. I was also taking mycophenolate till recently. Can the increased dose of azathioprine be diminishing the effect,of the Coumadin. I am taking Coumadin ,for Atrial Fibrilation