This grade answers one narrow question: how strong is the public evidence and safety record behind this drug, and how clean is its money trail and court record? It is not a verdict on whether the drug is right for you.
INDICATIONS AND USAGE Herpes Zoster Infections Acyclovir is indicated for the acute treatment of herpes zoster (shingles). Genital Herpes Acyclovir is indicated for the treatment of initial episodes and the management of recurrent episodes of genital herpes. Chickenpox Acyclovir is indicated for the treatment of chickenpox (varicella).
CONTRAINDICATIONS Acyclovir is contraindicated for patients who develop hypersensitivity to acyclovir or valacyclovir.
WARNINGS Acyclovir Tablets and Capsules are intended for oral ingestion only. Renal failure, in some cases resulting in death, has been observed with acyclovir therapy (see ADVERSE REACTIONS: Observed During Clinical Practice and OVERDOSAGE ). Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which has resulted in death, has occurred in immunocompromised patients receiving acyclovir therapy.
ADVERSE REACTIONS Herpes Simplex Short-Term Administration The most frequent adverse events reported during clinical trials of treatment of genital herpes with acyclovir 200 mg administered orally 5 times daily every 4 hours for 10 days were nausea and/or vomiting in 8 of 298 patient treatments (2.7%). Nausea and/or vomiting occurred in 2 of 287 (0.7%) patients who received placebo. Long-Term Administration The most frequent adverse events reported in a clinical trial for the prevention of recurrences with continuous administration of 400 mg (two 200 mg capsules) 2 times daily for 1 year in 586 patients treated with acyclovir were nausea (4.8%) and diarrhea (2.4%). The 589 control patients receiving intermittent treatment of recurrences with acyclovir for 1 year reported diarrhea (2.7%), nausea (2.4%), and headache (2.2%). Herpes Zoster The most frequent adverse event reported during 3 clinical trials of treatment of herpes zoster (shingles) with 800 mg of oral acyclovir 5 times daily for 7 to 10 days in 323 patients was malaise (11.5%). The 323 placebo recipients reported malaise (11.1%). Chickenpox The most frequent adverse event reported during 3 clinical trials of treatment of ...
Source: FDA SPL label for Acyclovir (Redpharm Drug), effective 20251213. Full label on DailyMed.
These are counts of reports people filed, not rates of harm. Anyone can file one, and nobody checks whether the drug was the cause. Millions of doses are taken for every report sent, so the useful part is how this drug compares with the average across all drugs.
| 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 | 2026 |
|---|---|---|---|---|---|---|---|
| 13,529 | 14,689 | 14,276 | 10,689 | 8,857 | 8,250 | 8,375 | 3,542 |
9,981 reports blaming this drug for every million Medicare prescriptions filled, which is 3.6× the typical drug on this site. (20,065 reports in 2024–2026, against 2,010,416 Medicare fills in one year. This is the one number here that accounts for how many people take the drug.)
Source: the FDA's Adverse Event Reporting System (FAERS). Reports are voluntary and unverified. Drugs that are prescribed a lot, in the news, or in lawsuits attract more reports, so the percentages are compared with the whole database to correct for that partly, not fully.
| Date | Class | Firm | Reason |
|---|---|---|---|
| 12/2022 | Class II | Eugia US LLC | Presence of Particulate Matter: Customer complaint of dark particles found inside the vial |
| 09/2022 | Class II | AuroMedics Pharma LLC | Presence of Particulate Matter: Customer complaint for a dark red, brown and black particulate floating inside vial. |
| 04/2021 | Class III | Heritage Pharmaceuticals Inc | Labeling: Incorrect or Missing Lot and/or Exp Date |
| 02/2021 | Class I | Zydus Pharmaceuticals (USA) Inc | Crystallization: customer complaints for crystallization in finished product. |
| 02/2021 | Class I | Zydus Pharmaceuticals (USA) Inc | Crystallization: customer complaints for crystallization in finished product. |
| 04/2019 | Class II | Zydus Pharmaceuticals USA Inc | Labeling; Label Mix-up; report received of one bottle labeled as Acyclovir Tablets USP 400 mg actually contained Carvedilol Tablets 6.25 mg |
| 02/2018 | Class II | Apace KY LLC | Presence of Foreign Tablet/Capsule; cartons labeled to contain Acyclovir tablets may contain Torsemide tablets in some of the blister cavities. |
| 04/2017 | Class III | Hetero USA Inc | Presence of Foreign Substance: human hair melded into tablet. |
| 07/2013 | Class II | Apotex Inc. | Presence of Particulate Matter: Product from lot KF2199, may contain tablets with pieces of nitrile rubber glove embedded within the tablets. |
Class I = reasonable probability of serious harm. Class II = temporary or reversible harm. Class III = unlikely to harm. Most generic recalls are manufacturing or labeling defects for one lot, not a verdict on the molecule.
Counts measure how much evidence exists and how transparent it is, not how big the benefit is. For that, ask your prescriber: if 100 people like me took this, how many would get better because of it, and how many would be harmed? (Doctors call these the "number needed to treat" and "number needed to harm.") It differs by condition and is the number drug ads leave out. Sources: PubMed, ClinicalTrials.gov.
In 2024, drug companies reported $0 in payments to US physicians and hospitals tied to this drug across 0 transactions.
No pending federal MDL names this drug or its brands.
Not named in any federal pharmaceutical settlement of $100M or more on record.
Sources: CMS Open Payments (Sunshine Act); Judicial Panel on Multidistrict Litigation pending docket list; DOJ settlements as tabulated on Wikipedia with links to the primary record. State-court and individual suits are not included.
| Product | Fills | $/fill |
|---|---|---|
| Acyclovir | 2,009,620 | $18 |
| Zovirax | 600 | $283 |
| Acyclovir Sodium | 196 | $179 |
1 drug in the same class grades a letter or more higher than acyclovir on this site. Worth asking whether one of them would do the same job for you.
Same ATC pharmacological class, graded ones first, best grade at the top. Being in the same class does not make them interchangeable for your condition; it makes them worth asking about.