What Is Valacyclovir Hydrochloride?

B. Chisholm

Valacyclovir hydrochloride is an antiviral drug used to treat cold sores, genital herpes, chicken pox and shingles. It is used orally and the dose and duration used depends on which indication it is being used for. In most countries it is available by prescription only and may be known by different trade names, according to manufacturer.

Cold sores can be treated with valacyclovir hydrochloride.
Cold sores can be treated with valacyclovir hydrochloride.

The way in which valacyclovir hydrochloride works is by blocking a viral enzyme called DNA polymerase, which is essential for viral DNA replication. Valacyclovir hydrochloride is actually a prodrug of aciclovir. This means that, when it enters the body it is broken down into the active substance, aciclovir. Its advantage is that it can be taken two to three times a day, whereas aciclovir must be taken up to five times a day, making adherence more difficult.

Valacyclovir hydrochloride is often used to treat chickenpox.
Valacyclovir hydrochloride is often used to treat chickenpox.

Herpes Simplex infections, which include cold sores and genital herpes, are incurable, but may go through periods of remission. Valacyclovir hydrochloride is used in both the treatment of acute cases and for chronic suppression in people who have recurrent episodes. It is usually only given long-term to people who have more than six episodes of herpes or more in a period of a year and chronic treatment should be reassessed every six to twelve months. The dose for treatment of an acute episode is usually higher and is for a short period, usually up to 10 days.

Chickenpox is a common childhood disease and is usually caused by Varicella zoster. Shingles is more common in adults, can be extremely painful, and is caused by the virus Herpes zoster. Valacyclovir hydrochloride is active against both of these viruses but treatment needs to be started early to see results. It should be started within 24 hours of the appearance of the rash and is usually given three times daily for five days with chickenpox and seven days with shingles. The pediatric dose is determined by weight and the prescribed dose and duration of treatment should be followed precisely.

As with any medication, valacyclovir hydrochloride may interact with other drugs so these, including over-the-counter, homeopathic and natural medicines, should be discussed with the prescribing doctor. Pregnancy, desired pregnancy and lactation should also be disclosed. Adverse effects may also occur during treatment with valacyclovir hydrochloride. The most commonly seen adverse effects include headache, nausea, vomiting, diarrhea and dizziness. Should any of these be severe, medical attention should be sought immediately.

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