Q: What are the effects of Valtrex?
A: The pharmacologic effects of Valtrex (Zosvir) vary depending on the indication for use. Valtrex is an antiviral medication indicated for the treatment and control of infections caused by herpes viruses in adults and children, including genital herpes, cold sores, shingles and chickenpox. The pharmacologic effects of Valtrex for all indications appear to be a result of the inhibition of viral replication. During clinical trials for shingles (herpes zoster), in adults with healthy immune systems, the effects of Valtrex appeared to shorten the time to cessation of new lesions by 1 day as compared to placebo in patients younger than 50 years of age. All patients were treated with Valtrex within 72 hours of the onset of rash. Two placebo-controlled clinical trials were conducted to evaluate the effects of Valtrex in adult and adolescent patients, 12 years of age and older, with a history of recurrent cold sores. The results of these studies demonstrated the effects of Valtrex, administered for one day, shortened the average duration of a cold sore episode by approximately one day. The majority of patients in these studies initiated treatment within 2 hours of the onset of symptoms. During clinical trials for the initial episode of genital herpes infections, in adults with healthy immune systems, the effects of Valtrex included a median time to lesion healing of 9 days, a median time to cessation of pain was 5 days and a median time to cessation of viral shedding was 3 days in patients treated for 10 days. Patients were administered Valtrex within 72 hours of the onset of symptoms. For adult patients, with healthy immune systems, with recurrent episodes of genital herpes, the effects of Valtrex demonstrated in clinical trials indicated a shortened median time to lesion healing and cessation of viral shedding by 2 days and a shortened median time to cessation of pain by 1 day. While the effects of Valtrex differ slightly depending on indication for treatment, overall, the effects of Valtrex to inhibit viral replication appears to shorten the duration of the infection.
Following oral administration of a 500-mg dose of VALTREX to 5 nursing mothers, peak acyclovir concentrations (Cmax) in breast milk ranged from 0.5 to 2.3 times (median 1.4) the corresponding maternal acyclovir serum concentrations. The acyclovir breast milk AUC ranged from 1.4 to 2.6 times (median 2.2) maternal serum AUC. A 500-mg maternal dosage of VALTREX twice daily would provide a nursing infant with an oral acyclovir dosage of approximately 0.6 mg/kg/day. This would result in less than 2% of the exposure obtained after administration of a standard neonatal dose of 30 mg/kg/day of intravenous acyclovir to the nursing infant. Unchanged Zosvir was not detected in maternal serum, breast milk, or infant urine. Caution should be exercised when VALTREX is administered to a nursing woman.
What other drugs will affect Zosvir?
Zosvir can harm your kidneys. This effect is increased when you also use certain other medicines, including: antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including aspirin, Tylenol, Advil, and Aleve).
Other drugs may interact with Zosvir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.
Zosvir is a nucleoside analogue antiviral agent and prodrug of acyclovir which is used in therapy of herpes and varicella-zoster virus infections. Zosvir has been associated with rare instances mild, clinically apparent liver injury.
What is Zosvir hydrochloride?
Zosvir hydrochlor >antiviral prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the following treatment and prevention uses for certain types of herpes simplex virus (HSV) infection :
- To treat initial or recurrent episodes of genital herpes in healthy adults
- To treat cold sores (also known as herpes labialis, orolabial herpes, or orolabial lesions) in adults and children
- To prevent genital herpes outbreaks in adults living with HIV
- To reduce the risk of transmitting genital herpes to other people
Zosvir is a nucleoside analogue DNA polymerase inhibitor. Zosvir hydrochloride is rapidly converted to acyclovir which has demonstrated antiviral activity against HSV types 1 (HSV-1) and 2 (HSV-2) and VZV both in cell culture and in vivo.
The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts acyclovir into acyclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In biochemical assays, acyclovir triphosphate inhibits replication of herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase. The greater antiviral activity of acyclovir against HSV compared with VZV is due to its more efficient phosphorylation by the viral TK.
Zosvir tablets are used in children:
- to treat cold sores (for children ≥ 12 years of age)
- to treat chickenpox (for children 2 to Do not take Zosvir tablets if you are allergic to any of its ingredients or to acyclovir. The active ingredient is Zosvir.
Before taking Zosvir tablets, tell your healthcare provider: About all your medical conditions, including:
- Valtrex may be taken with or without food.
- In people with kidney disease, doses need to be reduced.
- For the treatment of herpes zoster (shingles), the usual dose is 1 gm. three times a day for 7 days. Treatment should begin at the first symptom and is most effective if started within 48 hours of the onset of rash.
- The dose for chickenpox is 20 mg/kg 3 times daily for 5 days (maximum dose is 1000 mg 3 times daily) and treatment should start at the earliest sign or symptom.
- For the treatment of an initial episode of genital herpes, the usual dose is 1 gram (1000 mg) twice daily for 10 days. For the treatment of recurrent genital herpes, the usual dose is 500 mg twice daily for 3 days. For best results, treatment should be initiated within 12 hours of the start of symptoms.
- The dose for cold sores is 2000 mg (2 grams) every 12 hours for 1 day.
- Valtrex showed no effects on the fetus in animal studies; however, there has been no adequate evaluation of Zosvir or (acyclovir) in pregnant women. The incidence of birth defects in women taking acyclovir is about the same as in the general population. Valtrex should only be used during pregnancy when the benefits to the mother outweigh risks to the fetus.
- It is not known whether Valtrex is excreted into breast milk. It is known, however, that among women taking acyclovir, concentrations of acyclovir in breast milk are about four times higher than in the mother's blood. The safety of Zosvir in breastfeeding infants has not been established. Methods other than breastfeeding should be considered if Zosvir must be taken while nursing.
- Oral herpes causes cold sores. These are small, painful sores that you can get in or around your mouth. Cold sores can be spread by kissing or other physical contact with the infected area of the skin.
- Genital herpes is a sexually transmitted disease. This means it’s spread through sexual contact. Symptoms include small, painful blisters on the genital area. You can spread genital herpes to your sexual partner even when you don’t have any symptoms. This drug is used to treat or prevent flare-ups of genital herpes in people with normal immune systems, or in people with HIV.
- Shingles is caused by the same virus that causes chickenpox (varicella zoster). Symptoms of shingles include small, painful blisters that appear on the skin. Shingles can occur in people who have already had chickenpox. It can also spread to people who have not had chickenpox before through contact with the infected skin.
- Chickenpox causes an itchy rash of small, red bumps that can look like pimples or insect bites. The rash can spread almost anywhere on the body. Chickenpox can also cause flu-like symptoms, such as fever or tiredness. This drug is used to treat chickenpox in children ages 2 to18 years who have a normal immune system.
Storage And Handling
VALTREX Caplets (blue, film-coated, capsule-shaped tablets) containing Zosvir hydrochloride equivalent to 500 mg Zosvir and printed with “VALTREX 500 mg.”
Bottle of 30 (NDC 0173-0933-08). Bottle of 90 (NDC 0173-0933-10). Unit dose pack of 100 (NDC 0173-0933-56).
VALTREX Caplets (blue, film-coated, capsule-shaped tablets, with a partial scorebar on both sides) containing Zosvir hydrochloride equivalent to 1 gram Zosvir and printed with “VALTREX 1 gram.”
Bottle of 30 (NDC 0173-0565-04).Bottle of 90 (NDC 0173-0565-10).
Q: What are the long-term side effects of Valtrex?
A: Valtrex (Zosvir) is an antiviral drug that slows down the spread of the herpes virus. Valtrex will not cure the herpes virus but Valtrex will lessen the symptoms of the infection. Valtrex is used for the herpes virus which includes genital herpes, cold sores, chicken pox and shingles. Valtrex can be taken with or without food. Treatment with Valtrex should be started as soon as the first appearance of symptoms. Valtrex is more effective if taken within 1-2 days after the symptoms start. Take Valtrex with a full glass of water. Water is very important when taking Valtrex so the kidneys keep working effectively. Common side effects of Valtrex include nausea, stomach pain, headache, dizziness, and possibly a mild skin rash. Valtrex may cause dizziness which may be made worse if used with alcohol or certain medicines. Talk to your doctor if your experience serious side effects such as increased thirst, loss of appetite, swelling, weight gain, shortness of breath, feeling shaky, or problems with speech or vision. Kimberly Hotz, PharmD
What is the dosage for Valtrex (Zosvir)?
Q: Can Valtrex cause hypertension?
A: Hypertension has been reported in less than 1% of studied patients taking Valtrex (Zosvir). Please talk with your physician about questions regarding your prescription medications and possible associated side effects. Click here for additional information provided by Everyday Health regarding high blood pressure. Jen Marsico, RPh
Mechanism of Injury
After absorption, Zosvir is converted to acyclovir by the liver, which is metabolized intracellularly in viral infected cells and is excreted largely unchanged by the kidneys. Zosvir is not activated in cells without viral kinases, perhaps accounting for the absence or rarity of hepatic injury.
Is Valtrex (Zosvir) safe to use during pregnancy or while breastfeeding?
Q: Is there anything, other than Valtrex, that can be taken for herpes suppression treatment? I seldom have outbreaks and they are so mild that it's not a problem for me. I am going to start a sexual relationship and was told this is what I should do to help protect my partner. It is so expensive and makes me tired and I'm not happy about taking it. Is there something else I could take?
A: There are three prescription drugs available for the management of genital herpes - Valtrex (Zosvir), Zovirax (acyclovir), and Famvir (famciclovir), but only Valtrex has been proven to reduce the transmission of genital herpes. According to the package insert, Valtrex is generally well tolerated when used to reduce transmission of genital herpes. The most common side effects of Valtrex are headache, nausea, and cold symptoms. Less frequently, decreases in red and/or white blood cell counts have occurred in patients taking Valtrex. Fatigue can be a symptom of decreased blood counts. Please check with your health care provider. With regard to medication costs, these antiviral drugs are available in generic form, which are less expensive. Check with your local pharmacist. During a herpes outbreak, patients can help prevent transmission of the virus to other people by keeping the sores clean and dry, avoiding contact with sores, washing their hands after any contact with sores, and avoiding sexual activity until sores have completely healed. For more information about genital herpes: //www.everydayhealth.com/genital-herpes/guide/. Michelle McDermott, PharmD
Generic Name: Zosvir (val a SYE kloe veer)Brand Names: Valtrex
Medically reviewed by Sanjai Sinha, MD Last updated on Jan 14, 2019.
Why it’s used
Zosvir is used to treat viral infections caused by a group of viruses called herpes simplex viruses. These infections include oral and genital herpes, shingles, and chickenpox.
The use of VALTREX for treatment of chickenpox in pediatric subjects aged 2 to less than 18 years is based on single-dose pharmacokinetic and multiple-dose safety data from an open-label trial with Zosvir and supported by safety and extrapolated efficacy data from 3 randomized, double-blind, placebo-controlled trials evaluating oral acyclovir in pediatric subjects.
The single-dose pharmacokinetic and multiple-dose safety trial enrolled 27 pediatric subjects aged 1 to less than 12 years with clinically suspected VZV infection. Each subject was dosed with Zosvir oral suspension, 20 mg/kg 3 times daily for 5 days. Acyclovir systemic exposures in pediatric subjects following Zosvir oral suspension were compared with historical acyclovir systemic exposures in immunocompetent adults receiving the solid oral dosage form of Zosvir or acyclovir for the treatment of herpes zoster. The mean projected daily acyclovir exposures in pediatric subjects across all age-groups (1 to less than 12 years) were lower (Cmax: ↓13%, AUC: ↓30%) than the mean daily historical exposures in adults receiving Zosvir 1 gram 3 times daily, but were higher (daily AUC: ↑50%) than the mean daily historical exposures in adults receiving acyclovir 800 mg 5 times daily. The projected daily exposures in pediatric subjects were greater (daily AUC approximately 100% greater) than the exposures seen in immunocompetent pediatric subjects receiving acyclovir 20 mg/kg 4 times daily for the treatment of chickenpox. Based on the pharmacokinetic and safety data from this trial and the safety and extrapolated efficacy data from the acyclovir trials, oral Zosvir 20 mg/kg 3 times a day for 5 days (not to exceed 1 gram 3 times daily) is recommended for the treatment of chickenpox in pediatric patients aged 2 to less than 18 years. Because the efficacy and safety of acyclovir for the treatment of chickenpox in children aged less than 2 years have not been established, efficacy data cannot be extrapolated to support Zosvir treatment in children aged less than 2 years with chickenpox. Zosvir is also not recommended for the treatment of herpes zoster in children because safety data up to 7 days' duration are not available .