What the label lists and what reports show
Metronidazole side effects
Metronidazole's FDA label: “The most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; and abdominal cramping and constipation.” FAERS holds 63,553 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 nausea (4,691 reports).
- Generic listed
- In shortage
- Boxed warning
Check it at the source: the metronidazole FDA label on DailyMed (effective September 3, 2024, Aurobindo Pharma Limited); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of LIKMEZ?LIKMEZ may cause serious side effects including: Severe skin reactions Serious skin reactions that may affect any part of the body and can lead to death, including toxic epidermal necrolysis (TEN), Stevens-Johnson Syndrome (SJS), drug reaction with eosinophilia and systemic symptoms (DRESS), and acute generalized exanthematous pustulosis (AGEP), have happened in some people taking metronidazole (the active ingredient in LIKMEZ). These severe skin reactions may be life threatening and you may need to be treated in a hospital. […]
Source: FDA drug label (LIKMEZ), Saptalis Pharmaceuticals, LLC, effective April 18, 2025 (SPL set e20c14eb-5361-4a93-ab46-a7bd9aeb9b98), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; and abdominal cramping and constipation.
Table 2: Local Cutaneous Signs and Symptoms of Irritation That Were Worse Than Baseline in Subjects Treated with metronidazole gel for Up to 10 Weeks
This table is printed in the Metronidazole label published by Alembic Pharmaceuticals Limited of March 18, 2025; the label quoted above does not print one.
| Sign/Symptom | Metronidazole Gel, 1% (N= 544) N (%) | Vehicle (N= 184) N (%) |
|---|---|---|
| Dryness | 138 (25.4) | 63 (34.2) |
| Mild | 93 (17.1) | 41 (22.3) |
| Moderate | 42 (7.7) | 20 (10.9) |
| Severe | 3 (0.6) | 2 (1.1) |
| Scaling | 134 (24.6) | 60 (32.6) |
| Mild | 88 (16.2) | 32 (17.4) |
| Moderate | 43 (7.9) | 27 (14.7) |
| Severe | 3 (0.6) | 1 (0.5) |
| Pruritus | 86 (15.8) | 35 (19.0) |
| Mild | 53 (9.7) | 21 (11.4) |
| Moderate | 27 (5.0) | 13 (7.1) |
| Severe | 6 (1.1) | 1 (0.5) |
| Stinging/burning | 56 (10.3) | 28 (15.2) |
| Mild | 39 (7.2) | 18 (9.8) |
| Moderate | 7 (1.3) | 9 (4.9) |
| Severe | 10 (1.8) | 1 (0.5) |
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.
From the label: adverse reactions, continuedThe following reactions have been reported during treatment with metronidazole: Central Nervous System: The most serious adverse reactions reported in patients treated with metronidazole have been convulsive seizures, encephalopathy, aseptic meningitis, optic and peripheral neuropathy, the latter characterized mainly by numbness or paresthesia of an extremity. Since persistent peripheral neuropathy has been reported in some patients receiving prolonged administration of metronidazole, patients should be specifically warned about these reactions and should be told to stop the drug and report immediately to their physicians if any neurologic symptoms occur. In addition, patients have reported headache, syncope, dizziness, vertigo, incoordination, ataxia, tinnitus, hearing impairment, hearing loss, confusion, dysarthria, irritability, depression, weakness, and insomnia (see WARNINGS ). Gastrointestinal: The most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; and abdominal cramping and constipation. Mouth: A sharp, unpleasant metallic taste is not unusual. Furry tongue, glossitis, and stomatitis have occurred; these may be associated with a sudden overgrowth of Candida which may occur during therapy. …
Source: FDA drug label, Aurobindo Pharma Limited, effective September 3, 2024 (SPL set f68397ee-67db-472e-8607-4300064e37df), via openFDA; the full label on DailyMed
What do FAERS reports show?
63,553 reports list metronidazole among the medicines taken, each a report of something that happened, not proof the medicine caused it; 6,852 are coded as a death and 27,061 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, 7 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.
Reports received each year
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?
- Metronidazole: 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