82/100 · Critical
Manufactured by Mylan Pharmaceuticals Inc.
Valacyclovir Adverse Events: High Seriousness and Diverse Reactions
64,784 FDA adverse event reports analyzed
Last updated: 2026-05-12
VALACYCLOVIR is a medication tracked in the FDA Adverse Event Reporting System (FAERS), manufactured by Mylan Pharmaceuticals Inc.. Based on analysis of 64,784 FDA adverse event reports, VALACYCLOVIR has a safety score of 82 out of 100. This score indicates a relatively favorable safety profile, with fewer or less severe adverse events compared to many other tracked medications. The most commonly reported adverse reactions for VALACYCLOVIR include OFF LABEL USE, FATIGUE, DIARRHOEA, DRUG INEFFECTIVE, NAUSEA. This page provides a comprehensive breakdown of reported side effects, safety signals, patient demographics, and AI-powered safety analysis for VALACYCLOVIR.
Valacyclovir has a safety concern score of 82 out of 100, placing it in the high concern category based on analysis of FDA adverse event data. The FDA has received approximately 64,784 adverse event reports for this medication, which is primarily manufactured by Mylan Pharmaceuticals Inc..
The most commonly reported adverse events include Off Label Use, Fatigue, Diarrhoea. Of classified reports, 73.8% were designated as serious by the FDA, meaning they involved hospitalization, disability, or other significant medical outcomes. Valacyclovir reports show a high percentage of serious adverse events, particularly respiratory and infectious conditions.
The most common reactions include fatigue, diarrhea, and nausea, indicating gastrointestinal and general malaise effects. Serious reactions such as pneumonia, sepsis, and acute kidney injury are notable, highlighting potential severe risks. The drug is associated with a wide range of reactions, suggesting a complex safety profile. Reports indicate a significant number of drug interactions and inappropriate use issues.
Patients taking Valacyclovir should monitor for the commonly reported side effects and contact their healthcare provider if they experience any unusual symptoms. Valacyclovir is associated with various drug interactions and warnings, including potential hematological and renal effects. Healthcare providers should monitor patients for these interactions and adjust dosing accordingly. This analysis is based on voluntary FDA adverse event reports and should not replace professional medical advice.
Valacyclovir received a safety concern score of 82/100 (high concern). This is based on a 73.8% serious event ratio across 39,019 classified reports. The score accounts for 64,784 total adverse event reports and 100 distinct reaction types. This high score reflects a significant proportion of serious adverse events in the reporting data.
Adverse event reports by sex: Female: 19,605, Male: 15,435, Unknown: 66. The most frequently reported age groups are age 68 (849 reports), age 71 (843 reports), age 67 (786 reports). These demographics reflect reporting patterns and may not represent the full patient population.
Out of 39,019 classified reports for VALACYCLOVIR:
The FDA classifies an adverse event as “serious” if it results in death, hospitalization, disability, congenital anomaly, or requires intervention to prevent permanent damage.
Demographics reflect voluntary FDA adverse event reporting patterns and may not represent the full patient population.
Valacyclovir is associated with various drug interactions and warnings, including potential hematological and renal effects. Healthcare providers should monitor patients for these interactions and adjust dosing accordingly.
If you are taking Valacyclovir, here are important things to know. The most commonly reported side effects include off label use, fatigue, diarrhoea, drug ineffective, nausea. While many of these may be mild and temporary, you should contact your healthcare provider if any symptoms are severe or persistent. Follow prescribed dosing instructions carefully to avoid drug interactions and inappropriate use. Report any unusual symptoms or side effects to your healthcare provider immediately. If you experience a serious adverse reaction, seek emergency medical attention immediately or call 911. You can report side effects to the FDA's MedWatch program at 1-800-FDA-1088.
The FDA continues to monitor valacyclovir safety. Healthcare providers should report any adverse events to the FDA's MedWatch program.
The FDA has received approximately 64,784 adverse event reports associated with Valacyclovir. These reports come from healthcare professionals, consumers, and manufacturers through the FDA Adverse Event Reporting System (FAERS). Note that the number of reports does not directly indicate the frequency of side effects, as adverse events are voluntarily reported and may be underrepresented.
The most frequently reported adverse events for Valacyclovir include Off Label Use, Fatigue, Diarrhoea, Drug Ineffective, Nausea. By volume, the top reported reactions are: Off Label Use (2,544 reports), Fatigue (2,294 reports), Diarrhoea (2,120 reports). These figures reflect FDA adverse event reports and may not represent the true incidence rate of these side effects in all patients taking Valacyclovir.
Out of 39,019 classified reports, 28,794 (73.8%) were classified as serious and 10,225 as non-serious. The FDA classifies an event as "serious" if it results in death, hospitalization, disability, or other medically significant outcomes. A higher serious-event ratio warrants closer attention but does not necessarily mean the drug is unsafe.
Adverse event reports for Valacyclovir break down by patient sex as follows: Female: 19,605, Male: 15,435, Unknown: 66. This distribution reflects reporting patterns rather than actual risk differences between groups. Reporting rates can be influenced by prescribing patterns, disease demographics, and reporting behavior.
The most frequently reported age groups for Valacyclovir adverse events are: age 68: 849 reports, age 71: 843 reports, age 67: 786 reports, age 72: 759 reports, age 69: 756 reports. Age-related reporting patterns can reflect both the demographics of the patient population and potential age-related susceptibility to certain side effects.
The primary manufacturer associated with Valacyclovir adverse event reports is Mylan Pharmaceuticals Inc.. Multiple manufacturers may produce generic versions of this drug. The manufacturer listed reflects the most frequently reported brand in FDA adverse event data.
Beyond the most common reactions, other reported adverse events for Valacyclovir include: Febrile Neutropenia, Pyrexia, Pneumonia, Headache, Pain. Less common side effects can still be clinically significant. Patients should report any unusual symptoms to their healthcare provider.
You can report adverse events from Valacyclovir to the FDA through their MedWatch program at www.fda.gov/medwatch, by calling 1-800-FDA-1088, or by completing Form FDA 3500. Healthcare professionals, consumers, and manufacturers can all submit reports. Reporting helps the FDA monitor drug safety after approval.
Valacyclovir has a safety concern score of 82 out of 100 (high concern). This score is calculated from the ratio of serious to non-serious adverse events, the diversity of reported reactions, and the overall volume of reports relative to usage. Valacyclovir reports show a high percentage of serious adverse events, particularly respiratory and infectious conditions.
Key safety signals identified in Valacyclovir's adverse event data include: High percentage of serious adverse events (73.8%). Multiple reports of severe respiratory and infectious conditions. Significant number of cases involving hematological issues like neutropenia and thrombocytopenia. A wide variety of reactions, including neurological and cardiovascular effects. Reports of drug interactions and inappropriate use. These signals are derived from patterns in FDA reports and should be discussed with a healthcare provider for personalized assessment.
Valacyclovir is associated with various drug interactions and warnings, including potential hematological and renal effects. Healthcare providers should monitor patients for these interactions and adjust dosing accordingly. Always inform your healthcare provider about all medications, supplements, and over-the-counter drugs you are taking before starting Valacyclovir.
Follow prescribed dosing instructions carefully to avoid drug interactions and inappropriate use. Report any unusual symptoms or side effects to your healthcare provider immediately.
Valacyclovir has 64,784 adverse event reports on file with the FDA. The most common reactions include fatigue, diarrhea, and nausea, indicating gastrointestinal and general malaise effects. The volume of reports for Valacyclovir reflects both the drug's usage level and the vigilance of the reporting community.
The FDA continues to monitor valacyclovir safety. Healthcare providers should report any adverse events to the FDA's MedWatch program. For the most current regulatory information, check the FDA's drug labeling database or consult your pharmacist.
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