warfarin dosage levels

[pellicle]

Hi

forgive me if this is covered elsewhere, but after visiting my dentist recently I became interested (again) in what my warfarin dose is like (compared to others).

Clearly there are many variables (I have a background years ago in a BSc in Biochemistry but have never worked in medical fields) and so I'm only wondering about ball park figures here.

I currently take 7.25mg of (Marevan) daily (in reality its 7.5 alternating with 7) to keep my INR between 2.8 and 2.2 (which is what my surgeon recommends for the therapeutic range). I have an ATS valve (don't know more details of that) which is one of the modern carbon types comparable to the On-X valve.

I weigh about 74Kg (163 or so pounds, not a clue how to get that into stones sorry).

Does this seem like a 'median' dose to others or is this 'high' to get my desired (as I understand it lowish) INR?

thanks

 

[Freddie]

Hello there and Welcome to the forums.
74Kg = 160 lbs
74Kg = 11.65 Stones

Most of us here use lbs and Kg, not sure who uses Stones.

To answer you question: each of us metabolizes warfarin differently. So you stay with the dosage that works best for you.

 

[dick0236]

Hi

I weigh about 74Kg (163 or so pounds, not a clue how to get that into stones sorry).

Does this seem like a 'median' dose to others or is this 'high' to get my desired (as I understand it lowish) INR?

thanks

Your activities in your profile would indicate that your lifestyle may metabolize warfarin more quickly. 7.5mg/day could be a normal dose for an active 47 year old. I am 165lbs and normally take 5mg/day, but I am also 76 and not nearly as active as you probably are. There is no "standard dose" for warfarin, but activity level and exercise will have an effect on the warfarin needed to maintain INR.

 

[dwhist]

Well for comparison, I am 200 pounds and extremly active having biked 3000 miles this year. I usually do at least 1 hour of working out each evening if not on bike for 1 1/2 hours. At this time I take 30 mg a week, 5 mg 5 nights a week and 2.5 the other 2 days, which seems low to me. I am uaually in the 2.5 to 3.0 range. I do eat all the greens I want.

 

[KristyW]

Pellicle,

There doesn't seem to be any correlation between body size and warfarin dosage. Both my husband and I are on warfarin, he's 58 years old, 6'4" tall, 265 lbs and takes 22mg of warfarin per week (3 mg x 6, 4 mg x1), he fabricates custom cars and is on his feet all day, up and down on the shop floor, and back and forth to his tool box.

I'm 50 years old, 5'4", 150 lbs and have a fairly sedentary job, but I take 42 mg of warfarin per week.

The dose you take is the dose that's right for your body/metabolism.

 

[newmitral]

I was also curious about the average dose of warfarin it takes for folks to stay within their target range and did some research on the topic a while ago. The first thing to recognize is that "it takes what it takes" and the result is more important than the dose itself.

I have found a few references that give this type of information, two of which are listed below. There are genetic markers that have been found to help determine whether a given person will be more or less resistant/sensitive to warfarin. The "median" dose required to stay within the target range is about 5.0 mg/day (35mg/week) from the papers I could find. Figure 2 in reference #1 below is a nice plot of the dose distribution.

My own dose required to stay in range is 12.5mg/day (87.5mg/week) which is certainly a three-sigma case on the high dosage side, but it just takes that much for me. I'm a reasonably active male, not particularly overweight (although I could stand to lose about 10 pounds). Weight doesn't seem to be a factor for my dosage, since it took the same 12.5mg/day dose to get in range right after my valve replacement when I was still very thin and about 30 lbs underweight. I don't eat a lot of greens, or other vitamin-k containing foods (although I do eat what I want to eat and "dose the diet"), so I'm assuming that I must have genes that make me somewhat warfarin resistant. But I don't worry about it, I just take the dose required to keep me in range.

References:

1. "Individualizing Warfarin Therapy" (Reynolds, Valdes, Hartung & Linder) - Future Medicine -2007
(see figure-2 in this paper for the graph referred to above)

2. "Warfarin Pharmacogenomics" (Jiayi Li, MD; Shan Wang, PharmD, RPh; Joseph Barone, PharmD Candidate;
and Brian Malone, MS, RPh) Pharmacy & Therapeutics Journal - August 2009

I don't have web links handy, since I downloaded copies of these papers some time ago, but you can google for them to read the original articles.

 

[pellicle]

so I'm assuming that I must have genes that make me somewhat warfarin resistant. But I don't worry about it, I just take the dose required to keep me in range.

Yes, that's about the conclusion I was reaching. Since it is essentially a type of toxin T's the bodies resistance to the limited toxicity that seems to vary.

Thanks for those references too

 

[pellicle]

Thank you everyone for your valuable inputs

 

[Bina]

My body is super sensitive to any med that I take......Coumadin included.....I take 16 mg per WEEK.
(small woman, lightweight) inactive.

 

[Jkm7]

My neighbor is super sensitive to coumadin. Her range is 2.0 - 3.0, she is about 70 years old, 160 pounds and takes a total of about 9 or 10 mg per week. She takes 1 mg most days and 1.5 a few days each week.

 

[TheGymGuy]

I was also curious about the average dose of warfarin it takes for folks to stay within their target range and did some research on the topic a while ago. The first thing to recognize is that "it takes what it takes" and the result is more important than the dose itself.

I have found a few references that give this type of information, two of which are listed below. There are genetic markers that have been found to help determine whether a given person will be more or less resistant/sensitive to warfarin. The "median" dose required to stay within the target range is about 5.0 mg/day (35mg/week) from the papers I could find. Figure 2 in reference #1 below is a nice plot of the dose distribution.

My own dose required to stay in range is 12.5mg/day (87.5mg/week) which is certainly a three-sigma case on the high dosage side, but it just takes that much for me. I'm a reasonably active male, not particularly overweight (although I could stand to lose about 10 pounds). Weight doesn't seem to be a factor for my dosage, since it took the same 12.5mg/day dose to get in range right after my valve replacement when I was still very thin and about 30 lbs underweight. I don't eat a lot of greens, or other vitamin-k containing foods (although I do eat what I want to eat and "dose the diet"), so I'm assuming that I must have genes that make me somewhat warfarin resistant. But I don't worry about it, I just take the dose required to keep me in range.

References:

1. "Individualizing Warfarin Therapy" (Reynolds, Valdes, Hartung & Linder) - Future Medicine -2007
(see figure-2 in this paper for the graph referred to above)

2. "Warfarin Pharmacogenomics" (Jiayi Li, MD; Shan Wang, PharmD, RPh; Joseph Barone, PharmD Candidate;
and Brian Malone, MS, RPh) Pharmacy & Therapeutics Journal - August 2009

I don't have web links handy, since I downloaded copies of these papers some time ago, but you can google for them to read the original articles.

Thanks for references. Now, I have some more reading material to feast my eyes on. For reference for others at this time I weight around 195lbs, at 5'8"and exercise lots as most of you know. I take 10mg daily for a total of 70mg / week. It took me at least 3-4 month to get stable, we started at 2mg per day after OHS and jumped slowly to 10mg, until I was stable in the mid 2s.
In addition I consume Vit. K in the AM and PM with at least one serving of greens per day.

 

[vivekd]

My doctors are trying to keep my INR in the 2.5 - 3.0 range, but it does not seem to be working. I always have been hyper active, gym rat with really high metabolism. My INR went down from 2.4 to 1.8 last week and have been advised to bump my warfarin to 15 mg / day. It seems that as I increase my activity level, i need more and more warfarin.

I run 3 miles during my cardic rehab session (3 times / week).
Run 5 miles on Saturday keeping my heart rate between 160-165
Walk 6-8 miles during rest of the days.

We're still trying to figure out correct dosage. My nurse told me that they'll allow me to self manage after 90 days, so I would have to wait for 25 more days.

 

[TheGymGuy]

VivekD, as my exercise varies I find that my INR varies a little bit too. Diet seems to have little effect, body weight does, and activity does for me.
Even when my INR varies it is within 1.8-3.5 INR (and this is over a 4 year sample size of weekly testing and constant coumadin intake). The only difference that you and I might have is that I take a sports all-in-one multi-vitamin in the AM and PM (12 hours apart) that has vitamin K in it to keep my vitamin K buffers stables.

Your INR seems to be stabilizing and once it gets in the consistent range you will be good to go. Since you are only 3 months out of surgery you might still need a month or two to get things in perfect control. If you can try to test weekly using home testing kits.

Best,
GymGuy

 

[Agian]

Vivek, I've got an On-X. They told me to aim for an INR of 2-3. Different surgeons, I guess.

Gym Guy, how much Vitamin K do you take? Does it affect your INR? Vitamin K was topical a little while ago here.

 

[pellicle]

Hi

My doctors are trying to keep my INR in the 2.5 - 3.0 range, but it does not seem to be working.

well that is a narrow range, and I don't think its practicable to steer for that. I think you should target 2.5 and accept anything between 2.0 and 3.0 as being A-Ok

having said that I agree with TheGymGuy that its still early days and the dose will be adjusting as you heal and your metabolism changes / settles.

I always have been hyper active, gym rat with really high metabolism. My INR went down from 2.4 to 1.8 last week and have been advised to bump my warfarin to 15 mg / day. It seems that as I increase my activity level, i need more and more warfarin.

its a reaosnable conclusion, although myself (using my garmin) the last years worth of weekly readings have not found a very strong correlation between activity (determined by active KCal) and my INR. True a correlation exists, but its not strong.

We're still trying to figure out correct dosage. My nurse told me that they'll allow me to self manage after 90 days, so I would have to wait for 25 more days.

well (as I'm sure you know) data is the answer ... myself (with none of yours to observe) I'd speculate that the problems are; they have not been giving you a consistent dose per day, they have been altering your dose in response to observations and making bad calls. If you wanted to discuss it, PM me with your phone number and we can have a phone chat. My plan here in Australia gives me unlimited calls to (among other places) the USA and UK (which will dry up soon, as when I go to Finland I'll lose that)

None the less I strongly support;

• weekly measurements (preferably on the same day, no more than a day early / late) and
• dead steady doses with no more than 1mg variance between days of the week and
• minor changes of dose in response to an INR out of target range

I expect you're keen to get past the 90 days, but just relax and it will happen in good time.

 

[vivekd]

Thanks Pellicle. They'll allow me to self manage by end of september.

 

[Agian]

If you believe the On-X people, they say you can drop your INR to 1.5 after 3 months. I'm not fully convinced this is a good idea.

 

[vivekd]

Neither do I, but with On-X, I don't have to bridge if my INR drops to 1.6 (it went to 1.6 last week)

 

[pellicle]

After the GELIA study results in inclined to say that is the case with all the modern bileaflet pyrocarbon designs.

It's also emerging on the literature too that heparin bridging is not an essential procedure in some cases.

 

[MartinF]

I'm late on this, had trouble logging in. I've been on warfarin 3+ years even though I have a tissue valve. Dose is 3 mg 3x a week and 4.5 mg 4x a week. Target range is 2.0-3.0. It's been out of range only twice. Once a 3.3 after a few beers over a 3-day weekend. Beer/wine affects my INR. Once a 1.9 after my wife started adding some greens to my diet. As long as I'm in range I get tested every 6 weeks.
Weight is around 180 lbs., 59 years old.
Was fairly active a year ago, walking/running 25 miles per week.
The last year only doing maybe 10 miles per week. No change in my INR due to change in exercise.
I think I've figured out what works for me.
Martin