acyclovir vs posaconazole
Side-by-side comparison of acyclovir and posaconazole Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Zovirax
Noxafil
Acyclovir is an antiviral medicine. It is used to treat infections caused by certain viruses.
Posaconazole is an antifungal medicine. It helps prevent certain fungal infections in people with weakened immune systems.
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.
Posaconazole prevents Aspergillus and Candida infections. You may need this medicine if you have a high risk of getting these infections. This often includes people who had a stem cell transplant or have certain blood cancers and are on chemotherapy.
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.
Posaconazole belongs to a class of drugs called azole antifungals. It works by stopping the growth of fungi. This helps your body fight off the infection.
- • Malaise (feeling unwell)
- • Nausea
- • Diarrhea
- • Diarrhea
- • Nausea
- • Fever
- • Vomiting
- • Headache
- 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 1,542
- The medicine is not working 1,434
- Fever with low white blood cell count 1,018
- The medicine is interacting with another medicine 930
- Death 928
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.
Posaconazole can interact with many other medicines. It can cause heart rhythm problems (QT prolongation). It can also cause liver problems. Tell your doctor about all the medicines you take.
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.
Posaconazole may harm an unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is not known if posaconazole passes into breast milk, so talk to your doctor if you are breastfeeding.
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How to Read This acyclovir vs posaconazole Comparison
acyclovir is classified in the Antiviral (Nucleoside Analog) drug class, while posaconazole sits within the Azole Antifungal class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. 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 posaconazole has 5,852. 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 posaconazole — 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.