Viral infections have caused millions of deaths worldwide, necessitating the need for effective antiviral medical interventions. Since 1963, 90 antiviral medications have been approved by the United States Food and Drug Administration (FDA) for treating nine viral infectious diseases.
Valacyclovir, marketed under the brand name Valtrex, was formally approved by the FDA for treating and suppressing infections caused by herpes simplex and herpes zoster viruses. Valacyclovir is often prescribed to manage genital herpes, cold sores, or shingles, helping to reduce symptoms and the frequency of outbreaks.
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What Is Valacyclovir?
Valacyclovir is an antiviral medication classified under the class of nucleoside analogs. It is a prodrug of acyclovir, meaning it converts into acyclovir in the body to exert its therapeutic effects.
Antiviral drugs can serve both treatment and preventive roles in medicine. They work by interfering with viral replication, which may help the body manage viral infections. They also help stop the spread of viruses within the body and to other individuals.
Valacyclovir stops viruses from making copies of themselves by targeting their DNA. When you take valacyclovir, your body quickly turns it into acyclovir and L-valine. Acyclovir then enters the infected cells and gets activated by a virus-specific enzyme. Once activated, it interferes with the virus's ability to build its DNA. This prevents the virus from multiplying and spreading further in your body.
Primary Uses of Valacyclovir
Doctors prescribe valacyclovir to treat infections caused by herpesviruses, specifically herpes simplex virus (HSV) and varicella-zoster virus.
Treating Herpes Simplex Virus (HSV)
HSV is a virus spread through skin-to-skin contact that causes sores and blisters on the skin and mucous membranes. There are two main types: HSV-1 and HSV-2.
HSV-1 is typically associated with oral herpes, leading to cold sores around the mouth, but it can also cause genital infections. Valacyclovir, when taken at the earliest symptoms, may help reduce the duration and severity of cold sore outbreaks.
HSV-2 primarily causes genital herpes, resulting in sores in the genital and anal areas, but can also infect the mouth. Valacyclovir reduces viral shedding, leading to fewer genital herpes recurrences, decreased transmission rates, and improved duration and severity of symptoms during outbreaks.
Treating Shingles (Herpes Zoster)
Shingles, or herpes zoster, is a viral infection caused by the reactivation of the varicella-zoster virus – the same virus that causes chickenpox. It manifests as a painful, blistering rash that typically appears on one side of the body or face.
Starting treatment within three days of the shingles rash appearing may reduce the formation of new sores by one to two days compared to no treatment.
Off-Label Uses
Valacyclovir has potential off-label applications, meaning it is prescribed for a purpose different from what the FDA has approved.
Research suggests that valacyclovir may help suppress and manage symptoms of Epstein-Barr virus (EBV), which causes infectious mononucleosis.
Researchers have also investigated valacyclovir for its potential to reduce the risk of vertical transmission of cytomegalovirus (CMV) from a pregnant mother to her unborn baby when the mother contracts CMV during pregnancy. Congenital CMV, which occurs when the infection is passed to the baby during pregnancy, can potentially cause serious health problems in the child, such as hearing loss, vision impairment, and developmental delays.
Dosage and Administration
Valacyclovir dosage is determined by the treated condition, the patient's age, and comorbid health conditions.
General Dosage Guidelines for Adults
Cold Sores
- 2 grams every 12 hours for one day
Genital Herpes
- Initial Episode: 1 gram twice daily for 10 days
- Recurrent Episodes: 500 mg twice daily for three days
- Suppressive Therapy: 500 mg to 1 gram once daily
- Transmission Reduction: 500 mg once daily
Herpes Zoster
- 1 gram three times daily for seven days
General Dosage Guidelines for Children
Cold Sores (ages 12 and older)
- 2 grams every 12 hours for one day
Chickenpox (ages two to less than 18)
- 20 mg/kg of body weight three times daily for five days; not to exceed 1 gram three times daily
Adjustments for Specific Populations
Adults with HIV who are taking valacyclovir for suppression therapy to reduce the chance of recurrent outbreaks should take 500 mg twice daily.
Dose adjustments are also recommended for patients with kidney disease. Your doctor will determine a safe valacyclovir dose based on your kidney function:
Geriatric patients with kidney impairment may need lower doses. Follow the dose adjustments outlined in the table above.
Administration Tips
Valacyclovir can be taken with or without food. To support effectiveness, it is recommended to begin taking valacyclovir at the first onset of symptoms. Take as directed by your doctor; do not take extra doses, skip doses, or stop the treatment early.
Potential Side Effects of Valacyclovir
Mild side effects can occur when taking valacyclovir. The most commonly reported side effects are:
- Headache
- Nausea
- Abdominal pain
In rare cases, more serious side effects can occur, including:
- Acute Kidney Failure: Risk factors that increase the likelihood of this occurring include older age, existing kidney problems, dehydration, and coadministration with other medications that cause kidney problems. Symptoms that may indicate acute kidney issues include decreased urination, swelling of the lower extremities, and chest discomfort.
- Brain-Related Effects: Symptoms may include agitation, confusion, and hallucinations. Older patients and those with kidney problems are at a higher risk.
- Blood Problems: In clinical trials, patients with compromised immune systems have developed thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), which are severe blood clotting conditions. Early symptoms include nausea, vomiting, bloody diarrhea, abdominal pain, and fever.
Safety Information and Precautions
Valacyclovir may not be safe for everyone. Special precautions should be taken to ensure valacyclovir is taken safely in certain populations:
- Anaphylaxis: Valacyclovir is contraindicated for patients with a history of allergy to valacyclovir or acyclovir.
- Dehydration: Kidney problems are more likely to occur when valacyclovir is given to dehydrated patients. Stay well hydrated while taking valacyclovir.
- Immunocompromise: TTP and HUS, some cases resulting in death, have been reported with doses of 8 grams daily in patients with advanced HIV and renal and allogeneic bone marrow transplant recipients.
- Pregnancy: Valacyclovir is generally considered appropriate for use during pregnancy under medical supervision. Clinical data have not identified a drug-associated risk of major birth defects with valacyclovir or its metabolite, acyclovir, in pregnant women.
- Lactation: Valacyclovir is excreted into breast milk as acyclovir. A 500 mg maternal dose of valacyclovir twice daily would provide a breastfed child with an oral acyclovir dosage of approximately 0.6 mg/kg/day. There is limited data regarding the effects of valacyclovir or acyclovir on the breastfed child or milk production.
Comparing Valacyclovir with Other Antivirals
Acyclovir and famciclovir are other antiviral medications that can treat HSV and shingles outbreaks.
Valacyclovir vs. Acyclovir
Valacyclovir has a greater bioavailability (the proportion of the drug that enters the bloodstream and is available for active use) than oral acyclovir, at approximately 54% versus 12-20%.
This means that valacyclovir may be administered less frequently than acyclovir. For example, valacyclovir is typically dosed at 1 gram three times daily for herpes zoster, compared to acyclovir, which is dosed at 800 mg five times daily.
Acyclovir is typically more affordable than valacyclovir, though prices can vary depending on location, insurance coverage, and whether a generic version is available.
Valacyclovir vs. Famciclovir
Famciclovir is a prodrug of penciclovir and has the highest bioavailability of about 77%. This means that it can be dosed less frequently than valacyclovir. For example, valacyclovir is typically dosed at 2 grams twice daily for cold sores. But you only need to take one 1500 mg dose of famciclovir.
While both antivirals are approved for treating cold sores in adults, only valacyclovir is approved for use in children ages 12 and older.
Frequently Asked Questions
1. What is valacyclovir used for?
Valacyclovir treats genital herpes, cold sores, and shingles outbreaks. It is also used for long-term suppression of recurrent herpes infections.
2. How long does it take valacyclovir to work?
Valacyclovir may begin to show effects within a few days of starting treatment. It is most effective when taken at the first onset of breakout symptoms.
3. Can I drink alcohol while taking valacyclovir?
While alcohol is not explicitly prohibited when taking valacyclovir, it can increase the risk of side effects like headache, nausea, abdominal pain, depression, and dizziness. Therefore, it's advisable to limit alcohol intake when taking this medication.
4. Is valacyclovir safe for long-term use?
Valacyclovir is generally safe for long-term use, especially for suppressing recurrent herpes infections. However, a healthcare provider should monitor long-term use to manage potential side effects and ensure kidney function remains stable.
5. Can Valacyclovir cure herpes?
Valacyclovir does not cure herpes. However, it effectively manages outbreaks, reduces symptom severity, and decreases the likelihood of transmission.
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Key Takeaways: Is Valacyclovir Right for You?
- Valacyclovir is a pharmaceutical solution for managing genital herpes, cold sores, and shingles. It relieves symptoms and reduces the frequency of outbreaks.
- Factors like bioavailability, convenient dosing, and affordability make it a preferred choice for many patients compared to other antivirals like acyclovir and famciclovir.
- Before starting valacyclovir, consult with a healthcare provider to ensure it's appropriate for your specific condition and to discuss any potential risks or interactions with other medications you may be taking.
- With the right guidance and dosing, valacyclovir may help improve the quality of life for people managing viral infections.
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