Hello Hope all is well. I have a question for Dr. @availlant, Dr. @ThomasTu Dr. @john.tavis or @Bansah1
Im on TDF since the end of October, I live in-between Italy and USA.
I’m currently in Italy and my Italian epatologist has just switched me from TDF to TAF, because there isn’t any TDF available at the moment in Italy.
when do I go to USA do I have to carry on with TAF ? or can I go back to TDF ( cheaper than TAF in USA)
my question: is it ok to switch back and forth between the two? ( TDF and TAF)
Thanks you for your time.
Gregory
Hi @Gregory,
I will think staying on the TAF for consistency will be the way to go rather having to go back and forth between the two. Switching from one to the other is safe, but I am not sure what will happen if you need to change that many times. I hope this makes sense. Best, Bansah1.
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Thanks you!
It makes sense, I was just wondering since they are both Tenofovir.
They do have some similarities but TAF is much improved version of TDF. I am more concerned whether the frequency in switching could lead to viral resistance or being less effective? I don’t know what the science is on this.
I do know that switching from one to the other is safe (i have done that in my care), but not sure how it works in the situation you describe where you go back and forth between the two.
Thanks, Bansah1
TDF Is known to cause side effect such as osteopenia and chronic kidney disease particularly on underweight individuals. TDF losses its patent so it should be cheaper . TAF is safer. M
Hi all,
I see no biological reason why shifting from TDF to TAF and back to TDF would cause a problem, presuming you are tolerating TDF well. TAF and TDF turn into the same drug (tenofovir) once they are in the liver, and the dosages are calibrated so that the amount of TAF is the same or somewhat higher in the liver than with TDF. So as long as there is no gap in taking the drug when shifting between the drugs, there will be no elevated chances of resistance evolution. Plus, primary resistance to tenofovir (either as TAF or TDF) is extraordinarily rare. You should be good.
The only caveat is that I am not a physician, and sometimes the complexities of how drugs are processed in the body are beyond my expertise. So I’d go with whatever your physician recommends, remembering that a gap in treatment is almost certainly worse than any issues that may arise from shifting drugs.
John.
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Dear @Gregory,
There is no issue with returning to TDF from TAF therapy from an overall safety and efficacy standpoint.
Conversion from either prodrug to the active tenofovir diphosphate (TFV) form in liver cells occurs with similar reaction kinetics. The main difference with TAF is that is has greater accumulation in the liver than TDF due to the alafenamide modification used in place of disoproxil fumarate in TDF. As a result, TAF can be given with a lower daily dose (25mg TAF vs 300mg TDF) and still have the same activity because it achieves the same active levels of TFV in liver cells. You can read more about this here.
The one thing to remember is that, due it the less efficient delivery of TDF to the liver, the high higher dose required of TDF for good efficacy results in increased systemic exposure. In some cases, chronic TDF therapy can lead to mild alterations in kidney function and bone density. It the majority of cases, these changes have little to no clinical impact. However, in a small minorty of patients, switching to dosing of TDF every other day or to daily TAF may be required.
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Hello, I hope all is well.
Can someone please help me understand how it works with insurance coverage and Gilead vouchers for TAF ( vemlidy) in USA?
I live in between USA and Italy, I haven’t asked my insurance yet if it covers TAF I just looked online and it says its Tier 3 (with my Insurance). Is it very expensive? how does it work between insurances and Gilead voucher programs?
Thanks you in advance for your kind response.
Gregory
Hi @Gregory,
Good question. I don’t know how these insurance companies work. Initially my insurance would not cover Vemlidy, but after my doctor submitted further evidence it was approved. But every year, my doctor sends information for a new approval. Yes, Vemlidy is expensive $1300-$15000 for 30 tablets without insurance. I don’t think you can combine insurance with the voucher. I have never used the voucher for Vemlidy. Sorry, I don’t have enough info on this for you. You can ask your doctor about this and they might be able to help you out. Thanks, Bansah1
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