A friend has permanent AF, a pacemaker, and was originally prescribed the highest dose of Rivaroxaban (would that be 20mg?) .
Recently he decided to reduce the dose to 10mg because of nose bleeds, heavy bruising etc. The lower dose has eliminated the side effects, however is he protected from stroke? I am encouraging him to check withhis cardiolgist but I'm not sure he will. He has a fairly small frame and is underweight if anything.
I am on Edoxaban and have no experience of Rivaroxaban, I would be grateful for advice.
Not sure if I should be worried or not.
Written by
108cat
To view profiles and participate in discussions please or .
Although there is that general advice re low weight and over 80 for Apixaban there does not seem to be a similar one for Rivaroxaban, I have tried to find out but there seems to be no 'official' ruling. The general consensus seems to be to stay on the AF recommended dose, a few bruises are rather better than a stroke !
An interesting question. How does a doctor or any other specialist know what the best dosage is. When I was on Warfarin the simple INR test could evaluate the coagulation rate. But now I am on Rivaroxaban I do not know how effective it is in reducing coagulation. Why can the INR not be measured? The testing machine does not know what is in the blood, it just measures it.
To the machine blood is blood, is blood, is blood. So it can still measure the coagulation rate, which can then be used as an indicator as to what the suitable dosage should be regardless of the person's age or size.
Warfarin is a vit K antagonist. The DOACs work on a competely diferent part of the clotting process which is does not affect INR so there is no test. They work so they work. Dose was obviously worked out during manufacture.
However, I am still unsure about how effective, or not, the DOAC is for any particular individual.
I understand a DOAC works differently to act on the clotting process within the body.
But how do we know how effective it is.
If it causes the blood to coagulate at a different rate to the norm why can that rate not be measured on an instrument.
(A good analogy is when putting petrol in a car, whether it is 95 octane or 99 octane, the speedometer does not know which, but it can still measure the speed).
The INR (speed of coagulation in seconds) objective for me and many others is 2.5 This arbitrary figure was probably worked out by medical experts, whom we rely on.
But having got AF, which caused my stroke, it would be nice to know how well the DOAC is doing its job.
When medication is given for high blood pressure, its impact can be assessed by measuring BP on a machine.
When medication is given for high cholesterol its impact can be measured by a blood test.
But when a DOAC is prescribed its impact is not measured.
How does a GP know whether to prescribe 15mg or 20mg, to any particular patient?
Apologies for going on about this, perhaps I am missing something!
Many people including doctors and yourself, have explained how a DOAC works within the body. Understood.
But no one can tell me how you can measure its effectiveness.
Why can't the instrument, or some similar instrument, for measuring coagulation rate, be used?
Warfarin works on vit K through the liver and the effect is measured by the international normalisation ratio (INR) with a general level of 2.5 being suitable for stroke prevention in AF . For other conditions it can be up to 3.5 but it is accepted that up to 5 is not dangerous) The DOACs work in a completely different way on a different part of the clotting process to slow down the clotting and there is no test for this. Yes there are tests to check how much of the drug may be present but this does not reflect your stroke prevention. The doses given are the result of experimentation showing stroke prevention . The reduced dose of some DOACs relates only to people over a certain age and or under a specific weight.
To go to your car analogy , you put oil in your engine and it runs for many miles without problem. You may even have put in the wrong grade of oil or used a synthetic one when the enghine was designed for mineral oils, but it will continue to run so long as the lubrication continues. Can you measure how well it is lubricating? In testing engines we anylise oil samples to check for wear particles or contaminates and this can decide what oil is best for that engine just so that the customer doesn't have to do this. Somebody already tested the DOACs before they were approved.
There you go Bob. In testing engines we analyse oil samples to check for wear particles or contaminates. So why do we not test the blood to see what mg of DOAC is best for the individual, so that the customer doesn't have to ask the question. If somebody already tested the DOACs before they were approved, what were the results? It would be useful if there was a sliding scale of recommended mg v BMI ?
It's not a simple question. Yes, he should speak to his cardiologist who will weigh all of the different risk factors and together they can come to a shared decision.
Thank you Jim. Hopefully there's a different one that could protect him without the side effects. Your answer is helpful - my friend thinks it's simple, I'm pretty sure it's not. I just have PAF - my friend has permanent asymptomatic AF. He was here this morning, and had a go on my Kardia - it's quite a fast rate ...
Has your friend seen an electrophysiologist or is he just seeing a general cardiologist? An electrophysiologist would be better equipped to help guide him, given everything that you've said. And I don't know what you mean by "high", but anything over 110 when resting can potentially leave to heart failure over time. And if he exercises, it has to be reasonably controlled as well.
Marginal and probably OK. Maybe a small tweak in his meds? But let's leave it to the electrophysiologists at Birmingham who should be more than capable to both sort this out as well as his Rivaroxaban situation, as long as he listens to them
I agree with Jim. Your friend should discuss this with his medic. The typical full therapeutic dose for stroke prevention in AF is 20 mg once daily (in those with normal kidney function). In some cases, 15 mg once daily might be used if the patient has moderately reduced kidney function.
Reducing the dose to 10 mg daily, as your friend has done, is not a standard dose for stroke prevention in afib. I suggest your friend consults with his/her medic to clarify this matter.
Thanks very much Paul, I agree with you both but wanted to check if 10mg would give him reasonable protection. Clearly not. He obviously needs to contact his medical team.
Being drug averse I tried reducing my heart meds, very gradually weaning myself off one, I'd lost 5 stone so felt my body could cope better, how wrong was I...........went into permanent A/F and heart failure, received a telling off and re-medicated with even higher amounts and now do as I am told because I realise I don't always know best........and that is hard to take!!! Message here, don't mess with your drugs, seek medical advice at all times because we don't always know what's best do we!
There is no guarantee that any of the anticoagulants will prevent a stroke, just make one less likely, plus they can cause a fatal bleed, so if your friend is under weight and bruising a lower dose might be wise. Most doctor's go by their book.
Has he been given a 10mg dose by a doctor or is he just cuting the tablet in half!!! I am on rivaroxaban 20mg, it is a tiny tablet (very tiny) I would think almost imposible to cut in half even with pill cutter. It is said that unless a tablet has the markings to cut dosage on it that you should not do so because it you will not get a proper dose.
An interesting question. How does a doctor or any other specialist know what the best dosage is. When I was on Warfarin the simple INR test could evaluate the coagulation rate. But now I am on Rivaroxaban I do not know how effective it is in reducing coagulation. Why can the INR not be measured by the practice nurse? The testing machine does not know what is in the blood, it just measures it.
To the machine blood is blood, is blood, is blood. So it can still measure the coagulation rate, which can then be used as an indicator as to what the suitable dosage should be regardless of the person's age or size.
Rather than nag my friend on the phone again I've sent an email with all the relevant info you have provided plus the research link posted by OzzieBob that is 100% pertinent.
My dear friend is cutting his 20mg pills in half. A complete no no ...
I’ve only just come across this thread, so I’m too late to add anything useful (I’d just have agreed with everyone else anyway). But I wanted to say that your friend is lucky to have such a good friend in you. We all need people who look out for us, even when we don’t know we need it. (Or especially when we don’t know we need it!)
Hope he responds well to your concern and your email, and that he seeks & gets great advice from his medics. Jx
However, if his renal function is good then rivaroxabab should not be reduced. You mention that they are small- Edoxaban dose is also based on wright, and if little then could perhaps have a lower dose of Edoxaban which may reduce the effects of the rivaroxaban. He needs a conversation with someone who knows his renal function and weight. It’s hard to make a definitive comment on here.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
Rivaroxaban or Epaxiban?
rivaroxaban stomach pain and cramp
Rivaroxaban / endoscopy 
