85/100 · Critical
Manufactured by Pfizer Laboratories Div Pfizer Inc
Metronidazole Adverse Events: High Seriousness and Diverse Reactions
130,784 FDA adverse event reports analyzed
Last updated: 2026-05-12
METRONIDAZOLE is a medication tracked in the FDA Adverse Event Reporting System (FAERS), manufactured by Pfizer Laboratories Div Pfizer Inc. Based on analysis of 130,784 FDA adverse event reports, METRONIDAZOLE has a safety score of 85 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 METRONIDAZOLE include DRUG INEFFECTIVE, NAUSEA, DIARRHOEA, OFF LABEL USE, VOMITING. This page provides a comprehensive breakdown of reported side effects, safety signals, patient demographics, and AI-powered safety analysis for METRONIDAZOLE.
Metronidazole has a safety concern score of 85 out of 100, placing it in the high concern category based on analysis of FDA adverse event data. The FDA has received approximately 130,784 adverse event reports for this medication, which is primarily manufactured by Pfizer Laboratories Div Pfizer Inc.
The most commonly reported adverse events include Drug Ineffective, Nausea, Diarrhoea. Of classified reports, 83.1% were designated as serious by the FDA, meaning they involved hospitalization, disability, or other significant medical outcomes. Metronidazole reports show a high percentage of serious adverse events (83.1%).
The most common reactions include nausea, diarrhea, and abdominal pain, indicating gastrointestinal side effects. Serious reactions such as sepsis, acute kidney injury, and renal failure are also frequently reported.
Patients taking Metronidazole should monitor for the commonly reported side effects and contact their healthcare provider if they experience any unusual symptoms. Metronidazole can interact with other drugs, leading to adverse effects. Warnings include interactions with anticoagulants and anticonvulsants. This analysis is based on voluntary FDA adverse event reports and should not replace professional medical advice.
Metronidazole received a safety concern score of 85/100 (high concern). This is based on a 83.1% serious event ratio across 63,725 classified reports. The score accounts for 130,784 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: 36,061, Male: 21,642, Unknown: 211. The most frequently reported age groups are age 65 (1,041 reports), age 66 (959 reports), age 71 (959 reports). These demographics reflect reporting patterns and may not represent the full patient population.
Out of 63,725 classified reports for METRONIDAZOLE:
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.
Metronidazole can interact with other drugs, leading to adverse effects. Warnings include interactions with anticoagulants and anticonvulsants.
If you are taking Metronidazole, here are important things to know. The most commonly reported side effects include drug ineffective, nausea, diarrhoea, off label use, vomiting. While many of these may be mild and temporary, you should contact your healthcare provider if any symptoms are severe or persistent. Consult a healthcare provider before starting Metronidazole, especially if you have a history of gastrointestinal issues or allergies. Report any unusual symptoms 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 Metronidazole for safety, particularly in elderly patients and those with pre-existing conditions.
The FDA has received approximately 130,784 adverse event reports associated with Metronidazole. 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 Metronidazole include Drug Ineffective, Nausea, Diarrhoea, Off Label Use, Vomiting. By volume, the top reported reactions are: Drug Ineffective (5,469 reports), Nausea (4,694 reports), Diarrhoea (4,118 reports). These figures reflect FDA adverse event reports and may not represent the true incidence rate of these side effects in all patients taking Metronidazole.
Out of 63,725 classified reports, 52,980 (83.1%) were classified as serious and 10,745 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 Metronidazole break down by patient sex as follows: Female: 36,061, Male: 21,642, Unknown: 211. 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 Metronidazole adverse events are: age 65: 1,041 reports, age 66: 959 reports, age 71: 959 reports, age 60: 934 reports, age 69: 900 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 Metronidazole adverse event reports is Pfizer Laboratories Div Pfizer 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 Metronidazole include: Pyrexia, Drug Hypersensitivity, Pain, Abdominal Pain, Headache. 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 Metronidazole 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.
Metronidazole has a safety concern score of 85 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. Metronidazole reports show a high percentage of serious adverse events (83.1%).
Key safety signals identified in Metronidazole's adverse event data include: High percentage of serious adverse events (83.1%).. Gastrointestinal side effects are common, including nausea, diarrhea, and abdominal pain.. Reports of severe allergic reactions and drug hypersensitivity are notable.. These signals are derived from patterns in FDA reports and should be discussed with a healthcare provider for personalized assessment.
Metronidazole can interact with other drugs, leading to adverse effects. Warnings include interactions with anticoagulants and anticonvulsants. Always inform your healthcare provider about all medications, supplements, and over-the-counter drugs you are taking before starting Metronidazole.
Consult a healthcare provider before starting Metronidazole, especially if you have a history of gastrointestinal issues or allergies. Report any unusual symptoms to your healthcare provider immediately.
Metronidazole has 130,784 adverse event reports on file with the FDA. The most common reactions include nausea, diarrhea, and abdominal pain, indicating gastrointestinal side effects. The volume of reports for Metronidazole reflects both the drug's usage level and the vigilance of the reporting community.
The FDA continues to monitor Metronidazole for safety, particularly in elderly patients and those with pre-existing conditions. For the most current regulatory information, check the FDA's drug labeling database or consult your pharmacist.
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