Type of medicine Antiviral
Used for Herpes zoster (causes shingles)
Herpes simplex (causes cold sores, genital herpes)
Prevention of cytomegalovirus disease following renal transplant
Also called Valtrex
Available as Tablets

Valtrex is known as a pro-drug. Once inside the body it is broken down into the active ingredient aciclovir. Aciclovir works by blocking the action of DNA polymerase, therefore preventing the herpes viruses from multiplying.

Why is this drug prescribed?

Valtrex tablets contain the active ingredient valaciclovir. Valaciclovir is known as a pro-drug. Once inside the body it is broken down into the active ingredient aciclovir, which is an antiviral drug used to treat infections with herpes viruses. These include the viruses that cause cold sores and genital herpes and the virus that causes chickenpox and shingles. Aciclovir works by stopping these herpes viruses from reproducing and infecting more cells in the body. Aciclovir is converted to a more active form inside cells of the body that are infected with herpes viruses. The activated aciclovir then works by blocking the action of a viral enzyme called DNA polymerase. The herpes viruses need the DNA polymerase enzyme to copy their genetic material from RNA to DNA. This process is necessary for the viruses to multiply and continue to survive. By blocking the action of DNA polymerase, aciclovir prevents the herpes viruses from multiplying. This controls the infection and helps the immune system to deal with it. Valaciclovir is taken by mouth to treat herpes infections that cause shingles. It is also taken to treat herpes simplex infections of the skin and mucous membranes, including genital herpes. Valaciclovir can be used to treat recurrent flare-ups of herpes simplex infection. It is most effective at preventing the sores from developing if treatment is started as soon as the warning signs appear. If you suffer from frequent herpes simplex flare-ups your doctor may prescribe valaciclovir for you to take regularly, to suppress the virus and prevent recurrences. Valaciclovir taken regularly can also reduce the risk of passing the genital herpes to a sexual partner, provided safe sex practices such as condoms are used as well. However, you should still avoid sexual contact when the sores are present to avoid passing on the virus. Valaciclovir has a further use in preventing infection with cytomegalovirus in people who have had a kidney transplant. CMV is another member of the herpes group of viruses. In healthy people this common virus normally produces symptoms milder than the common cold, but in people whose immune systems are compromised it can cause serious infection because the immune system cannot fight it. People who have had kidney transplants are given powerful drugs that suppress the immune system in order to stop it attacking the transplanted organ. However, because they suppress the immune system, these drugs also suppress the ability of the body to fight infection. Valaciclovir is therefore given to people who have received a kidney transplant, in order to help the body kill off any CMV virus.

Treatments

* Genital herpes * Herpes simplex infections of the skin, eg cold sores * Preventing recurrence of herpes simplex infections, eg recurrent cold sores or genital herpes * Reducing the risk of spreading genital herpes to a sexual partner * Prevention of cytomegalovirus infection in people who have had a kidney transplant * Shingles

What side effects can this drug cause?

* Headache * Abdominal pain * Diarrhoea * Drowsiness * Confusion * Abnormal reaction of the skin to light, usually a rash * Decreased kidney function * False perceptions of things that are not really there * Dizziness * Nausea and vomiting * Decrease in the number of platelets in the blood * Skin reactions such as rash and itch * Disturbances of liver function