I ve been taking coumadin for about 4 months now, along with prednisone and plaquenil for my SLE. I was wondering if second-hand smoking (both from cigarettes and marijuana) affect the results my medicine gives since some friends I hang out with smoke frequently.
Hello, While second-hand smoke can affect your health, especially your lungs, it should not significantly affect the medications you are taking.  Smoking can also increase the risk for blood clotting, which would work against the Coumadin you are taking, but I doubt second-hand smoke would have any major effect. Hope I have answered your query. Let me know if I can assist you further. Take care Chat Doctor.