What to Avoid While on Valtrex? Key Precautions for Safe Treatment

October 11, 2025 •

5 min read

Valtrex (valacyclovir) is a commonly prescribed antiviral drug used to treat various herpes infections, including cold sores, genital herpes, and shingles. Knowing what to avoid while on Valtrex is essential for preventing complications, minimizing side effects, and ensuring the medication's effectiveness.

Quick Summary

This guide provides critical information on precautions to take when using Valtrex. It details drug and alcohol interactions, risks for those with underlying health conditions, and lifestyle adjustments necessary for safe and successful antiviral therapy.

Key Points

Avoid Nephrotoxic Drugs: Steer clear of medications known to harm the kidneys, such as NSAIDs (ibuprofen, naproxen), as they can increase the risk of kidney damage when combined with Valtrex.
Limit or Avoid Alcohol: Combining alcohol with Valtrex can worsen side effects like dizziness and nausea and place added strain on your liver and kidneys. Excessive drinking should be avoided.
Stay Hydrated: Drinking plenty of water is essential while taking Valtrex to help your kidneys process the medication efficiently and prevent potential kidney problems.
Exercise Caution with Vaccines: Inform your doctor of any upcoming vaccinations, particularly live vaccines like those for chickenpox or shingles, as Valtrex can reduce their effectiveness.
Be Mindful of Underlying Conditions: Those with kidney disease, weakened immune systems (e.g., HIV/AIDS), or a history of organ transplants should exercise extra caution due to an increased risk of severe side effects.
Do Not Spread the Virus: Remember that Valtrex does not prevent the spread of herpes. Continue to take precautions, such as avoiding sexual contact during an outbreak and practicing good hygiene.

Understanding Valtrex and Its Precautions

Valtrex, the brand name for valacyclovir, works by slowing the growth and spread of the herpes virus in the body. While it is a highly effective treatment, its metabolism and potential side effects require users to be mindful of certain interactions. The drug is primarily processed and excreted by the kidneys, which makes renal function a key consideration for safe use. The following sections outline the most important things to avoid while on Valtrex.

Medications That Interact with Valtrex

Mixing Valtrex with other drugs can be dangerous, particularly those that also affect the kidneys, as this can increase the risk of kidney damage. Always provide your healthcare provider with a complete list of all medications, supplements, and over-the-counter drugs you are taking.

Kidney-Damaging Medications (Nephrotoxic Agents)

Combining Valtrex with other nephrotoxic agents significantly increases the strain on your kidneys. This can lead to reduced kidney function or, in rare cases, acute kidney injury. Examples of such drugs include:

Non-steroidal anti-inflammatory drugs (NSAIDs): These include common pain relievers like ibuprofen (Advil, Motrin) and naproxen (Aleve).
Certain antibiotics: Specific antibiotics, including aminoglycosides like gentamicin and tobramycin, can be hard on the kidneys.
Immunosuppressants: Drugs such as cyclosporine and tacrolimus, often used after organ transplants, can increase the risk of kidney damage when combined with Valtrex.
Chemotherapy drugs: Some chemotherapy medications, like methotrexate, are known to be nephrotoxic.

Other Important Drug Interactions

Acyclovir: Valtrex is a prodrug of acyclovir, meaning it converts into acyclovir in the body. Taking both medications at the same time is not recommended and can lead to overdose and increased side effects.
Foscarnet: This antiviral drug, when taken with Valtrex, can increase the risk of kidney damage.
Cimetidine and Probenecid: These medications can cause elevated levels of valacyclovir in the body, which can increase the risk of side effects.
Live vaccines: Valtrex can reduce the effectiveness of live vaccines, such as the varicella (chickenpox) or zoster (shingles) vaccines. Your doctor may advise a waiting period after taking Valtrex before receiving these vaccines.

Potential Risks of Alcohol Consumption with Valtrex

While no explicit drug interaction between Valtrex and alcohol is typically noted on medication labels, health experts advise caution. The potential risks largely stem from the fact that both are processed by the liver and can intensify side effects.

Risks of mixing alcohol and Valtrex include:

Exacerbated side effects: Both alcohol and Valtrex can cause dizziness, headaches, nausea, and drowsiness. Combining them can intensify these symptoms, making activities like driving or operating machinery unsafe.
Increased liver and kidney strain: The liver and kidneys work to metabolize both substances. Excessive alcohol consumption puts extra stress on these organs, increasing the risk of damage, especially for individuals with pre-existing conditions.
Weakened immune system: Heavy drinking can suppress the immune system, which is counterproductive when taking an antiviral medication designed to help your body fight infection.

Underlying Medical Conditions

Certain pre-existing health conditions can significantly increase the risk of severe adverse reactions while on Valtrex. It is imperative to inform your doctor if you have any of the following:

Kidney Disease: As mentioned, Valtrex is excreted by the kidneys. Impaired kidney function can lead to a dangerous buildup of the drug in the system. Dosage adjustments are often necessary for patients with chronic kidney disease or those on dialysis.
Weakened Immune System: People with compromised immunity, such as those with HIV/AIDS or who have undergone a bone marrow or kidney transplant, may have an increased risk of developing a serious blood disorder called thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS).
Older Age: The elderly population is more susceptible to some of the side effects, particularly mental and mood changes and kidney problems.

Lifestyle Adjustments and Other Avoidances

Dehydration: Dehydration increases the risk of kidney complications while on Valtrex. It is crucial to drink plenty of water and stay well-hydrated throughout your treatment.
Operating Machinery: If you experience side effects like dizziness or confusion, you should avoid driving or operating heavy machinery until you know how the medication affects you.
Spreading the Infection: Taking Valtrex does not prevent the spread of herpes viruses. You must still practice precautions to avoid infecting others. This includes:
- Avoiding sexual contact during a genital herpes outbreak and using condoms between outbreaks.
- Avoiding close physical contact, such as kissing, during a cold sore outbreak.
- Washing your hands frequently after touching an infected area.
Herbal Supplements: The safety and effectiveness of combining Valtrex with various herbal supplements, such as St. John's Wort, is not well-researched. It is best to consult a doctor before taking any supplements to avoid potential unknown interactions.

Valtrex Interactions at a Glance


Interaction Type	Examples	Potential Risk	Precautions
Other Medications	NSAIDs (ibuprofen, naproxen), certain antibiotics (gentamicin), immunosuppressants (cyclosporine), Foscarnet, Probenecid, Cimetidine	Increased risk of kidney damage, elevated drug levels, potential overdose if combined with acyclovir	Always inform your doctor of all medications you are taking, including OTC drugs and supplements.
Alcohol	Beer, wine, liquor	Intensified side effects (dizziness, nausea), increased strain on kidneys and liver, weakened immune system	Limit or avoid alcohol during treatment. Consult your healthcare provider, especially with underlying health conditions.
Live Vaccines	Varicella, Zoster	Reduced effectiveness of the vaccine	Inform your doctor of recent or upcoming vaccinations. You may need to wait 24 hours before and 14 days after receiving the vaccine.
Dehydration	Not drinking enough water	Increased risk of kidney problems, especially at higher doses or with long-term use	Drink plenty of water throughout the day to support kidney function.
Underlying Conditions	Kidney disease, HIV/AIDS, history of organ transplant	Higher risk of serious side effects like kidney failure or blood disorders (TTP/HUS)	Discuss your full medical history with your doctor for proper dosage and monitoring.

Conclusion

While Valtrex is a vital medication for managing herpes virus infections, its safe use depends on understanding and avoiding key interactions. Patients should prioritize their health by carefully considering alcohol consumption, disclosing all other medications and supplements to their doctor, and being mindful of underlying health issues like kidney problems. Staying well-hydrated is a simple but important step in protecting kidney function. By following these precautions, patients can maximize the therapeutic benefits of Valtrex while minimizing the risk of adverse effects. Always consult with a healthcare professional for personalized advice tailored to your specific health needs.

For more detailed information, please refer to authoritative medical sources, such as the prescribing information available on Drugs.com, for specific warnings and contraindications related to valacyclovir.

Frequently Asked Questions

It is generally advised to limit or avoid alcohol while on Valtrex. Both substances are processed by the liver and can intensify side effects like dizziness and nausea, and excessive drinking puts added strain on the liver and kidneys.

You should generally avoid NSAIDs like ibuprofen (Advil) and naproxen (Aleve) while on Valtrex, as they can increase the risk of kidney problems. Acetaminophen (Tylenol) is often considered a safer alternative, but you should always consult your doctor.

If you have pre-existing kidney disease or are on dialysis, you must inform your doctor. Valtrex is processed by the kidneys, and impaired function can lead to drug accumulation and severe complications. Your doctor will likely need to adjust your dosage.

The interactions between Valtrex and many supplements are not well-researched. For this reason, it is best to tell your doctor or pharmacist about any supplements or herbal remedies you are taking, as some, like St. John's Wort, could affect metabolism.

Valtrex can interfere with the effectiveness of live vaccines, such as those for varicella (chickenpox) and zoster (shingles). You should inform your healthcare provider of your medication use to determine the best timing for your vaccination schedule.

Yes, taking Valtrex does not prevent the spread of herpes viruses. You must continue to practice safe sex, use barrier protection like condoms, and avoid contact with infected lesions to prevent transmission to others.

If you experience common side effects such as dizziness, headache, or confusion, you should avoid driving or operating heavy machinery until you are certain how the medication affects you.