What affects INR

[jarno1973]

I am trying to find good info on how INR is affected:

Most things I now have a bit of an idea about. Some are still not clear though:

Dehydration is said to affect INR. Information on internet I found was contradicting. Does anyone know if it will go up or down?

How will antibiotics normally affect INR?

I found increased exercise will decrease the INR. Is this correct and why is this? Does this also have something to do with exercise and related dehydration?


Hope someone has experiences to share...

Regards,

Jarno

 

[JimL]

Dehydration is said to affect INR. Information on internet I found was contradicting. Does anyone know if it will go up or down?

Never thought about that.

How will antibiotics normally affect INR?

Normally, either up or down in my experience, but not much. Not much help, I know.

I found increased exercise will decrease the INR. Is this correct and why is this? Does this also have something to do with exercise and related dehydration?

The extra exercise speeds up your metabolism, that is, your processing of the coumadin. The faster you process it through your system, the sooner it is gone, and then INR decreases. I generally need to increase my dosage in the spring, and decrease it in the fall, due to the change in physical activity.

 

[dick0236]

I agree with JimL I have had antibiotics take my INR up, down, or no change, depending on the type of antibiotic....although antibiotics seldom have a dramatic effect on my INR. Increased activity and exercise does have some effect on my INR, although I seldom, if ever, have to change my short term(daily) dose . I would suspect that dehydration would lower INR, similar to the effect of exercise. Over many years on warfarin, my dosage has decreased from about 70mg/wk to the current 35mg/wk. I am reasonably certain that this delcine has a lot to do with my sedentary, retired lifestyle now.....as compared with my earlier "young mans" active life and lifestyle....and the decrease in dosage has been very gradual. The only times that my INR has had dramatic swings has been due to Rx interactions......last time was with a statin.

 

[Protimenow]

I'm bringing up the advice that you've probably seen here in many places -- whatever you do, try to be consistent. Yes, antibiotics can have an effect on your INR. So do diet and activity.

Until recently, we've been cautioned against eating too many greens or other sources of Vitamin K because it lowers your INR. More recent (and enlightened) thinking is that your body NEEDS Vitamin K for things other than anticoagulation, and it's been noted that keeping a consistent intake of K can actually help you to stabilize your INR.

My advice -- get a meter if you don't already have one. Test weekly (if you can afford the strips), or more often if you've made any major changes to your routine (started a new medication, drastically increased or decreased activity, made dietary changes, etc.) consider testing even more often.

For many of us, the $5 or so per strip is worth much less than the peace of mind that frequent testing - if needed - can provide. I'm NOT advocating making dosage adjustments just because your INR changes a bit -- too much modification can start the INR roller coaster.

I think that we're still learning about all the stuff that can make your INR change -- and some of this may have to do with your age, and maybe even your genetics.

 

[chaconne]

At this point, It doesn't seem like anything affects my INR. For the first 2-3 Months post AVR, it kept dropping and my dose increased. Now Ive been stable for 2 months and it doesn't seem to matter what I eat or how I exercise, though I guess these could be considered regular by some.

 

[Protimenow]

Chaconne -- it's easy to assume that, if you aren't tested often enough and just happen to be tested when the INR is at a certain level - that your INR is stable. If I check my clock every 12 hours exactly, it's also very stable. Personally, I like to test once a week (although, since I'm running low on strips, I'm pushing that out until I can afford more or find someone with expired InRatio strips that I can get inexpensively). Personally, I think everyone who is able to perform a self test SHOULD be able to -- whether they can manage their own dosages or have a doctor or clinic do this -- but having the ability to do your own test will, at the very least, save you the expense and hassle of going to a clinic or lab for testing.

Do you have your own meter? Do you do your own testing? How do you know that your INR REALLY IS stable if your testing is at 2, 3, or more weeks from the previous test?

 

[Bill B]

I've not come across any evidence that exercise affects warfarin metabolism or response. Warfarin is metabolized by an enzyme system in the liver called cytochrome P-450. MANY drugs are metabolized by the same system or a subset of it. Skeletal muscle metabolism and liver enzyme metabolic rate are unrelated. If you ask people who think that exercise affects their INR, you will get some who report it goes up, some down and other unchanged. That's because it's not related.

Some drugs are so effectively cleared by the liver that liver blood flow does affect their elimination. Warfarin is not one of them.

 

[TheGymGuy]

Bill, I am bookmarking this post. A very interesting perspective. I am going to do some research on warfarin metabolizing and exercise effect on it. Hopefully, EL will show up before long with some links.

 

[chaconne]

Chaconne -- it's easy to assume that, if you aren't tested often enough and just happen to be tested when the INR is at a certain level - that your INR is stable. If I check my clock every 12 hours exactly, it's also very stable. Personally, I like to test once a week (although, since I'm running low on strips, I'm pushing that out until I can afford more or find someone with expired InRatio strips that I can get inexpensively). Personally, I think everyone who is able to perform a self test SHOULD be able to -- whether they can manage their own dosages or have a doctor or clinic do this -- but having the ability to do your own test will, at the very least, save you the expense and hassle of going to a clinic or lab for testing.

Yes, I understand your perspective. We certainly have discussed this issue before. I should have qualified my statements by saying "according to my clinic, I've been stable...". From my discussions with them, they seem to be more concerned with the overall stability, rather than worrying about dips and crests in INR.

 

[Eva]

Since my surgery, ONLY one time my INR kept decreasing for a while which baffled me, until I realized my new calcium pills contained Vit. K. My INR stabilized again once I stopped them. I could have adjusted my dosage and continued taking them, but I chose to switch to another brand.

 

[Cris N]

One other thing that I notice and Hemosense (now Alere) reported anecdotal evidence is that when the weather gets hot, my INR goes up.