Can anyone tell me what the difference is between the herpes meds; why does a doctor prescribe one drug over the other -- acyclovir valtrex or famciclovir (Famvir)?

It really doesn't matter that much. Some medications are used more frequently than others because of a few different factors. Some doctors prefer prescribing medication that has been around longer (acyclovir has been around many years before Valtrex came out). Other doctors do it for insurance reasons and the cost of the medication (Valtrax is more expensive than acyclovir or famciclovir). Also, Valtrex is the ONLY herpes medication proven to HELP reduce the spread of herpes. It does not PREVENT it, but it helps prevent the spread of it. Acyclovir is also the recommended antiviral for suppressive therapy to prevent transmission of herpes simplex to a neonate.

I personally take acyclovir when I have a herpes outbreak. But, during my first outbreak I was prescribed acyclovir, famciclovir, and acyclovir ointment.

I guess it all just depends on what your doctor thinks would be better for you and how much you want to spend on the medication. Personally I think the med they prescibe are fake and non-effective, just another way to get money for the large profitable medical market. I've been taking L-Lysine and Zinc for 3 years now and rarely to zero have had any outbreaks or shedding symptoms...and I've never been to the docotor, so I don't think they work, the vitimans I take work just fine for me. Well acyclovir is less expensive and is usually the first medication subscribed.