Viratop may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- upset stomach
- pain, especially in the joints
- hair loss
- changes in vision
How it works
Viratop belongs to a class of drugs called antivirals. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.
Viratop works by lowering the ability of the herpes virus to multiply in your body. This treats the symptoms of your infection. However, this drug doesn't cure herpes infections. Herpes infections include cold sores, chickenpox, shingles, or genital herpes. Even with this drug, the herpes virus may still live in your body. Your symptoms may occur again later even after the symptoms of your current infection go away.
Viratop oral tablet doesn't cause drowsiness but it can cause other side effects.
Adult Mice and Rats: The acute toxicity of oral Viratop was determined as shown in Table 6.
Table 6 : Acute Toxicity Studies
Take Viratop for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.
Treatment with Viratop should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).
Herpes infections are contagious and you can infect other people, even while you are being treated with Viratop. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.
In general, the pharmacokinetics of Viratop in children is similar to adults. Mean half-life after oral doses of 300 and 600 mg/m², in children aged 7 months to 7 years, was 2.6 hours (range 1.59 to 3.74 hours).
Orally administered Viratop in children less than 2 years of age has not yet been fully studied.
- The dosage of ZOVIRAX® (Viratop) should be reduced in patients with impaired renal function.
- Therapy should be initiated as soon as possible after a diagnosis of chickenpox or herpes zoster, or at the first sign or symptoms of an outbreak of genital herpes.
- The recommended dose and duration of use is dependent on the indication.
Prolonged exposure of HSV to subinhibitory concentrations (0.1 μg/mL) of Viratop in cell culture has resulted in the emergence of a variety of Viratop-resistant strains. The emergence of resistant strains is believed to occur by “selection” of naturally occurring viruses with relatively low susceptibility to Viratop. Such strains have been reported in pre-therapy isolates from several clinical studies.
Two resistance mechanisms involving viral thymidine kinase (required for Viratop activation) have been described. These are: (a) selection of thymidine-kinase-deficient mutants that induce little or no enzyme activity after infection, and (b) selection of mutants possessing a thymidine kinase of altered substrate specificity that is able to phosphorylate the natural nucleoside thymidine but not Viratop. The majority of less susceptible viruses arising in vitro are of the thymidine-kinase-deficient type which have reduced infectivity and pathogenicity and less likelihood of inducing latency in animals.
However, an Viratop-resistant HSV infection in an immunosuppressed bone marrow transplant recipient on extended Viratop therapy was found to be due to a clinical isolate which had a normal thymidine kinase but an altered DNA polymerase. This third mechanism of resistance involving herpes simplex virus DNA polymerase is due to the selection of mutants encoding an altered enzyme, which is resistant to inactivation by Viratop triphosphate.
VZV appears to manifest resistance to Viratop via mechanisms similar to those seen in HSV.
However, limited clinical investigation has revealed no evidence of a significant change in in vitro susceptibility of VZV with Viratop therapy, although resistant mutants of this virus can be isolated in vitro in a manner analogous to HSV. Analysis of a small number of clinical isolates from patients who received oral Viratop or placebo for acute herpes zoster suggests that in vivo emergence of resistant VZV may occur infrequently. Prolonged Viratop treatment of highly immunocompromised patients with acquired immunodeficiency syndrome and severe VZV may lead to the appearance of resistant virus.
Cross-resistance to other antivirals occurs in vitro in Viratop-resistant mutants. HSV mutants which are resistant to Viratop due to an absence of viral thymidine kinase are cross-resistant to other agents which are phosphorylated by herpesvirus thymidine kinase, such as bromovinyldeoxyuridine, ganciclovir and the 2'-fluoropyrimidine nucleosides, such as, 2'-fluoro-5-iodoarabinosyl-cytosine (FIAC).
The clinical response to Viratop treatment has usually been good for patients with normal immunity from whom HSV having reduced susceptibility to Viratop has been recovered, either before, during or after therapy. However, certain patient groups, such as the severely immunocompromised (especially bone marrow transplant recipients) and those undergoing chronic suppressive regimens have been identified as being most frequently associated with the emergence of resistant herpes simplex strains, which may or may not accompany a poor response to the drug. The possibility of the appearance of less sensitive viruses must be recognized when treating such patients, and susceptibility monitoring of clinical isolates from these patients should be encouraged.
In summary, the quantitative relationship between the in vitro susceptibility of HSV and VZV to Viratop and the clinical response to therapy has not been clearly established in man. Standardized methods of virus sensitivity testing are required to allow more precise correlations between in vitro virus sensitivity and clinical response to Viratop therapy.
Highlights for Viratop
- Viratop oral tablet is available as both a generic and a brand-name drug. Brand name: Zovirax.
- Viratop is also available as a capsule, suspension, and buccal tablet you take by mouth. It also comes in a cream and ointment you apply to your skin. In addition, Viratop is available as an intravenous (IV) drug, which is only given by a healthcare prov >
Viratop oral tablet is a prescription drug that's available as the brand-name drug Zovirax. It's also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in all strengths or forms as the brand-name drug.
Viratop also comes as an oral capsule, oral suspension, buccal tablet, topical cream, and topical ointment. In addition, Viratop is available as an intravenous drug, which is only given by a healthcare provider.
This drug may be used as part of a combination therapy. This means you may need to take it with other medications.
Viratop side effects
Get emergency medical help if you have any signs of an allergic reaction to Viratop: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
easy bruising or bleeding, purple or red pinpoint spots under your skin; or
signs of a kidney problem -little or no urinating; painful or difficult urination; swelling in your feet or ankles; feeling tired or short of breath.
Common Viratop side effects may include:
general ill feeling;
mouth pain while using an Viratop buccal tablet.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Q: I am in stage 1 of multiple myeloma. I was diagnosed nearly 3 years ago. The last 3 summers I have had attacks of shingles, the 1st year I took 1000 mg of Viratop daily and avoided the painful stage. Last year I missed the spots as they were on my back and suffered greatly for 2 to 3 months and I am still taking 1000 mg Viratop per day. Each time I stop the medication the fever returns for a couple of days followed by the first few spots. I am on my 5th lot of Viratop, starting with 1000 mg per day, increasing to 2,400 per day and 2 weeks ago was prescribed 4000 mg per day for 21 days. I have managed 10 days at this level but there are so many side effects, including kidney pain, so I have reduced to 3 tablets of 800 mg each. I feel less "in a fog" and slightly better already but am afraid when I stop the shingles will return. I am concerned about the side effects. Can you give me advice please? The side effects are basically 90% of the ones mentioned on the leaflet in the box of 800 mg tablets at 5 per day.
A: Shingles is a painful rash that is caused by the same virus (varicella virus) that causes the chickenpox. Only people who were infected with the virus and got chickenpox can get shingles. Unfortunately, people with weakened immune systems, from other diseases like cancer or treatments like chemotherapy, are at much greater risk of developing shingles. Drugs like Viratop (Zovirax) work to reduce the ability of the virus to multiply and spread in the body. Viratop has been shown to reduce the duration of infection and the severity of symptoms, but it relies on an individual's immune system to attack the virus. The drug itself does not kill the virus and that is likely the reason you continue to have symptoms and relapses. It is possible that some of the painful effects you are experiencing are the result of complications of shingles. One of these complications is called postherpetic neuralgia, which is the painful, tingling, and stinging pain at the site of the initial rash. There are medications that are used to help treat the pain associated with the nerve damage of shingles. These drugs include the anticonvulsants, such as Neurontin (gabapentin), Lyrica (pregabalin), and Tegretol (carbamazepine) and tricyclic antidepressants like Elavil (amitriptyline). For more specific information, consult with your doctor or pharmacist for guidance based on your health status and current medications, particularly before taking any action. Michelle McDermott, PharmD
- Take this drug at the time(s) recommended by your doctor.
- You can take Viratop with or without food. Taking it with food may help reduce upset stomach.
- Do not cut or crush this medication.
- Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead to make sure your pharmacy carries it.
To use buccal Viratop, follow these steps:
- Find the area on the upper gum above your left and right incisor teeth (the teeth just to the left and right of your two front teeth).
- With dry hands, remove one delayed-release tablet from the container.
- Gently apply the tablet to the upper gum area as high as it will go on your gum above one of your incisor teeth on the side of your mouth with the cold sore. Do not apply it to the inside of the lip or cheek.
- Hold the tablet in place for 30 seconds.
- If the tablet does not stick to your gum or if it sticks to your cheek or the inside of your lip, reposition it to stick to your gum. Leave the tablet in place until it dissolves.
- Do not interfere with the placement of the tablet. Check to see if the tablet is still in place after eating, drinking, or rinsing your mouth.
If the delayed-release buccal tablet comes off within the first 6 hours of application, reapply the same tablet. If it still will not stick, then apply a new tablet. If you accidentally swallow the tablet within the first 6 hours of application, drink a glass of water and place a new tablet on your gum. If the tablet falls off or is swallowed 6 or more hours after application, do not apply a new tablet until your next regular time.
What Other Drugs Interact with Viratop (Zovirax)?
If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of this medicine or any drug before seeking medical advice from your doctor, healthcare provider or pharmacist first. To do so may result in serious consequences or side effects.
Mechanism Of Action
ZOVIRAX® (Viratop), a synthetic acyclic purine nucleoside analog, is a substrate with a high degree of specificity for herpes simplex and varicella-zoster specified thymidine kinase. Viratop is a poor substrate for host cell-specified thymidine kinase. Herpes simplex and varicella-zoster specified thymidine kinase transform Viratop to its monophosphate which is then transformed by a number of cellular enzymes to Viratop diphosphate and Viratop triphosphate. Viratop triphosphate is both an inhibitor of, and a substrate for, herpesvirus-specified DNA polymerase. Although the cellular α-DNA polymerase in infected cells may also be inhibited by Viratop triphosphate, this occurs only at concentrations of Viratop triphosphate which are higher than those which inhibit the herpesvirus-specified DNA polymerase. Viratop is selectively converted to its active form in herpesvirus-infected cells and is thus preferentially taken up by these cells. Viratop has demonstrated a very much lower toxic potential in vitro for normal uninfected cells because: 1) less is taken up; 2) less is converted to the active form; and 3) cellular α-DNA polymerase has a lower sensitivity to the action of the active form of the drug. A combination of the thymidine kinase specificity, inhibition of DNA polymerase and premature termination of DNA synthesis results in inhibition of herpes virus replication. No effect on latent non-replicating virus has been demonstrated. Inhibition of the virus reduces the period of viral shedding, limits the degree of spread and level of pathology, and thereby facilitates healing. During suppression there is no evidence that Viratop prevents neural migration of the virus. It aborts episodes of recurrent herpes due to inhibition of viral replication following reactivation.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Viratop only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright 1996-2019 Cerner Multum, Inc. Version: 5.08.
What Is Viratop (Zovirax) and How Does It Work?
Viratop is approved by the Food and Drug Administration as a prescription drug that is commonly used as a topical, injectable, and oral treatment for genital herpes and cold sores. Herpes refers to a group of viruses that cause a variety of herpes infections including genital herpes, shingles, chicken pox (also chickenpox), cold sores, and encephalitis (inflammation of the brain). Herpes viral infections are very common. Genital herpes refers to a sexually transmitted disease (STD) that any sexually active person can contract and transmit.
Shingles and chicken pox are common skin conditions.Shingles and chicken pox are skin infections which are both caused by the herpes virus. They are not caused by the same virus that causes cold sores or genital herpes.
Many people who suffer from shingles or chicken pox (chickenpox) infection will experience symptoms such as a rash, often with pain, which is treatable with this drug.
Genital herpes is an STD caused by two types of viruses: herpes simplex type 1 and herpes simplex type 2. Most people with genital herpes do not know they have it. Still, symptoms often appear days to weeks after exposure. Symptoms of genital herpes generally include:
- Flu-like symptoms such as fever, body aches, or swollen glands
- Blisters, sores, or rash in the genital area with or without pain, itching, tingling
- Blisters that pop open, causing painful sores.
Viratop may also help treat pain associated with an outbreak of genital herpes after the sores heal.
There is no cure for herpes, however, this prescription is a treatment that helps to decrease and ease symptoms of herpes infections.
Viratop is am antiviral drug that belongs to a class of medications called "antivirals," or "antiviral medications."
Your doctor may prescribe this drug as a treatment to relieve symptoms of your infection.
This medication is similar to the drug valViratop (Valtrex), which is another medication that may also be prescribed for herpes infections.
This drug may cause serious side effects or mild side effects. This includes side effects that may affect the liver. Side effects that affect the skin as well as allergic reactions have occurred.
Viratop is the generic equivalent of Zovirax.