acyclovir vs valganciclovir
Side-by-side comparison of acyclovir and valganciclovir Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Zovirax
Valcyte
Acyclovir is an antiviral medicine. It is used 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.
Acyclovir is used to treat shingles, which is caused by herpes zoster. It also treats genital herpes, both the first time you have it and when it comes back. Acyclovir can also treat chickenpox.
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.
Acyclovir stops the virus from growing and spreading. It does this by interfering with the virus's ability 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.
- • Malaise (feeling unwell)
- • Nausea
- • Diarrhea
- • Diarrhea
- • Fever
- • Upper respiratory infection
- • Urinary tract infection
- • Vomiting
- Tiredness 7,612
- Diarrhea 7,064
- Using the medicine for something it's not approved for 5,797
- Lung infection 5,474
- Feeling sick to your stomach 5,330
- Using the medicine for a condition it is not approved for 2,858
- CMV infection 1,756
- The medicine is not working 1,425
- Low white blood cell count 1,096
- Fever 940
Acyclovir can cause nervous system problems, especially in older adults or people with kidney problems. Tell your doctor if you have kidney problems before taking this medicine.
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. It is not known if acyclovir will harm an unborn baby. Talk to your doctor about the risks and benefits of taking acyclovir while breastfeeding.
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 acyclovir vs valganciclovir Comparison
acyclovir 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, acyclovir has 31,277 submissions while valganciclovir has 8,075. 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 substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between acyclovir and valganciclovir — always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.