So you've made the decision to go on suppressive therapy with either acyclovir, valtrex or famvir. Perhaps it's to protect a partner or perhaps it's to reduce the number of ob's you have. You've done your homework and you've even perhaps taken the time to read the full prescribing info on the medication you chose too. Or perhaps you've talked to your doctor about it all and they've told you you can only stay on it for a year. So now what?
When drug companies apply for FDA approval, they typically only do it once. So if the original studies only backed the safety of something for 1 year, they will say that it's safety has not been evaluated for more than 1 year. Not many companies are going to pay again for research to be able to say it's safer longer nor are they going to go for fda approval to say otherwise. So how do you find out if it's ok to stay on suppressive therapy longer? Well with every drug ( and vaccinations too ) , any side effects post marketing are reported to the FDA and the drug company. You'll even see this listed on most prescribing info nowadays specifically this way. There are also pregnancy registries for most drugs too. The generally accepted medical practice is - nothing reported as an issue by a decent amount of folks then assume it's safe. Not always the best but the reality is there isn't the time or the money to do better with all the various medications out there.
So back to herpes antivirals. Should you be worried if you decide to take them for longer than 1 year? Absolutely not! There are no known long term effects to taking them. Acyclovir even almost went otc at one point - the main reasons it didn't was because it was feared that folks who could afford it because of their insurance would no longer be able to as well as the fear that self treating would result in folks not getting properly tested and syphilis being missed and self treated as herpes. There is a terrific article by Dr Stephen Tyring that you can access for free online to read that I highly recommend - http://www.journals.uchicago.edu/doi/pdf/10.1086/342966?cookieSet=1 It addresses why long term use of valtrex is thought to be just as safe as long term use of acyclovir ( acyclovir has been on the market way longer than valtrex though valtrex is an acyclovir prodrug ). It's an excellent article if you've never taken the time to read it before. Also be aware that there's no need for any bloodwork to be done either if you are on antivirals long term. They do not damage your kidney's or your liver.
If you have any questions - feel free to post them on the herpes forum - http://www.medhelp.org/forums/Herpes/show/195