Valtrex tablets contain the active ingredient, valaciclovir and are used to treat infections with the herpes virus. The herpes viruses include the viruses that cause cold sores and genital herpes (herpes simplex 1 and 2)
Valaciclovir works by stopping the herpes virus from reproducing and infecting more cells in the body. It is converted to a more active form inside the infected cells of the body. The activated valaciclovir then works by blocking the action of a viral enzyme called DNA polymerase thus preventing the virus from multiplying. This controls the infection and helps the body’s immune system to deal with it.
Valaciclovir is taken by mouth to treat genital herpes and other herpes simplex infections of the skin and mucous membranes. 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.
Oral valaciclovir is also valuable for preventing herpes simplex infections in people whose immune systems are suppressed and cannot fight off infection, either due to disease, e.g. HIV and AIDS, or medical treatment, e.g. chemotherapy, steroids, bone marrow transplant.
Adults should use the following regimens for the treatment of a herpes simplex infection:
- For the first episode one 500mg tablet twice a day for 5 to 10 days
- For recurrent episodes one 500mg tablet twice a day for 3 to 5 days
- One 500mg tablet a day for 6 to 12 months
If your immune system is severely impaired or you have impaired absorption from the gut, the dose may need to be increased. If this is the case please consult a doctor.
Medicines and their possible side effects can affect individual people in different ways. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect. The following are some of the side effects that are known to be associated with valaciclovir:
Common (affect between 1 in 10 and 1 in 100 people)
- Feeling sick.
- Skin reactions such as rash, itching, or increased sensitivity of the skin to sunlight (photosensitivity).
Uncommon (affect between 1 in 100 and 1 in 1000 people)
- Abdominal discomfort.
- Nettle-type rash (hives or urticaria).
- Shortness of breath.
- False perceptions of things that are not really there (hallucinations).
- Kidney pain (felt in the lower back) or blood in the urine. Tell your doctor if you experience this as it could be a sign of a problem with your kidney function.
- Disturbances in liver function.
- Decrease in the number of platelets in the blood (thrombocytopenia).
- Decrease in the number of white blood cells in the blood (leucopenia – mainly in people with a weak immune system).
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with valaciclovir, please read the information provided with the medicine or consult your doctor or pharmacist.
Genital herpes is a sexually transmitted disease. The risk of passing the infection on to your sexual partner is greatest when you have active symptoms of the infection. There is still a risk of passing the infection on if you use condoms, and even if you are taking this medicine to help control the infection.
It is therefore important that you avoid having sex while you have symptoms, even if you are taking this medicine to treat the infection.
Valaciclovir should be used with caution in:
- Elderly people.
- Decreased kidney function.
- People with a liver disease.
- People with a lowered immune system.
Valaciclovir should NOT be used in:
- Allergy to aciclovir or valaciclovir.
This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using valaciclovir and inform your doctor or pharmacist immediately.
The patient information leaflet (PIL) is a leaflet containing specific information about medical conditions, doses and side effects. You can download a copy of the PIL here:
Patient Info Leaflet