6 Common Questions About Famciclovir (Famvir) Interactions
Key takeaways:
Famciclovir (Famvir) is an oral medication used to treat and prevent health conditions caused by the herpes virus. It doesn’t interact with many medications, but it can make chickenpox vaccines, Imlygic (talimogene laherparepvec), and Mavenclad (cladribine) less effective if they’re combined.
It’s generally OK to take famciclovir with antibiotics or pain medications if they’re needed. You can also combine famciclovir with topical treatments for cold sores if your prescriber recommends them.
Drinking alcohol with famciclovir can increase your risk of side effects and make it harder for your body to fight off an active herpes infection. The combination can also raise your risk of liver damage, especially if you consume large amounts of alcohol and take famciclovir long term.
Table of contents
Famciclovir (Famvir) is an antiviral medication used to treat and prevent health conditions caused by the herpes virus. In some cases, you’ll only need one dose of famciclovir. But to prevent outbreaks, you may need to take it every day.
Whether you’re taking famciclovir as a single dose or a daily medication, it’s helpful to know if it’s OK to take other medications along with it. Below, we’ll look at six common questions about famciclovir interactions to help you get the most from your medication.
1. What does famciclovir interact with?
Famciclovir doesn’t interact with many other medications. But there are a few interactions to be aware of if you’re taking it.
Chickenpox vaccines
Famciclovir can decrease the effectiveness of chickenpox vaccines (Varivax, ProQuad). This is because famciclovir is an antiviral medication that blocks the herpes virus from replicating and spreading. These vaccines contain a live herpes virus that’s been modified so it can’t cause an infection. But antivirals like famciclovir can kill off the modified live virus in the vaccine, which prevents the vaccine from working properly.
It’s recommended to stop famciclovir 24 hours before receiving one of these vaccines. And it’s best to wait 14 days after getting vaccinated to start taking famciclovir again.
Good to know: The shingles vaccine (Shingrix) isn’t a live vaccine, so it won’t interact with famciclovir. An older version of the shingles vaccine (Zostavax) was a live vaccine, but it’s been discontinued.
Imlygic
Imlygic (talimogene laherparepvec) is an immunotherapy medication that treats melanoma, a type of skin cancer. Famciclovir may reduce the effectiveness of Imlygic. Let your oncologist know if you’re taking famciclovir before you start taking Imlygic. They’ll help determine the next best steps.
Mavenclad
Lastly, famciclovir may reduce the effectiveness of Mavenclad (cladribine) if they’re taken together. Mavenclad is an oral medication that treats certain types of multiple sclerosis. Talk to your healthcare team before taking these two medications together.
2. Can you use topical herpes treatments with famciclovir?
It’s usually fine to combine an oral herpes medication, such as famciclovir, with a topical treatment option. This is because topical treatments aren’t absorbed into the bloodstream in large amounts, so there’s little risk of an issue.
Topical herpes treatments include acyclovir (Zovirax) cream and ointment, topical steroids, and docosanol (Abreva), among others. But keep in mind that topical treatments are only approved for cold sores. They’re not recommended for genital herpes or shingles. And you should get an OK from your healthcare team before trying a topical treatment with famciclovir.
3. Can you take famciclovir and valacyclovir (Valtrex) together?
No, it’s not recommended to take famciclovir and valacyclovir together. Valacyclovir (Valtrex) is another antiviral medication used for herpes infections. Like famciclovir, it can be used to treat active outbreaks and also to prevent new outbreaks.
Valacyclovir works in a very similar way to famciclovir. Combining these two medications won’t give you any benefits and may increase your risk of side effects.
4. Can you take famciclovir with antibiotics?
Taking antibiotics with famciclovir is typically OK. But remember that antibiotics don’t treat viral infections like herpes.
That being said, bacterial skin infections can happen as a complication of herpes virus infections. This often happens after scratching a herpes-related rash, which can open the skin to bacteria that cause an infection.
You shouldn’t add antibiotic treatment to famciclovir on your own. If you think you may have a bacterial infection, or your herpes rash becomes swollen, warm, or is draining pus, contact a healthcare professional. They can determine if antibiotics are needed and prescribe the best treatment for your needs.
5. Can you take famciclovir with pain medication?
Probably. Herpes infections, such as shingles and cold sores, can be painful. Over-the-counter pain relievers such as acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) are generally safe to take with famciclovir. And they can help relieve herpes-related pain.
Other common herpes pain medications include topical lidocaine cream or patches. These are also generally fine to combine with famciclovir treatment, as long as your prescriber OKs them.
Keep in mind that nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen (Aleve), aren’t appropriate for everyone. So it’s a good idea to check with your pharmacist or prescriber to make sure they’re safe for you before you take one.
6. Can you drink alcohol with famciclovir?
It depends. If you have an active herpes infection, it’s probably best to avoid alcohol. Alcohol can weaken your immune system and make it harder for your body to fight off infection.
Alcohol may also worsen some famciclovir side effects, such as headache, nausea, and diarrhea. And both alcohol and famciclovir can increase your risk of liver problems, which can go up if they’re combined. The risk is higher if you consume large amounts of alcohol and take famciclovir long term.
If you’re taking famciclovir daily to prevent a herpes outbreak, it may be fine to have an alcoholic drink now and again. But it’s best to check with your healthcare team first to make sure it’s OK based on your personal medical history.
The bottom line
Famciclovir (Famvir) is an oral medication used to treat and prevent herpes infections, including cold sores, genital herpes, and shingles. Famciclovir doesn’t interact with many medications, but it can make chickenpox vaccines, Imlygic (talimogene laherparepvec), and Mavenclad (cladribine) less effective if they’re combined. You also shouldn’t take famciclovir along with other oral herpes antivirals, such as valacyclovir (Valtrex).
It’s typically OK to take famciclovir with antibiotics or pain medications. You can also use topical medications along with famciclovir for cold sores if your prescriber recommends them. But drinking alcohol with famciclovir may increase your risk of side effects and make it harder for your body to fight off the virus.
Contact your healthcare team if you have any questions about famciclovir interactions.
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References
Amgen Inc. (2023). Imlygic- talimogene laherparepvec injection, suspension [package insert]. DailyMed.
Ayoade, F., et al. (2022). Varicella-zoster virus (chickenpox). StatPearls.
EMD Serono, Inc. (2024). Mavenclad- cladribine tablet [package insert]. DailyMed.
Kroger, A., et al. (2023). General best practice guidelines for immunization: Special situations. Centers for Disease Control and Prevention.
PD-Rx Pharmaceuticals, Inc. (2024). Famciclovir- famciclovir tablet, film coated [package insert].
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