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Valtrex vs. Acyclovir

Discussion in 'Antivirals, Antibiotics and Immune Modulators' started by Christopher, Oct 9, 2013.

  1. Christopher

    Christopher Senior Member

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    I found this helpful info. when researching differences between the 2 drugs.

    Valacyclovir has three to fivefold greater oral bioavailability (about 55 percent) than acyclovir; it then undergoes rapid and extensive first-pass intestinal and/orhepatic hydrolysis to yield acyclovir and L-valine [2,3]. Food does not affect absorption.
    Valacyclovir, at a dose of 250 mg four times daily, generates essentially the same acyclovir AUC (area under the curve, or exposure over 24 hours) as oral acyclovir at a dose 800 mg five times daily [3]. Valacyclovir, at a dose of 1000 mg three times daily, produces a similar acyclovir AUC as intravenous acyclovir at a dose of 5 mg/kg every eight hours [4]
    http://www.uptodate.com/contents/valacyclovir-an-overview

    So if you do well on a dose of 500mg/once a day (like I do), you would need multiple doses totaling to 2000mg to achieve a similar effect. I'm not sure if the valtex still isn't better because you're getting a more steady dose of it over time vs. the acyclovir.
  2. SOC

    SOC Moderator and Senior Member

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    This is why most docs don't use oral acyclovir anymore (except as a placebo;)). Valacyclovir is the improved (for oral administration) version of acyclovir, not really a completely different med. Oral valacyclovir converts to acyclovir through a process I know nothing about in a way that makes it much more bioavailable. So less Valtrex taken less often gives the same effect as more acyclovir more often. Why use oral acyclovir, which puts more med into your body to less effect, unless cost is a major obstacle or you want to give a uselessly small dose to make your patient feel like you're doing something when you're not?

    Okay, maybe I'm exaggerating a little. ;) I think docs will use oral acyclovir when they think the infection is not serious and the weaker, cheaper med at low dosage is sufficient. Also, if the doc wants really high dosage of acyclovir, then giving IV acyclovir gets more into your blood (and therefore your body systems) than any oral form of the med -- oral acyclovir or Valtrex.
  3. SOC

    SOC Moderator and Senior Member

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    Christopher, what virus are you treating successfully with that low dosage of Valtrex?
  4. vamah

    vamah Senior Member

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    I found acyclovir effective at keeping low level herpes 1 infection in check. Stopped getting cold sores after starting it. Don't know if it is useful for much else.
    SOC likes this.
  5. Christopher

    Christopher Senior Member

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    Dr. Levine prescribed it for somewhat high EBV and HHV-6, but not the high levels I've heard of. My neurological symptoms improve while I'm on it, but if I stop taking it, they recur.

    I'm not sure what it's doing honestly, but it's a good thing.
  6. vamah

    vamah Senior Member

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    I had a similar experience with acyclovir. I didn't really notice any change in symptoms when I was on it, but I definitely felt worse if I went off. Ultimately, if I have EBV, it may have helped with that. But did nothing for hhv6, as my levels were extremely high even after taking for several months.

    Might be the same for you. It helps suppress your EBV so you feel a bit better. Ultimately, though, if you have hhv 6, I think you will have to start a better antiviral.
    SOC likes this.
  7. SOC

    SOC Moderator and Senior Member

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    I wouldn't argue with symptom improvement. :D
  8. Creekee

    Creekee Senior Member

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    Do you get a reaction when you start acyclovir? After recent abx startups :sluggish:, I'm feeling gunshy.

    Fwiw, my provider is using acyclovir as a test of antivirals because it's covered by my insurance. If it seems to do anything positive, we'll look at a more aggressive antiviral. But I'll probably have to pay out-of-pocket for anything else.

    :cry:

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