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Differences between Valtrex and acyclovir

Active Ingredients

Valtrex (Zelitrex, Valaciclovir, Valacyclovir) is a prodrug, which gets transformed into acyclovir in the body. Acyclovir is also known as Aciclovir, acycloguanosine, ACV, Cyclovir, Herpex, Acivir, Acivirax, Zovirax, Aciclovir, and Zovir. Both of these medications are used to treat the symptoms of herpes simplex and herpes zoster infections in the body. So, these medications contain different active ingredients. Acyclovir contains acyclovir and Valtrex contains Valacyclovir (the prodrug of acyclovir).


Acyclovir is usually prescribed as 200, 400 or 800mg tablets. Patients suffering from herpes zoster usually have to take 800mg of acyclovir, 5 times a day, for 7 to 10 days. Genital herpes is treated with 200mg dose, every 4 hours of the day, also for 10 days.

Valtrex can be found as 500mg or 1g tablets. Cold sores are treated with 2g of Valtrex, 2 times for one day. Genital herpes requires 1g, 2 times a day, for 10 days. Recurrent genital herpes is treated differently – the therapy lasts for 3 days and the patient should use 500mg of Valtrex, 2 times a day.


The difference between acyclovir and Valtrex is in the condition they are prescribed for. While Valtrex is used to treat regular herpes virus infection, acyclovir is usually the option for recurrent infections. This shouldn’t be understood as the rule, because doctors can prescribe any of these medications whenever they think it is necessary.

Adverse Effects

Valtrex patients might experience side effects such as nausea, vomiting, diarrhea, tiredness, fever pains, and headaches. In rare cases, people using Valtrex could get aggressive or confused, and experience vertigo, dizziness, abdominal pains, edema, joint pain, constipation and kidney problems. Extremely rarely, there were reports of tremor, anorexia, psychotic and anaphylactic reactions to the medication, severe skin and blood problems, hepatitis and coma.

Acyclovir has more or less similar side effects as Valtrex. Intravenous acyclovir therapy can provoke nausea, vomiting, headaches and diarrhea. Rarely, acyclovir could lead to reactions on the injection site, vertigo, anxiety, confusion, tiredness, abdominal problems and edemas and joint pain. High doses of this medication may cause hallucinations and kidney problems. In less than 0.1% of the patients receiving intravenous acyclovir, there were hepatitis, blood-related problems, seizures and coma.

Acyclovir cream could cause skin irritation, itching and redness.

Acyclovir used in eye treatment can be a painful experience for the patients, and in some cases may cause allergy or keratitis.


Patients using Valtrex should not operate the machinery or drive, because the medication might cause them to feel dizziness. Valtrex should not be used in elderly patients, since they might be sensitive to this medication and suffer from excess confusion, anxiety and kidney problems. Pregnant women should consult the doctor about the use of this drug. Breast feeding mothers should know that Valtrex passes into the breast milk and should always consult their doctor before starting the Valtrex treatment.

Acyclovir should also be avoided in pregnant women. It is known to be a mutagen agent, but because it didn’t show effects to the unborn children, many pregnant women use this drug. Before the therapy, inform your doctor about the pregnancy and consult him/her about the possible consequences of the acyclovir treatment. Patients suffering from kidney problems have higher risk of developing side effects such as confusion, lethargy or sudden muscle twiches.

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