Drug Interactions

[Robbyn]

I am trying with still great difficulty to keep my INR at a safe level. I had surgery Feb. 2004 and still need to go each week to have it checked. One week it is 2.4 and the next week it is 5.7. I believe the culprit that week was ginger tea. The pharmacist said I could take for nausea.

I guess my question is for Al. I have just started taking Methotrexate today for vasculitis (microscopic polyangitiis) and I see a warning for an interaction with Coumadin. Could you tell me what to expect this time?

Thanks again for all the info on the sigmoidoscopy. Everything worked our perfect. And thanks for any info on this matter.

 

[Guest]

I see a lot of people who take methotrexate and don't recall ever seeing an interaction. I can't find anything that details anything specific. There was a theoretical article published in 1990, so the warning may be based on that.

I think a more likely culprit than ginger tea is the reason you were taking the ginger tea - nausea. Also the sigmoidoscopy comes into play. Any time that anything happens that throws off the normal bacteria in your intestine, you can expect to have an elevated INR. The 5.7 INR is about what I would expect to see if you have gone through these two things recently.

My bet would be that the person monitoring your INR cut the dose by a rather hefty amount as a result of the 5.7. This means that you can expect a low INR next time. If you were my patient and had a sigmoidoscopy that gave normal results recently and the nausea is resolving, I would have held one dose and had you take the same warfarin dose for another week and rechecked you in about 10 days.

If you are a year post-op and still having your INR checked every week, I don't think that the person dosing your warfarin has very much of an idea as to what they are doing. Unless you have antiphospholipid antibody syndrome there is no excuse for not having the warafrin dose adjusted so that you only need monthly testing by this time.