Flagyl 375 Side Effects
Generic name: metronidazole
Medically reviewed by Drugs.com. Last updated on Jul 5, 2023.
Note: This document contains side effect information about metronidazole. Some dosage forms listed on this page may not apply to the brand name Flagyl 375.
Applies to metronidazole: oral capsule, oral powder for suspension, oral tablet. Other dosage forms:
Oral route (Tablet; Tablet, Extended Release)
Metronidazole has been shown to be carcinogenic in mice and rats. Unnecessary use of the drug should be avoided. Its use should be reserved only for conditions for which it is approved.
Serious side effects of Flagyl 375
Along with its needed effects, metronidazole (the active ingredient contained in Flagyl 375) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking metronidazole:
- back pain
- blurred vision
- burning, numbness, tingling, or painful sensations in the hands or feet
- changes in speech patterns
- decreased vision
- eye pain
- lack of coordination
- seeing or hearing things that are not there
- shakiness and unsteady walk
- slurred speech
- stiff neck or back
- trouble speaking
- unsteadiness, trembling, or other problems with muscle control or coordination
- unusual tiredness or weakness
- weakness in the arms, hands, legs, or feet
- Black, tarry stools
- blood in the urine
- body aches or pain
- burning while urinating
- clumsiness or unsteadiness
- difficulty with breathing
- ear congestion
- feeling of pelvic pressure
- frequent or painful urination
- irregular heartbeat
- loss of voice
- nasal congestion
- pinpoint red spots on the skin
- runny nose
- skin rash, hives, redness, itching
- stomach and back pain (severe)
- unusual bleeding or bruising
- vaginal irritation, discharge, or dryness not present before taking the medicine
- Bleeding gums
- chest pain
- dark urine
- fast heartbeat
- loss of appetite
- painful or difficult urination
- pains in the stomach, side, or abdomen, possibly radiating to the back
- sore throat
- sores, ulcers, or white spots on the lips or in the mouth
- swollen glands
- yellow eyes or skin
Incidence not known
- Blistering, peeling, or loosening of the skin
- bloody or cloudy urine
- burning while urinating
- continuing diarrhea
- continuing stomach pain
- feeling of warmth
- increased volume of pale, dilute urine
- joint or muscle pain
- loss of bladder control
- red skin lesions, often with a purple center
- red, irritated eyes
- redness of the face, neck, arms, and occasionally, upper chest
- redness of the skin
Other side effects of Flagyl 375
Some side effects of metronidazole may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Dizziness or lightheadedness
- feeling of constant movement of self or surroundings
- sensation of spinning
- stomach cramps
- trouble sleeping
- weight loss
- Change in taste sensation
- dry mouth
- pain or tenderness around the eyes and cheekbones
- tender, swollen glands in the neck
- trouble with swallowing
- unpleasant or sharp metallic taste
- voice changes
Incidence not known
- Decreased interest in sexual intercourse
- inability to have or keep an erection
- loss in sexual ability, desire, drive, or performance
- painful sexual intercourse
For Healthcare Professionals
Applies to metronidazole: compounding powder, intravenous powder for injection, intravenous solution, oral capsule, oral suspension, oral tablet, oral tablet extended release.
The most serious side effects reported were convulsive seizures, encephalopathy, aseptic meningitis, optic neuropathy, and peripheral neuropathy (characterized by numbness/paresthesia of an extremity).[Ref]
Very common (10% or more): Headache (up to 18%)
Common (1% to 10%): Dysgeusia/taste perversion (e.g., metallic taste, sharp unpleasant metallic taste, taste of alcoholic beverages modified), dizziness
Rare (0.01% to 0.1%): Encephalopathy (e.g., confusion, fever, headache, hallucinations, paralysis, light sensitivity, disturbances in sight and movement, stiff neck), aseptic meningitis, seizure, somnolence, peripheral neuropathy, ataxia
Very rare (less than 0.01%): Subacute cerebellar syndrome (e.g., ataxia, dysarthria, gait impaired, nystagmus, tremor), drowsiness, convulsions, incoordination
Frequency not reported: Dysarthria, hypoesthesia, paresthesia, peripheral sensory neuropathy, transient epileptiform seizures, hearing impaired/hearing loss (including sensorineural), tinnitus, taste disorders/unpleasant taste in mouth, nystagmus, convulsive seizure, numbness, syncope, vertigo, paralysis[Ref]
Very common (10% or more): Nausea (up to 10%)
Common (1% to 10%): Abdominal pain, diarrhea, dry mouth, stomatitis, glossitis
Rare (0.01% to 0.1%): Pancreatitis, upper abdominal pain/epigastralgia, vomiting
Frequency not reported: Constipation, tongue discoloration, oral mucositis, furry/furred tongue, gastrointestinal disturbances (e.g., epigastric pain/distress), proctitis, sudden overgrowth of Candida in mouth, abdominal cramping, dyspepsia, pseudomembranous colitis, mucositis[Ref]
Very common (10% or more): Vaginitis (up to 15%)
Rare (0.01% to 0.1%): Chromaturia
Very rare (less than 0.01%): Darkened urine
Common (1% to 10%): Bacterial infection, influenza-like symptoms
Uncommon (0.1% to 1%): Asthenia
Rare (0.01% to 0.1%): Mucosal inflammation, pyrexia/fever
Very rare (less than 0.01%): Flushing
Common (1% to 10%): Myalgia
Very rare (less than 0.01%): Arthralgia
Uncommon (0.1% to 1%): Leukopenia
Frequency not reported: Eosinophilia, bone marrow aplasia, bone marrow depression, blood dyscrasia[Ref]
Very rare (less than 0.01%): Skin rash, pustular eruptions, acute generalized exanthematous pustulosis, pruritus
Frequency not reported: Fixed drug eruption, swelling face, urticaria, hyperhidrosis, erythema, drug reaction with eosinophilia and systemic symptoms (DRESS), erythematosus rash, mild erythematous eruptions, pustulosis[Ref]
Rare (0.01% to 0.1%): Cholestatic hepatitis
Very rare (less than 0.01%): Increased liver enzymes (AST, ALT, alkaline phosphatase), cholestatic/mixed hepatitis, hepatocellular liver injury, jaundice, liver failure requiring liver transplant, abnormal liver function tests
Frequency not reported: Increased liver enzyme, hepatotoxicity/liver failure in patients with Cockayne syndrome, drug-induced hepatitis[Ref]
Frequency not reported: Serum sickness-like reaction, immediate/delayed hypersensitivity reactions, anaphylactic reaction, hypersensitivity
Rare (0.01% to 0.1%): Hallucinations
Very rare (less than 0.01%): Confusion/confusional state, psychotic disorders
Rare (0.01% to 0.1%): Optic neuropathy, diplopia, myopia
Very rare (less than 0.01%): Vision disorders (e.g., diplopia, myopia)
Frequency not reported: Optic neuropathy/neuritis, saccadic eye movement, blurred vision, decreased visual acuity, changed color vision, light sensitivity[Ref]
An increased incidence of gastrointestinal and certain extraintestinal cancers have been reported in patients with Crohn's disease. Breast and colon cancer have been reported in medical literature in Crohn's disease patient treated with high doses of this drug for a prolonged duration; causality was not established.[Ref]
Frequency not reported: Injection site reaction, thrombophlebitis[Ref]
Frequently asked questions
- What happens if you drink alcohol with metronidazole?
- What are the most common skin conditions? (with photos)
- How long does it take for metronidazole to work?
- Can metronidazole cause a yeast infection?
- What can I do about the metallic taste of Flagyl?
- Does Flagyl cause diarrhea?
- Does metronidazole treat chlamydia?
- Can you have sex while taking metronidazole?
- How long does it take metronidazole to leave your system?
More about Flagyl 375 (metronidazole)
- Check interactions
- Compare alternatives
- Drug images
- Dosage information
- During pregnancy
- Drug class: amebicides
Related treatment guides
1. Product Information. Flagyl (metronidazole). Searle. 2002.
2. Cerner Multum, Inc. UK Summary of Product Characteristics.
3. Cerner Multum, Inc. Australian Product Information.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Some side effects may not be reported. You may report them to the FDA.