herpes medication

[kdh]

I have HSV2 and my partner does not.  I have been taking Acyclovir twice a day in order to reduce the risk of transmission (among taking other precautions as well).  My questions are:

1) Is Acyclovir as effective as Valtrex in reducing transmission?  This site stated it might be but obviously I want what's going to work best.

2) How long does the medicine take to start working in terms of reducing the risk?  Does it have to build up for a while before it starts working?

3) Are there any special precautions or instructions when taking this med?  Any crazy side effects?  (I'm getting it from Planned Parenthood and they've been wrong about a lot when it comes to herpes so I want to make sure it's as safe as they tell me)

Thank you so much for your help!

[H. Hunter Handsfield, M.D.]

Good questions.  My first comment is to ask how you know your partner is not infected.  If you're going by symptoms, it isn't sufficient and he (or she) should have a type specific blood test to know for sure.  If positive, you don't need to worry about transmission at all.  But, assuming s/he isn't infected:

1) My guess is that acyclovir works just about as well as valacyclovir (Valtrex) in preventing transmission, but in the absence of data it is impossible to know for sure.  When preventing transmission is the main goal, I routinely prescribe valacyclovir 1.0 gram (not the officially recommended 500 mg) once daily.  Once a day is more convenient (and therefore less likly to result in missed doses) than twice daily, and even at that dose really is not that much more expensive than acyclovir.

2) Efficacy is immediate, as soon as the drug is absorbed into the bloodstream.

3) All the antiherpes drugs (acyclovir, valacyclovir, famciclovir) are extremely safe with virtually no side effects.  In all the clinical trials, even trivial stuff like headache, minimal GI upset, and so on were no more common than for placebo.  Of course, atypical (e.g. allergic) reactions can occur with any drug, but even these appear to be very rare.

Good luck--  HHH, MD

[HHH,MD]

I need to clarify my statement about immediate efficacy.  If you happened to have a herpes outbreak or asymptomatic shedding when you started the drug, it would take 2-3 days before viral replication was stopped.  So for greater assurance, it would be safest to assume it takes 3 days.

HHH, MD