famciclovir vs valganciclovir
PlainMeds reviewed this comparison against our methodology in August 2026. It places FDA and CMS record fields side by side, without recommending either medication.
Side-by-side comparison of famciclovir and valganciclovir. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Famvir
Valcyte
Famciclovir is an antiviral medicine. It helps to treat infections caused by certain viruses.
Valganciclovir is an antiviral medicine. It helps prevent cytomegalovirus (CMV) disease in children who have received kidney or heart transplants.
This medicine treats herpes infections. It can treat cold sores, genital herpes, and shingles. It can also prevent genital herpes outbreaks. This medicine may not work for everyone, including first-time genital herpes, eye shingles, or certain immunocompromised patients.
This medicine prevents CMV disease in children after they get a kidney or heart transplant. CMV is a virus that can cause problems in people with weakened immune systems. Valganciclovir helps to stop the virus from growing and causing illness.
Famciclovir stops the virus from multiplying. It does this by blocking a key enzyme the virus needs to make copies of itself. This helps your body fight off the infection.
Valganciclovir changes into ganciclovir in your body. Ganciclovir stops CMV from making copies of itself. This helps to prevent or treat CMV infections.
- • Headache
- • Nausea
- • Diarrhea
- • Fever
- • Upper respiratory infection
- • Urinary tract infection
- • Vomiting
- Fatigue 185
- Diarrhoea 179
- Nausea 145
- Headache 135
- Pain 118
- Cytomegalovirus Infection 1,756
- Neutropenia 1,096
- Pyrexia 939
- Diarrhoea 916
- Leukopenia 914
If you have kidney problems, make sure your doctor knows. Taking too much famciclovir when you have kidney problems can damage your kidneys.
Valganciclovir can cause serious side effects, including: - Lowered blood cell counts. This can lead to infections and bleeding. - Fertility problems in both men and women. - Birth defects if taken during pregnancy. - Cancer. Talk to your doctor about these risks.
Tell your doctor if you are pregnant or plan to become pregnant. Untreated herpes during pregnancy can harm the baby. It is not known if famciclovir passes into breast milk.
This medicine can cause birth defects. Do not take it if you are pregnant or plan to become pregnant. Breastfeeding is not recommended while taking this medicine.
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How to Read This famciclovir vs valganciclovir Comparison
famciclovir is classified in the Antiviral (Nucleoside Analog) drug class, while valganciclovir sits within the Antiviral (Nucleoside Analog) class. Because both drugs share the same classification, they are often considered interchangeable in theory, but clinical outcomes rarely track that cleanly. Both drugs are prescription-only, so a licensed provider must authorize use.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, famciclovir has 762 submissions while valganciclovir has 5,621. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. No direct interaction between these two drugs is listed in our FDA-derived dataset, though co-prescription still warrants pharmacist review. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot represent individual circumstances. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This registry does not provide medical, treatment, substitution, or medication-change directions for famciclovir or valganciclovir.
Registry boundary: This comparison displays source-record fields and does not provide individualized medical direction.