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Famvir dose.

Discussion in 'Antivirals, Antibiotics and Immune Modulators' started by Ema, Dec 21, 2014.

  1. Ema

    Ema Senior Member

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    I'm switching from Valcyte to Famvir for a while due to possible peripheral neuropathy.

    What's the most typical dosage used now? I've seen amounts all over the map from 250 once to 500 three times a day. I swear I read somewhere that it was dosed like Valtrex at 1 g four times a day but I can't find anything definitive.

    What do you all take?
     
  2. Gingergrrl

    Gingergrrl Senior Member

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    @Ema I take 500 mg of Famvir 3x/day (so 1500 mg total for the day.) I have never taken Valtrex, Valcyte or any other anti-viral. I have had people tell me that I am taking a high dose of Famvir and others tell me that I am taking a very low dose! So, I really am not sure but this is what was recommended for me by my doctor.
     
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  3. Ema

    Ema Senior Member

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  4. leokitten

    leokitten Senior Member

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    It's true you should be taking high dosages and frequently in order to really win the battle against EBV etc. I take 1g 3 x day (3g total) and have been doing this for well over a year non-stop. My EBV titers which were originally VCA IgG 1:5120 and EA IgG >1:640 have come down quite significantly.

    Famvir and Valtrex like I believe all nucleoside analogs have very short half lives and you need to keep a constant high enough concentration of the drug to effectively inhibit viral replication and this needs to be done non-stop for a very long time in order to slowly reduce viral load.
     
    Last edited: Dec 21, 2014
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  5. Ema

    Ema Senior Member

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    I think it's a high dose by the standard of how it is typically prescribed for other conditions but it seems to be a moderate dose for ME/CFS.
     
  6. heapsreal

    heapsreal iherb 10% discount code OPA989,

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    Nothing written in stone but valtrex famvir frequency is several times a day I believe because they are indicated for fast replicated viruses like shingles, cold sores and genital herpes.

    I haven't been unable to find the answer but would like to know if ebv/cmv/hhv6 are fast replicators or slow?? At a guess I would think that they aren't as quick as shingles etc. This could be why many do OK with less frequent dosing. I think finding the answer to speed of replication is key to best dosing frequency.

    Another quandary I have come across with dosing is half lives of antivirals. Looking into famvir I found that the half life is approx 4hrs or there abouts. What I also found was that famvir has an intracellular half life of 18hrs. So I'm not really sure what to judge of these 2 half lives? ?

    Also one dosing schedule used for cold sores and genital herpes is a large one off dose of 1500mg. Why does 1 dose work??

    my experience is that 250mg twice a day was enough and lowered my viral load. I have tried 500mg twice a day but didn't notice a difference. But going by most who have used famvir successfully, 500mg twice a day seems the average.

    Using both valtrex and famvir would be interesting, you would think they would both be synergistic. I have used both but only for very short periods so can't tell if it helped more or not. If it's affordable it would be interesting to try more long term.

    There doesn't seem to be much info I guess because it's an off label use.
     
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  7. minkeygirl

    minkeygirl But I Look So Good.

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    When I take more than 250 x 2 I spread it out, mostly because I can't take 500 mgs at one time. It causes a lot of pain and I felt sick on it.

    I had been at 250 x2 but when I had a stress reactivation I upped it to 1000 mgs and it really helped pull me out of the crash. I'm backing down to 750 again so I have some place to go if I have another reactivation. Maybe I need to do more of what leokitten is doing and stop the crash to start with?

    @heapsreal, I can't take Valtrex, side effects are too horrible. Are Famvir and acyclovir too closely related to double up with them? What do you think about oxymatrine?
     
  8. leokitten

    leokitten Senior Member

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    The required frequency and dosage of a drug have nothing to do with whether a virus is a fast or slow replicator. Fast or slow replication is one of the factors that would affect how long it takes to bring viral load down at a steady concentration of drug. With drugs that inhibit growth/replication it is extremely important to maintain a steady concentration of drug.

    For each antiviral after some digging you will find the minimum steady concentration of the drug to inhibit 50%, 90%, and 99% viral replication.

    The half-life of both famiciclovir and penciclovir are just over 2 hours. So very short and the only one that matters is penciclovir since it is the active drug, famiciclovir is just a prodrug.

    Penciclovir has a long intracellular half-life but that shouldn't change dosing frequency and amount because it has weaker viral activity than Valtrex's active drug acyclovir and therefore requires higher intracellular concentrations.

    Valtrex and Famvir would make no sense to use together, they would not be synergistic at all and would compete against each other because they have the exact same target.
     
  9. heapsreal

    heapsreal iherb 10% discount code OPA989,

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    @leokitten you say a steady state of the drug is required to inhibit growth and replication but there are several abx that have very short half lives of a few hours which are dosed twice a day which are effective. Also with valcyte dosing, during different times of the course of treatment the drug is either given twice a day and even once a day. Valcyte has a 4hr half life so dosing once or twice day the steady state is out the window but the drug is effective. Going by what your saying than valcyte should be dosed 4hrly. I would assume there is more to just a steady state. Also a steady state and blood levels do build up to a certain level overtime of a few days. Your correct in that famvir half life is 2hrs not 4hrs but I pulled that figure out of my pocket as a guess or approximation. The main reason it was even mentioned was only to compare it to the much longer intracellular half life.

    so your statement of valtrex and famvir working the exact same way is null and void when u take into the account of doctors being guided into switching patients showing viral resistance to valtrex and putting them on famvir. If they truly were the same then this recommendation wouldn't have been made. Maybe they need to relable all the boxes the same. Oh but valtrex u said was stronger, maybe label it valtrex forte.

    so if famvir has an intracellular half life of 18hrs, ,why would one need to dose it more than twice a day? Seems like a waste.

    why would the speed of replication not be a factor of a virus and it's treatment. In combination with half lives of drugs this would be important. One needs to marry up the frequency of viral replication to make sure there is enough antiviral in the body to have an effect.

    I wouldn't say valtrex is stronger than famvir, maybe for different viruses but anecdotally famvir seems to work more efficiently for many viruses that causes issues for cfs. My personal experience and from others on this forum shows that they get better response from famvir for ebv/cmv/hhv6. When I use valtrex only all I get is increased viral symptoms and increase in lymphocytes and cd8 t cells, which says to me valtrex isn't cutting it. But on my paltry dose of weak famvir twice a day is enough to knock this virus back wards.

    Also famvir is regarded as the antiviral of choice over valtrex for shingles infections. As you have stated valtrex is the pro drug of acyclovir which as been around much longer, research is showing more viral resistance to acyclovir and it's recommend when this happens to change the patient to famvir. so because the above situation is recommended in many medical books ,there's a possibility of being some synergy, but it's all speculation.

    If what your saying was true about famvir and valtrex having the same target than this would also make it invalid to use valcyte with either famvir or valtrex ,as valcyte was designed from acyclovir.

    The point of using valtrex and famvir together is we don't really know if there is a synergistic effect ebv/cmv/hhv6 but if cost wasn't a problem, I assume they would be safe together as either of them have been combined with other drugs as well as valcyte.

    Due to financial reasons, many can't afford to take large dose multiple times a day so have used lower doses twice a day and improved. These doses are very similar to suppression therapy used in genital herpes infections as well as organ transplant prophylaxis for cmv. Again the steady state drug levels don't seem to apply here.
     
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  10. lansbergen

    lansbergen Senior Member

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    Anything known about metabolites? With the immunemodulator I use there is at least one metabolite far more potent than the parent molecule.
     

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