INR Yo-yo (Warfarin)

[Stample]

It took ages for my INR levels to reach a baseline and now it seems to be see-sawing between my therapeutic range and much lower.

The goal is 3.5 (between 3 and 4). I have gone from 3.5 to 2.1 to 3.5 to 2.6 over the last few weeks.

I can't seem to figure this out, originally when it dipped they thought it was because I stopped taking all pain meds.

Any advice from other users in keeping it stable ?

[ILowe]

Hi. presume these INR figures are for when you do NOT change the dosage, do not miss a dose, and do not do any boosting?

Let me tell you a medical secret that the medical profession will not face up to. In some people (myself included) there can be a wide variation in INR for no obvious reason. It usually auto-corrects. Intervention only makes the swings worse. [Reference 1]. Before the medical profession became fixated on narrow target ranges of 1.0 INR, they should have done some big studies over many years (>1000 people followed over at least 10 years) of people who had very little intervention, in order to find out what the characteristics of the natural biological variation. If you can find such data, please let me know. The studies have not been done. It would probably be considered unethical to do them since patients are left at extremes, and doing nothing can get you into more trouble than doing something. Evidence from self-dosers though is ethical, but would be hard to collect in sufficient numbers and detail.

Frustrated with this, as a self-doser aiming at an INR >3 (metallic heart valve) with data going back over 25 years I looked for and found swings. One of them was from 2.4 to 4.8 and back again, all without changing anything. My body autocorrected. For details see Reference 2.

Then there is the problem that the medical profession seem to delight to act quickly, though fortunately there is a limited literature suggesting that waiting is legitimate. Reference 3.

Why are there extremes? I think there are three main ones, in order of probability:

1/ Chance

2/ Change in the reservoir level

3/ Change in the input=output

Most times, Chance needs to be given time to act, afterall, dropping to 2.5 or increasing up to 5 or so is not dangerous.

If it is not chance, then the reservoir level probably needs adjusting. This is done by stepping ie a minor xtra dose for a few days to increase the level, or a minor cut for a few days to reduce the level.

Only once reasons 1/ and 2/ are covered, I am tempted to adjust the actual dose, and then I do it with a very small change, perhaps as low as 0.25mg. I have found this small dose to be more significant than diet (though I may be a special case). I hope this helps.

Reference 1. Meier DJ, Seva S, Fay WP 2007 A comparison of anticoagulation results of patients managed with narrow vs. standard international normalized ratio target ranges. compared narrow and wider target ranges J Thromb Haemost 5:1332-4

They found that the tight control led to more swings, but failed to link their findings to the possibility that they could be due narrow targets being against nature. In addition, they failed to question and take into account the validity of the testing; narrow target ranges of 0.5 are a priori rendered impossible given the current state of the art of measurement.

Reference 2. Lowe I. 2017. Warfarin self-dosing, a case study on long term self-management of anticoagulation. Journal of Observation Pain Medicine Vol 6 pp 31-40. joopm.com

Reference 3. Schulman S1, Melinyshyn A, Ennis D, Rudd-Scott L. Single-dose adjustment versus no adjustment of warfarin in stably anticoagulated patients with an occasional international normalized ratio (INR) out of range. Thromb Res. 2010 May;125(5):393-7. doi: 10.1016/j.thromres.2009.07.006. Epub 2009 Jul 29.

[Stample in reply to ILowe]

Thank you for such a thorough response.

I am currently taking 8.5mg of warfarin. My last self test today was 2.9. I am next at the clinic on Thursday so will see how it is then. I have not missed a dose and nothing has changed. When it was 2.3 the nurse did up the warfarin from 8 to 8.5.

I think I'm trying to figure out how dangerous it is for me with a mechanical valve to have an INR below 3 and above 4. At what levels should I be worrying?

Thanks again for your input, as this is for life now understanding it as much as I can will put my mind at ease.

[ILowe in reply to Stample]

I think I feel like you. I like to know what is going on. I like to make up my own mind. Bland assurances only make me nervous. OK. Here goes.

1/ Basic protection kicks in at around 2.0

2/ There is a margin of error for even venous blood which is variously estimated at 5-15%. In practice, you want to keep above 2.5 to factor in this MoE.

3/ You can safely go up to 5.0 without any real danger

So that means you are aiming to keep between 3-4, and are watchful on either side.

Swings must be avoided, since once started they can get worse. You dampen swings by ignoring them (hence Reference 3 above) or by very slight changes.. stepping.

I regard getting too low far riskier than going high. As sailors know, there is room for error out at sea, the margins get broader at higher levels of INR. So, I am more likely to act when i have a low result than when I have a high result.

When I act, I initially try stepping. Dose change is a last resort. So if I had been your nurse I would have said 8.5mg for three days, then back to 8mg. If that failed, I would have tried 8.5mg for three days then 8.25mg.

There is another element to be aware of. The INR system is more sensitive at higher levels of INR. This means that increasing a low INR requires a greater dose change than decreasing a high INR.

Now, given that I know the natural biological variation is >2, and that any figure from 2.5 to 5.0ish is safe, I am not too worried. I also know that intervention can make things worse.

[Semley]

I used to take warfarin for many years and got on pretty well with it but during a routine visit with my consultant he remarked that if I were a new patient he would recommend one of the new warfarin substitutes which would not require regular checks. I agreed to change to apixaban and have had no problems since. I don't know if that would be a possible solution for you.

[Stample in reply to Semley]

Thanks Semley but from my understanding the alternatives are not suitable for mechanical valves.

I have my checkup tomorrow.