Friday 16 June, 2006

How to start warfarin therapy

Posted in General Practice, Medicine, Michael Tam, Wards at 14:58 by Michael Tam

Index: Anticoagulation :: Printer friendly

Original article by: Michael Tam

Warfarin is an interesting medication – it saves many lives but causes many problems including some deaths of its own. At present, it is the only oral anticoagulant available in Australia and it is a commonly used drug. Warfarin management, however, is done notoriously badly in hospital.

The key to warfarin management is patience

The effective half-life ranges from 20 to 60 hours with a mean of about 40 hours (1). It takes around 3 half-lives to approach steady state and 5 half-lives to reach steady state. That is, for most patients it will take about a week before steady state is reached (and even longer for others). I have seen far too often in hospital people changing the dose of warfarin too rapidly with the result of the INR fluctuating up and down.

Step 1: Consent

Bleeding to death is a particularly unpleasant way to go and warfarin isn’t the safest drug if used inappropriately. Documented informed consent is necessary. Even better, arrange for a clinical pharmacist (if in a hospital) to counsel the patient on warfarin.

The annual incidence of fatality due to warfarin is oft quoted at around 1% though it is more likely to be around 0.2%. About 15% of patients have at least one minor bleed a year (2).

Step 2: Anticoagulation with heparin

Warfarin works by being an antagonist to vitamin K. Vitamin K is the cofactor in the production of the (not surprisingly named) vitamin K dependent clotting factors (Factor II, VII, IX and X). However, the anticoagulant enzymes Protein C and S are also dependent on vitamin K and have shorter half-lives than the clotting factors.

Thus, when you first start warfarin, there is a paradoxical initial pro-thrombotic effect. Other forms of anticoagulation are a necessity.

Usually, by the time a clinical decision is made to commence warfarin, the patient is already on unfractionated heparin (UFH) or low molecular weight heparin (LMWH). However, this is not always the case (for example, discovering that the cause of a stroke is paroxysmal atrial fibrillation) so always remembering to anticoagulate with UFH or LMWH first is important.

Step 3: Start warfarin

If a patient has previously taken warfarin and had been stable on a particular dose, then start with that dose. Otherwise, check their baseline INR and start:

warfarin 5 mg daily (nocte) for three doses

Step 4: Check INR on the morning of day 4 and adjust the dose

INR (morning of day 4) Change warfarin dose to
< 1.3 increase to 7 mg daily
1.3 – 1.7 continue with 5 mg daily
1.8 – 2.5 decrease to 3 mg daily
> 2.5 decrease to 1 mg daily

Note: This is my personal opinion only – I do not believe in giving “loading doses” of warfarin. I believe that the dose of warfarin you should be giving is what you consider to be their “maintenance” dose in the longer term. There are other “initiation schemes” (here and here) that are designed for rapid attainment of the therapeutic level so the patient can be discharged earlier and come off other forms of anticoagulation.

Unfortunately, what commonly happens then is that the patient is discharged on much too high a dose with a high INR in 1-2 weeks time; much to the annoyance of the general practitioner, potentially risking a serious bleed in the patient, and will come back to bite you in the buttocks if they get readmitted.

Step 5: Stop heparin when INR reaches therapeutic levels

Some institutions would advocate daily INR tests until it reaches a therapeutic level (INR between 2.0 and 3.0). When the INR is 2.0 or above, the UFH or LMWH can be ceased and the patient discharged (if medically appropriate).

Some areas have an outpatient team that can warfarinise a patient at home. They have daily blood tests and a doctor calls them for their next dose of warfarin. A community nurse usually helps administer a LMWH like enoxaparin (Clexane) subcutaneously at home.

Step 6: Regular INR checks

Once the warfarin level is therapeutic, INR need only be performed every 1-2 weeks initially for a new patient. Changes in the dosage of warfarin should be to what is estimated as the maintenance dose. The practice of deliberate under or overdosing to more “quickly” reach the desired level should be avoided.

Remember that most GPs would only do the INR fortnightly.

For a stable patient, the INR needs only be performed perhaps once a month.

Step 7: Continuing warfarin education

It is important to educate and remind patients about warfarin – usually done by the general practitioner but it should be addressed for patients who are on warfarin and admitted to hospital. Medication compliance, education on diet (e.g., eating consistent amounts of vitamin K rich foods), drug interactions, avoiding unnecessary over-the-counter “vitamin” pills are all significant issues in the longer term management of a patient on warfarin.

Hints and tips

  • Be aware that there are two brands of warfarin in the Australian market, Coumadin and Marevan. Unfortunately, they are not bioequivalent. The public NSW Health system only uses Coumadin. Though perhaps not particularly fair on the company that makes Marevan, I advocate using only Coumadin as it causes less confusion when the patient is admitted to hospital.
  • Many patients can’t remember their dose, but remember the colour tablets that they are on. For Coumadin:
    • 1 mg tablet = light tan
    • 2 mg tablet = lavender
    • 5 mg tablet = green
  • If the patient is on a “3 mg tablet” of warfarin, then they are on Marevan:
    • 1 mg tablet = brown
    • 3 mg tablet = blue
    • 5 mg tablet = pink
  • Half milligram doses are difficult for the elderly as they may not have the manual dexterity to break or cut a tablet in half. Consider alternate day full milligram doses instead (e.g., rather than 4.5 milligrams daily, 4 milligrams and 5 milligrams alternate days).
  • A pill box or blister pack and help many people stay compliant on their warfarin (and other medications as well).
  • It is useful to have a good grasp on when and how to reverse warfarin when there is a high INR result (3).

A useful resource – an estimate of the final maintenance dosage of warfarin after commencing on 4 consecutive days of 5 mg daily dose (4):

INR (morning of day 5) Warfarin dose per week
1.0 71 mg
1.2 48 mg
1.4 39 mg
1.6 33 mg
1.8 29 mg
2.0 26 mg
2.2 23 mg
2.4 21 mg
2.6 19 mg
2.8 17 mg
3.0 16 mg
3.2 14 mg
3.4 13 mg

Reference articles

(1) Coumadin (warfarin sodium), MIMS, 1 April 2006.

(2) David A Fitzmaurice, Andrew D Blann, Gregory Y H Lip. Bleeding risks of antithrombotic therapy (ABC of antithrombotic therapy). BMJ 2002;325:828-831 (12 October) [download PDF :: 258 Kb]

(3) Tam M. How to reverse warfarin [electronic article]. The Medicine Box. Last updated 23 June 2006. [Link]

(4) Pengo V, Biasiolo A, Pegoraro C. A simple scheme to initiate oral anticoagulant treatment in outpatients with nonrheumatic atrial fibrillation. Am J Cardiol 2001;88:1215.

Updated: Michael Tam (20 July 2006)

Please read the disclaimer


  1. Michael Juniper said,

    Hi, I have a couple of questions that I can’t seem to get proper answers to from the doctors. My wife was diagnosed with a large clot in her groin in January. She was given what appears to be the standard dose of Warfarin to get her INR to between 2 and 2.5 by DVT nurses. The usual practice is not to see a consultant until 16 weeks after diagnosis although after pushing we managed to get an appointment sooner. Her dosage it appears should have been much higher in order to try and disperse the clot. Now after 6 months the clot is still there. What are the chances of it dispersing now? What are the chances of getting another one after coming off of Warfarin? Do the risks of staying on Warfarin for life outweigh those of another clot? Thanks

  2. Michael Tam said,

    Firstly: read the disclaimer.

    Remember that I am not your regular physician. I do not have all the clinically relevant information. The below is simply my opinion on the limited information that you have provided me.

    After a DVT (deep vein thrombosis), the standard therapy is anticoagulation with warfarin to achieve an INR target between 2 and 3 (so a target of 2 to 2.5 is entirely appropriate). A higher dose of warfarin would not significantly reduce the risk of a venous thromboembolism or extension of the thrombosis while increasing the risk of bleeding complications.

    Warfarin is not a thrombolytic (clot dissolving) agent. That means, it does not break down or “disperse” clots. The purpose of anticoagulation with warfarin is to prevent the extension of the thrombosis and to prevent thromboembolism (i.e., clots breaking off and lodging in the lungs causing pulmonary embolism and pulmonary infarction). It does this well and with warfarin therapy, the risk of a pulmonary embolism is reduced 5-10 fold compared to no treatment.

    I do not have enough information from you with regards to “the clot is still there” to know actually what that means. Unfortunately, anticoagulation with warfarin alone often does not lead to complete recanalisation (i.e., reformation of the “bore” of the vein) and even if it does, the venous valves are often destroyed. This increases the risk of longer term problems in some people such as chronic venous insufficiency of the limb.

    For your information, it is the body’s own natural clot dissolving enzymes that break down the thrombus and recanalise the vein.

    Assuming that it is safe to discontinue warfarin at this point (a decision that will be made by your specialist) there is an increased risk of DVTs in the future. The risk is about 5 times increased risk compared to baseline.

    Unless there are some specific risk factors (including recurrent DVTs or pulmonary emboli, malignancy, inherited clotting disorders), it would not be standard practice to go onto life long warfarin after the first DVT.

    There is some evidence that early thrombolytic (clot busting) therapy or even thrombectomy (i.e., surgery to remove the clot) may lead to better long term outcomes insofar as better vein patency and lower risk of chronic venous insufficiency. These therapies, however, are not without considerable risk and it is controversial as to whether the risks of these invasive therapies are worth the gain.  In any case, they are not “routine” treatment for lower limb DVT (in Australia at least, though I’m fairly sure the situation is similar in the United Kingdom).

    Reference article

    (1) Feied C. Deep Venous Thrombosis [electronic article]. Emedicine. Last updated 20 March 2005.

  3. Aleta Lannert said,

    I have been on warfarin since may after a gall bladder surgery and it is doing strange things to me and I dont like it. I want to go off of it but dr says procedure is six months which will be in nov. but I am thinking about going off of it now. When they did a ct scan in may they said it was already disappating and healing itself so could it be gone by now or will it ever go away. I want my dr to do another ct scan but she said they dont do that because it will always show something like where it was scarring or something that will always be there to show up. I have muscle aches horrible and keep getting sick with respitory infections and think my immune system is low because of warfarin. Anything you could tell me would help. Sincerely Aleta Lannert

  4. Michael Tam said,

    Firstly: read the disclaimer.

    Remember that I am not your regular physician. I do not have all the clinically relevant information. The below is simply my opinion on the limited information that you have provided me.

    I have had to extrapolate from some of the details in your comment. I assume that you are on warfarin for a pulmonary embolism (clot in the lung) after your abdominal surgery (diagnosed on a CT scan).

    First, in terms of the side-effects from warfarin, it can uncommonly cause fatigue and lethargy (1) and perhaps some myalgias. It does not, however, lead to more frequent infections. Warfarin has no effect on the immune system. If I had to guess, I do not believe that the bulk of your symptoms are as a result of the warfarin. The recurrent respiratory tract infections could be the cause of your myalgias in itself.

    Nevertheless, if you are keen on cessation of your warfarin, it is best done in consultation with your regular physician. Alternatives include replacing the warfarin with enoxaparin sodium (a once a day subcutaneous injection) or simply stopping anti-coagulation altogether.

    With regards to your risk, the recommended length of treatment with warfarin is 6 months (assuming you have had a pulmonary embolus). If the PE was triggered by immobility during surgery, then your baseline risk should return to near normal, though it will probably always be somewhat higher than compared to someone who has never had a deep vein thrombosis of venous thromboembolic disease. Stopping warfarin at this stage does increase your risk of recurrent disease though the absolute difference would probably be small compared to cessation of warfarin at 6 months. If you have some underlying thrombotic tendency (e.g., cancer or family history or known thrombophilic condition), then continuing for the full course of warfarin would be highly recommended.

    If the CT scans are to look at resolution of a pulmonary embolism, then a follow up scan would not be required (or recommended). Remember that you receive a significant dose of x-ray radiation with each CT scan (close to 1-2 years of background radiation at sea-level).


    Coumadin (Warfarin sodium). MIMS Online. Last updated: 11 July 2006


  6. Michael Tam said,

    Firstly: read the disclaimer.

    Remember that I am not your mother’s regular physician. I do not have all the clinically relevant information. The below is simply my opinion on the limited information that you have provided me.

    If your mother has a condition that causes chronic pain, then it would seem reasonable that she receives therapy that adequately treats that pain to her satisfaction. That may not be with pharmacotherapy or pharmacotherapy alone. Nor does it necessarily mean that the acceptable endpoint to be a complete absence of pain, especially if that results in side-effects or that it would compromise other therapy.

    The fact that someone is at the age of 84 years is not a contraindication to warfarin. It depends on a number of factors including: (i) the risk of the underlying condition being treated by warfarin, (ii) risk of warfarin itself, and (iii) quality of life issues surrounding warfarin therapy (e.g., the need of regular blood tests).

    Whether your mother would be “better off” on or off warfarin would depend on why she is on it in the first place as well as her general state of health. For example, is she frail and prone to falls?

    I do not have the adequate information in your comment to be able to quantify the risk balance and make a judgement, but a common example is the use of warfarin in the prevention of strokes (e.g., in someone with atrial fibrillation or who have had multiple strokes on aspirin previously). In this situation, warfarin therapy is usually indicated from a survival perspective unless the patient is particularly frail or unstable as it drastically reduces the risk of death or a debilitating stroke.

    Quality of life issues, of course, are difficult to quantify and are very individual. A patient may be willing to accept the increased risk of death or severe stroke to save from being on warfarin. These complex management decisions are best made by your mother in conjunction with her regular general practitioner.

    With regards to analgesia with warfarin, non-steroidal anti-inflammatories (NSAIDs) are generally contraindicated as there is an increased risk of bleeding complications. They can still be considered, nevertheless. Furthermore, opioid analgesics can be used with warfarin quite safely. Non-pharmacological measures for chronic pain should always be remembered (e.g., physiotherapy, local physical therapy, massage, etc.).

    In essence, I do not believe that warfarin therapy should preclude the adequate control of pain.

  7. Fiona Howarth said,

    I had a DVT last March which then dispersed and produced PEs in both my lungs (multiple ones – large rhomboid in my right lung). This led to pain when breathing and I suffered from total exhaustion.

    I was prescribed Warfarin and have been taking this since March last year – I was on the Pill for 3 months before the DVT (I hadn’t been flying), I had smoked a little, was 42 at the time and was 2 stone overweight.

    Exercise was one of my tools to keep my weight down but as I also have a worsening disc problem in my lower spine, it has been very difficult to get back into exercising although I do swim and do regular 20 mile bike rides.

    I have two issues now:
    a) I would like to lose weight quickly as I can;t stick to slow weight loss diets – I have been prescribed Xenical to help lose weight to sort my obesity and disc problem out – been to see about a very low cal diet today (500 cals) and am told I cannot do it as I am on warfarin and need to be off it for min 6 months before I can go on it. I can’t wait for 6 months!
    b) I have asked to come off Warfarin – haematologist says it was caused by the Pill and I could come off, although my GP thinks there are other factors in my family history (my Grandmother had massive stroke at 30 and her sister had one at 40) so has advised me to stay on Warfarin for life. My INR is still not under control (last Friday was down to 1.2 again as I missed a couple of doses).

    Without doing something drastic to lose weight, I feel I am just getting fatter and fatter, my back is causing me to become depressed as I have had chronic pain for 3 years now which is impairing my ability to walk.

    I have tried dieting, using the Xenical and doing lots of exercise (60 x 25 m lengths per day, 25 mile bike rides!!) but with no apparent results. I just can;t seem to even lose 1lb after 3 weeks of dieting.

    Can you suggest somewhere positive for me to start to get out of this downward spiral PLEASE???


  8. Michael Tam said,

    Firstly: read the disclaimer.

    Remember that I am not your regular physician. I do not have all the clinically relevant information. The below is simply my opinion on the limited information that you have provided me.

    There are firstly several issues here that I will discuss one at a time.

    If it is true that you have two family members with strokes while they were young (i.e., in their 30s and 40s), then it is possible that you have an inherited tendency to have blood clots. Does your haematologist have this history? Have you been tested for the common ones? Without more information, I cannot make an opinion one way or another whether you should remain on warfarin.

    Smoking and being on the combined oral contraceptive pill (in your 40s) is definitely a risk factor for clots. If they were your only risk factors, then yes, lifelong warfarin would not be indicated after cessation of the pill and smoking.

    Insofar as using tablets to help with weight loss, they are generally unhelpful. Orlistat (Xenical) only results in a mean loss of around 3-5 kg of weight and most people regain that weight on cessation of the medication. I would also recommend against using orlistat with warfarin. Orlistat works by reducing the absorption of oral fat, and vitamin K is a fat soluble vitamin. Fluctuating levels of absorbed vitamin K would likely make it difficult to maintain a stable INR when taking warfarin.

    Low calorie diets are also generally unhelpful. You may lose weight quickly initially, but it results in a substantial lowering of your basal metabolic rate as your body adjusts to the “famine”. When that occurs, you will feel tired and lethargic and the weight loss stops as your body tries to maintain its energy stores. In addition, much of the weight lost (initially) is in body water and muscle rather than fat.

    Loss of weight is less important than achieving good cardiovascular health. At the end of the day, it is a simple energy equation. If you eat more calories than you expend, you will put on weight. Where it is balanced, your weight will stay the same. Where you use more energy than you eat, then you will lose weight.

    My suggestions include the following:
    (1) Stop dieting. They almost never work for the above mentioned reasons. What you should be aiming for is a balanced diet with sufficient nutrition for long term health. I would recommend seeing a nutritionist or dietician for education on what a balanced diet actually is as well as portion sizes. Most people simply eat the wrong foods and have too much of it.

    (2) Avoid medications for weight loss. Again, they almost never work in the long run. There is no magic bullet (at the moment) and without effort to change lifestyle, weight loss will not be sustained. Tablets result in a disincentive to change lifestyle so work against you in the long term.

    (3) Continue with your exercise routine. Exercise is the backbone to weight loss but it will not come quickly. The reality TV shows like “The Biggest Loser” actually do give you an idea of how difficult it is. Exercise, however, will improve your cardiovascular fitness and improve your body profile of fat to muscle.

    (4) Work for your food. Buy dumbells (about 2 kg or 6 lb) and lift them for 5-10 minutes until you are breathless and have sweat before EVERY meal.

    (5) Bike riding for exercise. It is very easily to end up coasting while cycling. For weight loss, your goal should be that you are cycling to the intensity such that you feel your heart pounding and a bit short of breath.

  9. cherry said,

    I have seen a case had a stroke after the dentist stopped his Warfarin. What is the suggestion for the patient who are on wafarin and need a dental procedure?

    Thank you.

  10. Michael Tam said,

    Read my article on How to stop warfarin for surgery.


  11. David said,

    My brother, after a stay in the hopital where it was discovered that he had clots, was placed on Coumadin 10mg. He remained on this dosage for 5 months, as that is when his prescription expired. Up until this time he was feeling fine. When he went to refill, the pharmacy had to call to get a new prescription, this time for 5mg. Shortly after this, a clot went to his lung and he had to be hospialized and had a net placed into his leg. He is back home now and the attending wants to increase his Coumadin because his blood is too thick.

    My question is simply, could the change from 10mg to 5 mg so suddenly have caused his clotting to worsen? Is this something that he should watch for in the furture and call his attending when the dosage changes?

    Thank you,


  12. Michael Tam said,

    Firstly: read the disclaimer

    Remember that I am not your regular physician. I do not have all the clinically relevant information. The below is simply my opinion on the limited information that you have provided me.

    There is not a lot of information that you have provided but treatment with warfarin (Coumadin) needs to be regularly monitored. This is initially with daily blood tests until the INR (international normalised ratio) value is within the therapeutic range (usually an INR between 2 and 3).

    The INR is a measure of the degree of anticoagulation (blood thinning) that has occurred.

    Once the INR level and warfain dose has stabilised, blood tests to monitor the INR would commonly be performed every 2-4 weeks, ad infinitum.

    In the situation where the regular dose of warfarin was 10 mg and it was dropped to 5 mg without monitoring, then it would be reasonable to assume that the anticoagulant effect would be inadequate.

    I am uncertain of the exact scenario that has occurred with your brother but he should have a regular doctor who is looking after his warfarin dose. He should be having regular blood tests to monitor the INR. He should not be having any changes in the dose of his warfarin that is not advised by his regular physician.

    Best regards.

  13. john nemeth said,

    I am on warfarin because I have been diagnosed with Atrial Fibrillation last February. The medication I take for it seems to be working (flecainide) in that I have only had a few relapses lasting for a few days before I’m rhythmic again. I have no symptoms of anything and am in good health as I jog frequently. Now after any meal I am so tired I have a hard time staying awake and at night I am up and out of bed frequently. I think warfarin is slowing down my metabolic rate way too much. Any ideas?

  14. Michael Tam said,

    Fatigue is an uncommon but known side-effect of warfarin. On the other hand, consider why you are on warfarin; to substantially reduce the risk (~70%) of a thromboembolic stroke.

    If you are having intolerable side-effects, I strongly recommend that you see your regular physician to discuss your long term management plan.

    Best regards.

  15. john nemeth said,

    Thanks, Michael. I appreciate your timely response. Unfortunately I have trouble getting into a deep sleep as I typically wake up every two hours. This sleep issue may be more of a problem itself than a consequence of the warfarin.

  16. De Silva said,

    Dr. Tan,

    When a patient is diagnosed as having DVT and the decision has been made to thrombolyse, when is the best time to start the Warfarin?
    Is it started on day 1 along with Heparin or a few days later?

    De Silva

  17. Michael Tam said,

    Dear De Silva,

    If by “thrombolyse” you actually mean “anticoagulate” (i.e., using heparin/warfarin rather than streptokinase), the best time to start warfarin is along with heparin. However, one must ensure that the patient is already anticoagulated first with the heparin (i.e., there hasn’t been a delay with starting the infusion) before the first dose of warfarin.

    Warfarin affects the vitamin K dependent clotting factors (factor II, VII, IX, X) but also protein C and protein S. As protein C and S have the shortest half-lives, they tend to be affected first. Both are involved in the thrombolytic pathway. Warfarin on initiation has a slight prothrombotic effect so cover with another anticoagulant is a must.

    Best regards.

  18. Jacqui Jackson said,

    My mother has been on warfarin for the last four years. Since first being prescribed this drug a previously mentally alert person has become confused and forgetful. It is noticable that when the dosage is at it’s lowest my mothers levels of confusion decrease also. I have not seen any reports of this being a major side effect can you give a possible explanation please.

  19. Michael Tam said,

    If you are asking the question whether the warfarin is responsible for the cognitive decline, the answer is that it is highly unlikely. Without any further information, it is impossible to know the cause but if I had to guess, progressive and persistently confusion and forgetfulness is consistent with a dementia.

    Warfarin does infrequently cause lethargy and malaise in some people and it is possible that you may be noticing some dose related effect.

  20. natalie said,

    hi im 27 and i had a pulmonary embolism as a result of an elective section,i had a blood tranfusion and i wasnt mobile after the section.i am on warfin and i am due to come off it in may,im so nervious as i find warfin a brilliant drug and it has helped me,my question would be is it possible to get another embolism if i just stop the warfin,my gp told me 12 months on it is long enough and i can just stop it,but i notice if i forget to take it my skin becomes itchy and when i scratch myself big red marks appear on my skin and other people notice this and say to me did i forget to take my warfin,as soon as i take it my skin does be any advice for me about comming of it.

  21. Michael Tam said,

    Dear Natalie,

    If you have trouble with your skin, then you should seek the advice of your regular General Practitioner. Most people have no difficulty stopping warfarin.

  22. David said,

    Thanks for the handy summary.

    Don’t feel sorry for the company that makes Marevan. Coumadin and Marevan are now made by the same pharmaceutical company: Marevan by Fawns and McAllen Pty Ltd, which is a member of the Sigma group of companies; and Coumadin by Sigma Pharmeceuticals Pty Ltd.

  23. Hayden said,

    I’ve just been diagnosed with a dvt in the lower extremity of my left leg. The doctors say it’s not to bad that my body should absorb the clot but, they wanted to take a pre-caution and put me on 0.7 lovenox (for 5days) and 7.5 of warfarin. I’ve been taking it for the last three days and my body is feels like somebody is rolling a truck over it. I guess you can say it’s muscle cramps but my question is could this be too much. My PCP say’s she will decrease the dose to 5mg of warfarin but I have to wait at least a week to finish the 7.5 Again, does this seem like a lot for something they said my body should absorb because of the clot location.

  24. Michael Tam said,

    Dear Hayden,

    The appropriate dose of warfarin for an individual ultimately depends on the target INR range. If you need a higher dose of warfarin to reach the target INR, then you need a higher dose. Conversely, if you need a lower dose to reach the target, then you need a lower dose.

  25. john currier said,

    My wife has a dvt. She has started cumodin therapy and was taking lovenox injections and progressing very well in mobility. One and a half weeks after stopping the injections at doctor’s orders, she rather suddenly has had the pain return and is running a low grade fever. Swelling, discoloration, and tenderness of her leg has returned. We are understandably very concerned though the doctor’s only instructions are to resume lovenox injections. Is this recurrence common and how serious is it?

  26. Michael Tam said,

    Firstly: read the disclaimer

    There is only scant clinical information that has been given but the story as you have relayed it seems consistent with a extension of the DVT. The issues here is whether anticoagulation has been adequate on the oral warfarin.

    This should be taken seriously.

  27. Bobby Rattan said,

    Hi, I am a Warfarin patient and lately my INR has been very eratic, from 1.04 to 3.
    Recently i ahve been advised to watch my diet, as i am a strict vegetarian, can you recommend a few variations.
    Morning 1 scice of Rye Bread with a slice if cheese, a handfull of all bran with Skim Milk.
    Lunch: 5 different types of fresh fruit.
    Dinner; a mild veg curry with Basmati rice, Steamed Brocoli,Cauliflour, Sweet Potatoes and a bit of Green Salad.

    My daily medication is;
    Cordarone 200mg
    Prexum 1 tab
    Isoptin SR 240 mg
    Warfarin 5mg , changes in dosage depending on INR
    Cholastrol teb

    Will appreciate any assistance

    Kind Regards

  28. Michael Tam said,

    Dear Bobby,

    I am not a dietician so I can only give you generic advise. Basically, being a vegetarian is not a contraindication to being on warfarin. However, it would be worthwhile investigating which foods are rich in vitamin K (e.g., green leafy vegetables) and then trying to have a consistent quantity of vitamin K rich foods on a day by day basis.

    It is not so much a matter of avoiding certain foods but aiming for consistency.

  29. Danielle said,

    Hi there
    I am due to come off warfarin (5mg dose) in 3 days and my partner and I want to start trying for a baby. What is the general recommendation regarding the amount of time you should wait after stopping warfarin before concieving?

  30. Michael Tam said,

    The use of warfarin in the first trimester is not recommended due to the increased risk of foetal abnormalities. I do not believe that there is any general recommendation about the amount of time before conceiving. Warfarin will be out of the system within 5-7 days of cessation.

    Please see the following for an expert opinion on anticoagulation in pregnancy published by the American College of Cardiology.

  31. Betty Matthews said,

    I am a long-time user of warfarin and coumadin for a-fib. I have been unable for the last year to stay at an INR level of 2-3. I run 1.8 or so and we have been adjusting every 2 weeks to try to level it. We have checked every interaction with my meds, with my diet, etc. My question is the usage of well water. Have you heard of that causing a problem. Also, I do not hydrate myself well. Would these issues have a bearing on the INR level? Is there any difference in the stability of warfarin and coumadin – some physicians have said yes, some say no.

    • Michael Tam said,

      I have not heard of well water being a problem, however, no one uses well water where I live and work. Furthermore, “Coumadin” is simply a brand name. The active chemical in Coumadin is “warfarin”. In Australia, the two brands of warfarin are not bioequivalent meaning you cannot switch between the two and expect an equivalent effect. I would recommend staying on the same brand of warfarin.

      Otherwise, the best way to try to stabilise the INR is to ensure that dietary intake is similar week to week, especially for vitamin K containing foods.

  32. Lagese said,

    Dear Mr Michael Tam

    My Mum had valve replacement four years ago and she is on warfarin for almost 5 years. the last month almost every week she had a very high INR and today itself her INR level is 5.9. We went for several test today to check if everything is fine but do not understand why the INR keeps remaining High. she takes a general dose of 6mg to 5mg and this was going on fine but now Doctors keep on changing the dose without any result. Could it be that there is something else apart the warfarin causing this problem that is any health problem?? If that is so for what further test should we do to know what is happening??

  33. James Anderson said,

    I just wanted to say what a great site this. A very valuable resource for all those in health care. As a pharmacist it is great to see your interest in and grasp of pharmacotherapy.

    I just wanted to mention in reference to John Nemeth’s post it is more likely the flecainide causing any excercise intolerance or fatigue than the warfarin.
    But of course if he is still concerned he should see his primary care physician for a more thorough assessment



  34. aunbis said,

    I am a type 1 diabetic on an insulin pump, have hypothyroidism, factor Five Leiden deficiency, and anemic. I have 5 stents in my left hip area because of a DVT in 2005. I had 15 PEs in my lungs after being taken off of warfarin because the docs thought it was only pregnancy related. They then found out that it was due to factor five Leiden deficiency. I have now been on warfarin since 2006 and was told then that I would never come off of it. My INR fluctuates constantly and my leg is always sore. I want to stop the warfarin therapy. What are some of the effects and how quickly could any of these effects happen?
    Thank you.

  35. wendy said,

    hello, i develped a blood clot in my right arm last november, it was a very large clot, i started warfarin immediatley plus injections,after 6 weeks my inr has stayed between 2.3 and 2.8….i had a ct scan before xmas but it didnt show up anything that could have caused the clot so they have put it down to me being on the combined pill and smoking (i am 38)
    i am due to come off warfarin in may but i am really worried about developing another clot…if it was the the pill that caused it then surely it wont happen again if im no longer on the pill?

  36. harpreet said,

    hi dr.,
    i’m 13 wks pregnant,age 34,G-5 with1 live male
    child.this time i underwent blood tests series like
    protein c&s,b-2-glycoprotein,APAs,lupus,KCT,aPTT
    and dual tests.all went well but protein c was decreased(38).
    i also had been taking aspirin since my 5th wk. now my gynac had put me on lmwh which i’ll have to take for next 5 months.
    i’m worried as i was on aspirin when i went for test.

  37. Don said,

    Hi: My name is Don and about 24 months ago I had a DVT behind my knee. I was prescribed Coumadin/Warfarin. Over the following 18 months ( I have Factor 5) I did not feel well at all. Lethargic, rash, extreme fatigue and all the rest. I finally stopped the Coumadin/Warfarin about 6 months ago. Since then I have had all kinds of blood tests for everything and my Doctor says my remaining fatigue, stomach problems etc. are all related to stress and have nothing to do with the Coumadin/Warfarin. My question is how long till your body gets back to normal after stopping these medications? Please tell me your thoughts as I hear some people bounce righ tback and others it takes months and also some people tell me they feel like these drugs are the same as Chemo. Thanks

  38. my 76 yr old dad had a P.E following surgery in 2010 . he was treated on Warfarin for 6 months then it was discontinued. Six months later he developed a DVT in his right lower leg so he was put on longterm Warfarin use. His INR is good at his maintainence reading of 2.5 – 3. Tonight however hes been to his GP with a swollen painful lower left leg and hes now awaiting a scan to see if he has another clot. Why would this happen when hes on Warfarin? and if its another clot what can be done for him now ?

  39. shxr said,

    Hello, can I know why is there a need to have two different brands of warfarin? (Marevan and Coumadin)
    And the difference between these brands is just about the different strengths?

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