Acyclovir vs Valacyclovir - Differences and Similarities

This page contains information on two medicines, acyclovir vs valacyclovir (Valtrex), used to treat skin conditions caused by the herpes virus and herpes zoster. Here you can find out about valacyclovir vs acyclovir: their usage, dosage, drug interactions and potential side effects.

Valacyclovir vs acyclovir are prodrugs. They work by inhibiting the replication of viral DNA which is necessary for viruses to reproduce themselves. On consumption the two medicines convert into an active substance working quickly to prevent further spread of infection to healthy cells in the body. Aciclovir is available as a topical, oral and intravenous medication. Valacyclovir is active against the same viruses as acyclovir, but has a longer duration of action and therefore, can be taken fewer times each day.

Acyclovir vs valacyclovir: usage

Oral Aciclovir is used for treating genital herpes, shingles and chickenpox. It reduces the pain and the number of lesions in the initial case of genital herpes, and decreases the frequency and severity of recurrent infections. When used to treat shingles, it can lessen pain while significantly reducing the healing time. This medicine also limits the spread of virus and the formation of new lesions.

Valaciclovir is an oral antiviral drug used to contain and eliminate the herpes viruses. It is used to treat infections caused by the herpes zoster herpes simplex, and herpes labialis.

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Acyclovir vs valacyclovir: dosage

Aciclovir may be taken with or without food. The usual prescribed oral doses are 200mg to 800mg every four hours,five times per day. The usual adult intravenous dose is 5-10 mg/kg every eight hours for one full week. Valaciclovir may be taken with or without food also. For the treatment of shingles, the usual dose is 1 gm three times a day for one full week. Treatment should begin at the initial symptoms, and used within 48 hours of the onset of rash. When used by patients who have kidney disease the dosage should be reduced.

Acyclovir vs valacyclovir: drug interactions

There are certain precautions you should be aware of when using these medicines. Aciclovir may reduce levels of phenytoin or valproic acid. Probenecid may increase aciclovir serum levels by decreasing renal excretion of acyclovir. Acyclovir may increase serum levels of theophylline.

Probenecid and cimetidine may reduce the kidney's clearance of valacyclovir, leading to higher concentrations in the blood. This may lead to side effects of valacyclovir.

If you are worried about how the treatment may interact with a medication you may be taking, prescription or otherwise, please consult your doctor or take an online consultation with a registered doctor from an online clinic.

Acyclovir vs valacyclovir: side effects

As with many prescription medications, acyclovir vs valacyclovir are not without side effects.

The most common side effects are nausea, vomiting, diarrhoea and headache. Other reported side effects from participants in clinical trials have included agitation, confusion, rash, anemia, and muscle pain. Hypersensitivity reactions, seizures, agitation, confusion, anemia, hepatitis, and muscle pain have also been reported by a small number of users.

The side effect profile of valacyclovir is similar to that of acyclovir. Common side effects are headache, nausea, and vomiting. Few people may experience diarrhoea, abdominal pain, and dizziness when using this medication.