How long does Warfarin/Coumadin last?

[Barry]

Subject came up in another thread as an aside in a different context, didn't want to hijack the thread, so...

I'm given to understand that Coumadin has a pretty long half-life. So, for example, if I were to miss my dosing tomorrow there'd be no reason for me to lay awake tomorrow night worrying about getting a stroke. But...

Presuming you're starting with your INR in therapeutic range (3.5 for me, have an artificial mitral valve), how long can you go before you start coming to be at risk, and how rapidly does that risk increase over time?

More simply stated, while recognizing that there's individual differences, if I got stranded on a desert island without my meds, how long would it be before I might be in trouble and how long would it be before I assuredly would be in trouble?

 

[Ross]

Barry that's a hard one to answer because of the way people metabolize the drug. Some can miss a dose, like me, and fall below range in 24 hours. Others can go maybe 36, possibly 48, but I don't think that's a safe number to say. It just depends on the person involved.

 

[Barry]

Thanks, Ross. I've been on it for around three years and have yet to miss a dose. I'm actually pretty paranoid about it and carry an emergency stash in an airtight container on my key-ring in case I ever get stuck somewhere.

I hope I never get busted for anything. I used to do mental health work in a county jail, and at least that jail wouldn't give you any meds you happened to have on you when you got busted. They'd call your doc and dispense only on his or her prescription - which could take a day or two.

 

[lance]

Warfarin 1/2 life of 4 days

Warfarin 1/2 life of 4 days

Anticoagulation therapist told me warfarin ans a half life of 4 days and then tapers off. Not sure how this applies to individual differences.

 

[Barry]

Barry's right - if you happen to end up in the pokey for whatever reason, they won't dispense to you anything that was on your "person" when you came in, even if it's something you need to stay alive....

I'm finding myself thinking that it might be a good idea next time I see the doc to ask him to write a prescription that I can keep on my person for such an eventuality. Same with my Beta Blockers because I've read that it's dangerous to cold-turkey off of those. Those of you saying to yourself that you don't need to worry about it because you're a law-abiding citizen, you need to remember that law-abiding citizens get busted sometimes, too. Nobody's perfect, including cops. That's why we have courts.

 

[Guest]

The half life of warfarin varies according to what variation of the metabolizing enzymes that you have in your body. If you take 10 mg, it will probably drop below range if you miss one dose. If you take 1 mg per day it may take 4 days. The average is about 2 days to have the INR drop to 1/2 of what it was. If you miss 4 days, it is almost certainly as if you had never taken it at all.

RCB went years without warfarin because he was one of the first valve replacement people to survive longer than 30 days. They had no idea whether he needed it or not. Some people stroke out after missing 2 days for a colonoscopy.

There are lots of variables so that nobody knows for sure how long it will take before you stroke or (the good news) merely wreck your valve.

All of the variables are also why I believe that it is impossible to say that Coumadin is better than generic. For more than 1/2 of the times that the INR is out of range, the reason cannot be found.

I will be giving a presentation next month at the Anticoagulation Forum (about 800 warfarin specialists from all over the world). I will be presenting the idea that idone is the reason for the unpredictability. Iodine affects the thyroid and the thyroid affects the INR. For instance, there is more iodine in drinking water at sea level than in the mountains. It is just possible that this is why people find that their INR is out of range when they go on vacations or maybe weeks after they return from vacation. Iodine acts slowly and is in many products such as table salt and Robitussin cough syrup which we are told does not affect the INR. Maybe it does but the effect is seen weeks after you take it and nobody suspects. We have had this drug for 50 years and there is something that affects that we have not recognized yet. It has to be something that can make a small, slow change.

 

[perkicar]

How long to get therapeutic?

How long to get therapeutic?

I'm curious....I'm a nurse and have recently had a patient who was in recovering from surgery for breast cancer. She has an artificial mitral valve due to rheumatic fever many years ago. They let her INR get to 1.1 post surgery, then she came back in with a hematoma at her surgery site.

To anticoagulate her they put her on lovenox BID and her home dose of coumadin (which was 6.25 and 7.5 alternating days). Her INR went up to 1.4 then stopped changing. Should they have put her on a heparin drip to quickly anticoagulate her? I overheard one of the oncologists talking and said there was only a 1% chance of forming a clot on that valve (and that seemed way under estimating to me).

Just curious as to others experiences getting anticoagulated....And how it's normally done. Both for my own reference post surgery and if I have other patients in the future. They didn't get the cardiology team involved until yesterday.

Also, the patient is a Jehovah's witness and will not take any blood products. Could her low hemoglobin (less than 6) have anything to do with her INR not rising???

 

[Guest]

It is a tough call when someone has a hematoma. I've seen some pretty sick mechanical valve people with post-op hematomas, that got infected. You pretty much have to take care of the acute bleeding and hope for the best with the clotting. These people tend to have bad outcomes. However, one of my patients who was in a very bad way in January is now healthy again. The doc wanted his INR checked every day and he was so weak that he could barely get to the clinic. It is the only time I have ever done this, but I showed his wife how to use the CoaguChek, loaned her one of my spares and the supplies and gave them my cell phone number so that she could call the results to me on the weekend.

Low hemoglobin probably did not play a role. HgB and clotting are two different mechanisms.

 

[perkicar]

It is a tough call when someone has a hematoma. I've seen some pretty sick mechanical valve people with post-op hematomas, that got infected. You pretty much have to take care of the acute bleeding and hope for the best with the clotting. These people tend to have bad outcomes. However, one of my patients who was in a very bad way in January is now healthy again. The doc wanted his INR checked every day and he was so weak that he could barely get to the clinic. It is the only time I have ever done this, but I showed his wife how to use the CoaguChek, loaned her one of my spares and the supplies and gave them my cell phone number so that she could call the results to me on the weekend.

Low hemoglobin probably did not play a role. HgB and clotting are two different mechanisms.

It's an interesting case for us as health care providers. I'm betting she would improve significantly if we could just give her 4 or 5 units of PRBC. But we have to respect her beliefs. Her HgB had at least stabilized as of yesterday. But she felt pretty crappy, and the family was very concerned. I'm hoping she'll pull through this one.