What the label lists and what reports show
Penciclovir side effects
Penciclovir's FDA label lists its adverse reactions in its own words. FAERS holds 359 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is headache (31 reports).
- Generic listed
Check it at the source: the penciclovir FDA label on DailyMed (effective September 4, 2019, Mylan Pharmaceuticals Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsOne or more local skin reactions were reported by 3% of the subjects treated with penciclovir cream and 4% of placebo-treated patients. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Mylan at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Studies Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. In two double-blind, placebo-controlled trials, 1,516 patients were treated with penciclovir cream and 1,541 with placebo. One or more local adverse reactions were reported by 3% of the patients treated with penciclovir cream and 4% of placebo-treated patients. …
TABLE 1 - Local Adverse Reactions Reported in Phase III Trials
| Reaction | Penciclovir N = 1,516 % | Placebo N = 1,541 % |
|---|---|---|
| Application site reaction | 1 | 2 |
| Hypesthesia/Local anesthesia | < 1 | < 1 |
| Taste perversion | < 1 | < 1 |
| Rash (erythematous) | < 1 | < 1 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
Source: FDA drug label, Mylan Pharmaceuticals Inc., effective September 4, 2019 (SPL set 9cb88c28-d9c9-45e3-b4fe-083327f122de), via openFDA; the full label on DailyMed
What do FAERS reports show?
359 reports list penciclovir among the medicines taken, each a report of something that happened, not proof the medicine caused it; 24 are coded as a death and 92 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 2 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Penciclovir: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions