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Norfloxacin Side Effects

Medically reviewed by Last updated on Sep 8, 2022.

Applies to norfloxacin: oral tablet.


This drug was generally well tolerated and side effects were mild. Side effects were reported in 6.5% of subjects receiving single doses and 3.6% of subjects receiving multiple doses.[Ref]


Common (1% to 10%): Nausea, abdominal cramping

Uncommon (0.1% to 1%): Abdominal pain, anal/rectal pain, constipation, diarrhea, dry mouth, dyspepsia/heartburn, flatulence, loose stools, vomiting, abdominal swelling, mouth ulcer, pruritus ani

Rare (0.01% to 0.1%): Pseudomembranous colitis, pancreatitis

Frequency not reported: Clostridioides difficile-associated diarrhea, antibiotic-associated pseudomembranous colitis

Postmarketing reports: Stomatitis


-Frequency not reported: Intestinal perforation[Ref]

The onset of pseudomembranous colitis symptoms has been reported during or after antimicrobial treatment.

Pseudomembranous colitis and pancreatitis have also been reported during postmarketing experience.[Ref]

Nervous system

Cases of sensory or sensorimotor axonal polyneuropathy (affecting small and/or large axons) resulting in paresthesias, hypoesthesias, dysesthesias, and weakness have been reported.

Seizures reported in association with this drug have occurred, generally in older patients. A patient with myasthenia gravis had her condition deteriorate during 2 different courses of this drug.

Paresthesia, polyneuropathy (including Guillain-Barre syndrome), tinnitus, and exacerbation of myasthenia gravis have also been reported during postmarketing experience.[Ref]

Common (1% to 10%): Headache, dizziness

Uncommon (0.1% to 1%): Tingling of the fingers, somnolence/drowsiness, bitter taste

Rare (less than 0.1%): Peripheral sensory neuropathy/sensory axonal polyneuropathy, peripheral sensory motor neuropathy/sensorimotor axonal polyneuropathy, paresthesia, polyneuropathy, Guillain-Barre syndrome, seizures, tinnitus, exacerbation of myasthenia gravis

Frequency not reported: Dysesthesia, altered taste

Postmarketing reports: Generalized seizures, convulsions, myoclonus, tremors, peripheral neuropathy (may be irreversible), ataxia, hypoesthesia, hearing loss, dysgeusia, hypertonia, dysarthria, dysphasia


-Postmarketing reports: Dysphasia[Ref]


Uncommon (0.1% to 1%): Allergies/allergic reactions

Rare (0.01% to 0.1%): Anaphylactic/anaphylactoid reactions

Postmarketing reports: Hypersensitivity reactions (including anaphylactoid reactions, anaphylaxis, angioedema, dyspnea, vasculitis, urticaria, arthritis, arthralgia, myalgia, interstitial nephritis, DRESS syndrome)[Ref]


Interstitial nephritis has also been reported during postmarketing experience.[Ref]

Rare (0.01% to 0.1%): Interstitial nephritis

Frequency not reported: Decreased renal function, nephrotic syndrome (which has occurred in patients treated with high doses), increased BUN/serum urea, increased serum creatinine

Postmarketing reports: Renal failure


-Frequency not reported: Renal calculi[Ref]


Common (1% to 10%): Elevated ALT, elevated AST, cholestatic hepatitis, hepatitis

Frequency not reported: Eosinophilic necrotizing granulomatous hepatitis

Postmarketing reports: Jaundice (including cholestatic jaundice), elevated liver function tests, hepatic failure (including fatal cases)


-Frequency not reported: Hepatic necrosis[Ref]

Hepatitis has also been reported during postmarketing experience.[Ref]


Common (1% to 10%): Eosinophilia, decreased WBC, decreased neutrophil count, decreased platelet count

Uncommon (0.1% to 1%): Decreased hematocrit, decreased hemoglobin, increased eosinophils, leukopenia, neutropenia, thrombocytopenia, prothrombin time prolongation

Rare (0.01% to 0.1%): Hemolytic anemia

Postmarketing reports: Agranulocytosis


-Postmarketing reports: Agranulocytosis, prothrombin time prolongation[Ref]

Eosinophilia was reported in 7.5% of 1 study population. Leukopenia and neutropenia have been reported in up to 1% of patients. Hemolytic anemia has sometimes been associated with glucose-6-phosphate dehydrogenase deficiency.

Leukopenia, neutropenia, hemolytic anemia, prothrombin time prolongation, and thrombocytopenia have also been reported during postmarketing experience.[Ref]


Quinolones, including this drug, have been associated with ruptures of the shoulder, hand, Achilles, and other tendons resulting in disability or requiring surgical repair. Elderly patients and patients concomitantly using corticosteroids may be at increased risk.

Renal transplant patients have an increased risk of Achilles tendinitis and rupture over the general population. Quinolone use has been shown to increase that risk further in this population (12% in quinolone-treated patients versus 7% in patients not treated).

There have been 23 reports of tendinitis submitted to the Australian Adverse Drug Reactions Committee (ADRAC) between 2006 and 2008, including reports of Achilles tendonitis, tendon rupture, and tendon pain and swelling. The reports were primarily in male patients (15 cases) older than 56 years who used ciprofloxacin for 2 to 14 days. In 19 of the reported cases, a fluoroquinolone (generally ciprofloxacin) was the primary suspect; however, details of concomitant serious medical conditions were not documented in most of the reports.

Tendinitis and tendon rupture have also been reported during postmarketing experience.[Ref]

Common (1% to 10%): Rhabdomyolysis

Uncommon (0.1% to 1%): Bursitis, back pain

Rare (0.01% to 0.1%): Tendinitis, tendosynovitis, myalgia/muscle pains, joint pains, joint inflammation

Very rare (less than 0.01%): Tendon rupture (e.g., Achilles tendon)

Frequency not reported: Bilateral arthritis of the ankles

Postmarketing reports: Elevated creatine kinase, muscle spasms[Ref]


Common (1% to 10%): Asthenia, elevated alkaline phosphatase

Uncommon (0.1% to 1%): Fever, fatigue, chest pain, foot or hand swelling, chills, edema

Rare (0.01% to 0.1%): Tiredness

Frequency not reported: Weakness, elevated LDH


-Postmarketing reports: Elevated serum triglycerides, elevated serum cholesterol, elevated serum potassium[Ref]


Uncommon (0.1% to 1%): Rash, pruritus, hyperhidrosis, erythema, urticaria

Rare (0.01% to 0.1%): Petechiae, hemorrhagic bullae/papules with vasculitis, skin reactions, exfoliative dermatitis, toxic epidermal necrolysis (Lyell's syndrome), erythema multiforme, Stevens-Johnson syndrome, photosensitivity, angioedema

Frequency not reported: Systemic contact dermatitis

Postmarketing reports: Leukocytoclastic vasculitis, drug rash with eosinophilia and systemic symptoms (DRESS syndrome), photosensitivity/phototoxicity reactions, periorbital erythema


-Frequency not reported: Erythema nodosum, photosensitivity (phototoxic reactions, photosensitization with vesiculation, redness, swelling, discoloration)[Ref]

Rash, toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema multiforme, pruritus, and exfoliative dermatitis have also been reported during postmarketing experience. Rash has been reported as the most common side effect during postmarketing experience.

A 70-year-old male developed systemic contact dermatitis, an itchy papulopustular eruption from the thighs to the abdomen, after 3 days of therapy with this drug. The patient was treated with prednisone for 15 days. A patch test 1 month later resulted in a reaction to quinolone mix.

Photosensitivity has been reported in patients extensively exposed to sunlight or sunbeds during ongoing therapy with quinolone-like agents.[Ref]


Crystalluria has occurred in patients taking doses greater than 1200 mg/day and whose urine pH was 7 to 7.8.

Crystalluria and vaginal candidiasis have also been reported during postmarketing experience.[Ref]

Common (1% to 10%): Increased urine protein

Uncommon (0.1% to 1%): Dysmenorrhea, renal colic, crystalluria

Rare (0.01% to 0.1%): Vaginal candidiasis

Frequency not reported: Glycosuria, vaginal swelling

Postmarketing reports: Proteinuria


-Postmarketing reports: Crystalluria, albuminuria, candiduria, cylindruria, hematuria, vaginal candidiasis[Ref]


Uncommon (0.1% to 1%): Myocardial infarction, palpitation

Frequency not reported: Tachycardia, ECG QT prolonged, cardiovascular collapse

Postmarketing reports: Prolonged QTc interval, ventricular arrhythmia (including torsade de pointes)


-Postmarketing reports: Postural hypotension[Ref]


Uncommon (0.1% to 1%): Blurred vision

Rare (0.01% to 0.1%): Visual disturbance, increased lacrimation

Postmarketing reports: Diplopia, uveitis, nystagmus, conjunctivitis, eye pain/irritation, hemophthalmia


-Postmarketing reports: Nystagmus, visual disturbances[Ref]

Visual disturbances have also been reported during postmarketing experience.[Ref]


Uncommon (0.1% to 1%): Anorexia

Rare (0.01% to 0.1%): Loss of appetite

Postmarketing reports: Dysglycemia


-Frequency not reported: Acidosis

-Postmarketing reports: Symptomatic hypoglycemia, elevated blood glucose[Ref]



-Frequency not reported: Hiccough[Ref]


Uncommon (0.1% to 1%): Anxiety, depression, insomnia, sleep disturbances

Rare (0.01% to 0.1%): Mood changes, nervousness, irritability, euphoria, disorientation, hallucinations, confusion, psychic disturbances, psychotic reactions


-Frequency not reported: Manic reactions[Ref]

Psychic disturbances (including psychotic reactions) and confusion have also been reported during postmarketing experience.[Ref]


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Further 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.