How do the current herpes medications (pills) work?
Mode of Action
The major drugs that doctors use to treat the herpes simplex virus (HSV) are antiviral agents called nucleosides and nucleotide analogues. They work by blocking reproduction of the herpes simplex virus. These drugs are oral medications called acyclovir, valacyclovir and famciclovir. There are other antivirals similar to these drugs that are available in topical and intravenous formulations, but they are generally used to treat different viruses.
Acyclovir, Valacyclovir and famcyclovir can lessen the severity of a primary outbreak, reduce the time it takes genital herpes outbreaks to heal and can decrease the number of days of symptoms and days the virus is transmissible.
These antiviral medications are most effective when taken early in the course of an outbreak, when you first feel the tingling and pain. If you have a lot of outbreaks (more than 6 a year), studies show that taking antiviral medication daily to suppress the virus can reduce the frequency and duration of recurrent outbreaks.
What Prescription Herpes Tablets are available?
Acyclovir (also known as Aciclovir or Zovirax)
This was the first prescription pill introduced for genital herpes. The brand name for this drug is Zovirax, however, it is now a generic and as a result is the cheapest out of all three herpes medications. Acyclovir has been approved for the treatment of initial and recurrent genital herpes episodes.
Acyclovir needs to be taken the most frequently out of all of the herpes medications, but is the least expensive. It should be taken no less than 3 to 5 times a day to be effective. Like all of the herpes medications, it should be started at the first sign of symptoms, such as tingling or itching, to be most effective.
Valacyclovir’s brand name is Valtrex. It is a prodrug of acyclovir, which means that it converts into the active drug acyclovir once inside the body and is utilized and absorbed more efficiently. This doesn’t make this drug more effective than acyclovir, it just means you need to take less of it to achieve the same result.
Valtrex has been approved for the treatment and suppression of genital herpes. This means that it can be prescribed as a daily medication to help stop outbreaks from coming back. However, it is normally only prescribed in this way if the outbreaks are very frequent, such as 6 or more per year. The majority of people will be prescribed to take Valtrex only when they are experiencing symptoms.
To prevent an outbreak happening Valtrex is usually taken once daily. When it is used to treat the active symptoms only, a less concentrated dose of 2 tablets per day can be prescribed for 3 to 10 days. Once again, the course should be started within the first 24 hours of noticing any signs or symptoms to be effective.
Famcyclovir’s brand name is Famvir. It is a prodrug of a different antiviral called penciclovir, which is very similar to Valacyclovir. Famcyclovir has been approved for the treatment and suppression of genital herpes, however, its efficacy has not been established in regards to treatment of the first initial outbreak. It can be prescribed as a daily medication to help stop outbreaks from coming back, however, it is normally only prescribed in this way (as a suppressive) if the outbreaks are very frequent, such as 6 or more per year.
Famcyclovir needs to be taken the least frequently out of all of the herpes medications, but is more expensive. It should be taken no less than two times a day to be effective for genital herpes, but only once a day for cold sores. Like all of the herpes medications, it should be started at the first sign of symptoms, such as tingling or itching, to be most effective.
Do they all work the same?
Effectiveness and Dose
Current research has not found any major differences in the safety or effectiveness of these three antiviral drugs. All three medications can be taken at the first sign of an outbreak, or taken daily to help suppress the virus and prevent a recurrence of symptoms.
There is limited data on how effective famciclovir is during the first primary outbreak, and for this reason acyclovir or valacyclovir are normally prescribed during the first genital herpes outbreak.
Valacyclovir (Valtrex) needs to be taken less often than Acyclovir because it is absorbed more efficiently by the body. This makes it more convenient but it is also more expensive. Valacyclovir is the only one of these three medications that has been proven to reduce the rate of transmission to an uninfected partner, if taken daily. Valacyclovir may help to reduce the incidence of Viral Shedding by approximately 40%.
Famcyclovir is generally the most convenient of the three medications because it needs to be taken least often, but typically has the highest price tag.
All of the medications are generally safe in most circumstances but may occasionally have adverse side-effects. To help reduce any side-effects the medication should be taken along with food and will likely reduce with each successive dose.
Many people do not experience any side-effects, and they are most common when taking the medication daily as a suppressive. These side-effects are normally not severe and could include nausea, diarrhea, headache, stomach aches, flu symptoms or sore throat.
More severe side-effects such as alopecia (hair loss) and seizures have been reported but are rare. You can see a full list of these below. People with kidney disease are normally put on a reduced dose which is monitored closely by a physician. All three medications will normally only be prescribed during pregnancy if the potential risk to the foetus outweighs the benefit of taking the medication, as the safety of these medications during pregnancy has not been established.
Have a look at our Herpes Treatments Page to compare the difference in dose, price and effects of these drugs.