Does what generic pharmaceutical company used make a difference?

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ncw3642

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Jun 10, 2024
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22
Location
Missouri, United States
Hi all,

New to Warfarin therapy and might have a stupid but curious question here :)

I have both 2mg and 4mg tablets now, both are generic (one is manufactured by Teva and one is Amneal Pharmaceuticals).

Does anyone know if there is a difference in potency/efficacy between brands? From my own past research I know thyroid medication does matter which brand you use. Is Warfarin similar or are all brands created roughly equal?
 
The dosage on the pill seems (to me) to be pretty much the same, manufacturer to manufacturer -- HOWEVER -- when you change manufacturers, it doesn't hurt to test a few days after making the switch just to make sure everything's okay.
Thank you for that!

It seems like my pharmacy doesn’t use ‘one’ generic brand and it seems to be different depending on when I fill a script.

Seems to be good advice all around to just quality check and get more data as I can.

I don’t have access to a home meter yet- (just 2-weeks out) but they do test me 2x a week currently.
 
I have noticed INR changes with different brands over the years. If your drugs are FDA approved, they should all be OK but my experience is to stay with one manufacturer and adjust your INR to that manufacturer's formula.

FWIW, I'd buy only the 4mg tabs and split a tab to get a 2mg......saves a few $$ and most warfarin tabs are "scored" to allow safe splitting.
 
New to Warfarin therapy and might have a stupid but curious question here :)
not stupid

such things are not allowed in Australia because the evidence has shown (to the national body) that INR variations result.

I've seen it here too IIRC ...
I have both 2mg and 4mg tablets now, both are generic (one is manufactured by Teva and one is Amneal Pharmaceuticals).
as long as you keep using Teva for the 2's and Amneal Pharma for the 4's you should be fine. However what may be uncertain is: does two 4's give you the same potency and a shift from 6mg to 8mg as a 2 and a 4 (to make 6mg) vs a 4 and half a 4?. If you were attempting to elevate dose to lean into a change in INR sensitivity this may complicate matters.

Ultimately its uncertain; this study focused on Australian approved brands (which does not include generics)

https://research.monash.edu/en/publ...nticoagulant-brands-safe-coumadin-and-marevan

Abstract​

Aim: Warfarin is the most frequently prescribed antithrombotic agent, available in Australia as brands Coumadin and Marevan. Although both are manufactured by Aspen Pharmaceuticals, there are differences in formulation. The product information states they cannot be used interchangeably. Two incident reports of warfarin brand interchange in our hospital prompted a literature review. We aimed to review published evidence on the pharmacokinetics and bioequivalence of different warfarin brands and make brand switching recommendations.​
Methods: Systematic review of the literature on warfarin bioequivalence and incidents reported by the Therapeutic Goods Administration (TGA). Results and discussion: Fifteen studies explored different warfarin formulations. No significant differences were found in efficacy with brand switching in eight studies analysing participants who were healthy, had atrial fibrillation (AF), or a mechanical heart valve. Prospective observational studies demonstrated no significant difference in the International Normalised Ratio (INR) or adverse events, however, a retrospective observational study demonstrated an increase in complications. Of the four population studies, only one demonstrated elevated rates of haemorrhage or thrombosis. No studies directly compared Coumadin and Marevan. Three TGA case reports describe adverse events from brand switching.​
Conclusion: Studies of different warfarin formulations demonstrate bioequivalence in population studies, but with marked inter-individual variation, hence the recommendation is to continue the same brand of warfarin where possible. However, brand switching is preferable to withholding a dose of warfarin for inpatients, in the absence of the patient’s usual brand. If substituting or brand switching, close monitoring with frequent INR testing is suggested.​

Ultimately "testing" and observation of values will suggest if this isn't the case for unexplained variances.


HTH
 
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The rule I've heard is that once you have your dosages set on one "brand" it is best to NOT switch to another if possible because it is possible doing so can affect your INR in unknown ways. The key is to test test test if switching so to make sure you adjust accordingly with the new brand if necessary.

Of course, with our cost-first-and-patient-second-oriented-healthcare in my experience it happens that your pharmacy may force a different "brand" on you with no warning (this actually happened to me once when they switched generics as a matter of corporate deals/profits/etc).

Ironically just today I switched pharmacies because of some horrible changes with how my current pharmacy (CVS) operates which I can no longer tolerate. I had only about 3 other insurance "preferred" pharmacies in my area to choose from and I was prepared to accept that whichever one I went with would use a different generic supply but I lucked out and one of those uses the same generic as I have been taking the past 6-7 years or so (Teva). I use 3 different pills btw rather than cut any in half (1mg, 2mg, and 5mg).

In your case since you are STARTING your warfarin therapy now I don't think it matters (?). Test with what you'll be taking and adjust accordingly. Probably might be easier to manage or be more predictable if all dosages were from the same manufacturer though (?), at least in theory (?).
 
The rule I've heard is that once you have your dosages set on one "brand" it is best to NOT switch to another if possible because it is possible doing so can affect your INR in unknown ways. The key is to test test test if switching so to make sure you adjust accordingly with the new brand if necessary.

Of course, with our cost-first-and-patient-second-oriented-healthcare in my experience it happens that your pharmacy may force a different "brand" on you with no warning (this actually happened to me once when they switched generics as a matter of corporate deals/profits/etc).

Ironically just today I switched pharmacies because of some horrible changes with how my current pharmacy (CVS) operates which I can no longer tolerate. I had only about 3 other insurance "preferred" pharmacies in my area to choose from and I was prepared to accept that whichever one I went with would use a different generic supply but I lucked out and one of those uses the same generic as I have been taking the past 6-7 years or so (Teva). I use 3 different pills btw rather than cut any in half (1mg, 2mg, and 5mg).

In your case since you are STARTING your warfarin therapy now I don't think it matters (?). Test with what you'll be taking and adjust accordingly. Probably might be easier to manage or be more predictable if all dosages were from the same manufacturer though (?), at least in theory (?).
Thank you for your response.

Since I’ve never needed any prescriptions prior to this procedure the whole process is new to me! In your experience, if I stick to the same pharmacy (mine is actually a part of the hospital I work at since I get a discount for using them), do they typically keep the same generic brands on hand year to year?

I am just surprised they gave me Teva for the 2mg and then a different brand for 4mg. Can I call them beforehand to maybe request or see if the brand is the same when I am getting a refill?
 
In the US drug companies must show generic brands provide an equivalent treatment. Given the number of people on warfarin, if it made a significant difference you'd have been told.

For most drug products, the allowable variation between dose is 90-110% of label claim. Due to the powerful nature of warfarin, in the US, warfarin's variation is held to 95-105%.
 
my current pharmacy (CVS) operates which I can no longer tolerate. I had only about 3 other insurance "preferred" pharmacies in my area to choose from and I was prepared to accept that whichever one I went with would use a different generic supply but I lucked out and one of those uses the same generic as I have been taking the past 6-7 years or so (Teva). I use 3 different pills btw rather than cut any in half (1mg, 2mg, and 5mg).
FYI, I use CVS pharmacy in eastern Iowa USA. My 1mg Warfarin pills are also manufactured by Teva. I have again learned something useful from this forum!
 
When I first had my surgery back in 1998, my Cardiologist wrote the prescription for Coumadin and checked the box that said No Substitutions. He said that there wasn't enough oversight of the generics and since Coumadin is so specific and a tiny bit can make a huge difference, it was best to stick with brand name. The generics had only been approved in the US for about a year at that time and many doctors were leery. At some point maybe 5 years later he started prescribing Warfarin and I asked him about it. He said he had followed the testing and was more confident in the generics. He did recommend that I let the pharmacy know that I didn't want generics from India because he felt there were issues in some of those. However, that was about 20 years ago and I now take whatever I get. I get 90 at a time and when I get a new bottle, i mix the old in with them. I've never noticed a difference and was pretty stable for many years until I recently started taking Nexlivet which lowered my Warfarin need from 7.5 to 5 daily, but that has nothing to do with the manufacturer of Warfarin.
 
In the US drug companies must show generic brands provide an equivalent treatment. Given the number of people on warfarin, if it made a significant difference you'd have been told.

For most drug products, the allowable variation between dose is 90-110% of label claim. Due to the powerful nature of warfarin, in the US, warfarin's variation is held to 95-105%.
I have had no problems with the differences of the manufacturers of Warfarin. For it depends on diet, physical activity and OTS medications that affect my Protime.
 
Thank you for your response.

Since I’ve never needed any prescriptions prior to this procedure the whole process is new to me! In your experience, if I stick to the same pharmacy (mine is actually a part of the hospital I work at since I get a discount for using them), do they typically keep the same generic brands on hand year to year?

I am just surprised they gave me Teva for the 2mg and then a different brand for 4mg. Can I call them beforehand to maybe request or see if the brand is the same when I am getting a refill?
Depends on many factors, including the contract with the manufacturer. Sometimes the pharmacy will change with a different manufacturer after a contract is over. But it is still generic Warfarin and is the same drug, same ingredients, but a different manufacturer.
 

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