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Norfloxacin Side Effects

For the Consumer

Applies to norfloxacin: oral tablet

As well as its needed effects, norfloxacin may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking norfloxacin, check with your doctor immediately:

  • Chest pain or discomfort
  • chills
  • diarrhea
  • discouragement
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling sad or empty
  • fever
  • flushing or redness of the skin
  • hives or welts
  • increased sweating
  • irritability
  • irritation or soreness of the mouth
  • itching of the rectal area
  • itching skin
  • lack of appetite
  • loss of interest or pleasure
  • nausea
  • pain and inflammation at the joints
  • pain or discomfort in the arms, jaw, back, or neck
  • redness of the skin
  • shortness of breath
  • skin rash
  • sweating
  • swelling of the foot or hand
  • swelling of the stomach
  • tingling of the fingers
  • tiredness
  • trouble with concentrating
  • trouble with sleeping
  • unusually warm skin
  • vomiting
Incidence not known:
  • Abdominal or stomach cramps or tenderness
  • anxiety
  • back, leg, or stomach pains
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • bloating
  • blood in the urine or stools
  • blurred vision
  • bone pain
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • clay-colored stools
  • cold sweats
  • constipation
  • cool, pale skin
  • cough or hoarseness
  • cracks in the skin
  • dark-colored urine
  • decreased frequency or amount of urine
  • diarrhea, watery and severe, which may also be bloody
  • difficulty with breathing, chewing, swallowing, or talking
  • difficulty with moving
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • double vision
  • drooping eyelids
  • dry mouth
  • dry skin
  • false sense of well-being
  • fever with or without chills
  • fruit-like breath odor
  • general body swelling
  • general feeling of tiredness or weakness
  • greatly decreased frequency of urination or amount of urine
  • headache
  • inability to move the arms and legs
  • increased blood pressure
  • increased hunger
  • increased sensitivity of the skin to sunlight
  • increased thirst
  • increased urination
  • indigestion
  • irregular or slow heart rate
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • loss of heat from the body
  • lower back or side pain
  • mood or mental changes
  • mood swings
  • muscle aching or cramping
  • muscle pain or stiffness
  • muscle weakness
  • nervousness
  • nightmares
  • nosebleeds
  • numbness or tingling in the hands, feet, or lips
  • pain or burning while urinating
  • pain, inflammation, or swelling in the calves, shoulders, or hands
  • pain, swelling, or redness in the joints
  • painful or difficult urination
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • personality changes
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • red, swollen skin
  • scaly skin
  • seizures
  • severe sunburn
  • severe tiredness
  • shakiness and unsteady walk
  • skin rash
  • slurred speech
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • sores, welting, or blisters
  • stomach pain, continuing
  • sudden decrease in the amount of urine
  • sudden numbness and weakness in the arms and legs
  • swelling of the face, fingers, or lower legs
  • swelling or inflammation of the mouth
  • swollen glands
  • tightness in the chest
  • unexplained weight loss
  • unpleasant breath odor
  • unsteadiness, awkwardness, trembling, or other problems with muscle control or coordination
  • unusual behavior, such as disorientation to time or place, failure to recognize people, hyperactivity, or restlessness
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight loss
  • vomiting of blood
  • weakness in the arms, hands, legs, or feet
  • weight gain
  • wheezing
  • yellowing of the eyes or skin

Minor Side Effects

Some norfloxacin side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:
  • Lack or loss of strength
  • Acid or sour stomach
  • belching
  • bitter taste
  • cramps
  • excess air or gas in the stomach or intestines
  • full feeling
  • heartburn
  • heavy bleeding
  • pain
  • passing gas
  • sleepiness or unusual drowsiness
  • sleeplessness
  • stomach discomfort, upset, or pain
  • unable to sleep
  • weight loss
Incidence not known:
  • Change in taste
  • continuing ringing or buzzing or other unexplained noise in the ears
  • hearing loss
  • itching of the vagina or outside genitals
  • loss of taste
  • pain during sexual intercourse
  • seeing double
  • thick, white curd-like vaginal discharge without odor or with mild odor
  • uncontrolled eye movements

For Healthcare Professionals

Applies to norfloxacin: oral tablet


Norfloxacin therapy is generally well tolerated and side effects are mild. Side effects were reported in 6.5% of subjects receiving single doses and 3.6% of subjects receiving multiple doses.[Ref]


The onset of pseudomembranous colitis symptoms may occur during or after antimicrobial treatment.

Quinolone class antibiotics have been associated with intestinal perforation and dysphasia.[Ref]

Common (1% to 10%): Nausea (2.6% to 4.2%), abdominal cramping (1.6%)
Uncommon (0.1% to 1%): Abdominal pain (0.3% to 1%), anal/rectal pain (0.3% to 1%), constipation (0.3% to 1%), diarrhea (0.3% to 1%), dry mouth/heartburn (0.3% to 1%), dyspepsia (0.3% to 1%), flatulence (0.3% to 1%), loose stools (0.3% to 1%), vomiting (0.3% to 1%), abdominal swelling (0.1% to 0.2%), mouth ulcer (0.1% to 0.2%)
Frequency not reported: Intestinal perforation
Postmarketing reports: Dysgeusia, pseudomembranous colitis, pancreatitis, stomatitis, dysphasia[Ref]

Nervous system

Seizures reported in association with norfloxacin therapy have occurred, generally in older patients. Norfloxacin should be used cautiously in patients who are predisposed to seizures. One patient with myasthenia gravis experienced a deterioration in her condition during two different courses of norfloxacin.[Ref]

Common (1% to 10%): Headache (2% to 2.8%), dizziness (1.7% to 2.6%)
Uncommon (0.1% to 1%): Tingling of the fingers (0.3% to 1%), somnolence (0.3% to 1%)
Rare (less than 0.1%): Sensory and sensorimotor axonal polyneuropathy resulting in paresthesias, hypoesthesias, dysesthesias, weakness
Postmarketing reports: Generalized seizures, myoclonus, tremors, peripheral neuropathy (may be irreversible), Guillain-Barre syndrome, ataxia, paresthesia, hypoesthesia, hearing loss, tinnitus[Ref]


Uncommon (0.1% to 1%): Allergies (0.1% to 0.2%)
Frequency not reported: Rash, systemic contact dermatitis, Stevens-Johnson syndrome, eosinophilic necrotizing granulomatous hepatitis, anaphylaxis, cardiovascular collapse, toxic epidermal necrolysis, erythema multiforme, exfoliative dermatitis, photosensitivity
Postmarketing reports: Anaphylactoid reactions, angioedema, dyspnea, vasculitis, urticaria, arthritis, arthralgia, myalgia[Ref]

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

A 71-year-old woman developed a fever and eosinophilia after 1 week of norfloxacin 400 mg three times a day. Laboratory results included an elevated white blood cell (WBC) count with 60.9% eosinophils as well as elevated hepatic transaminase levels, which returned to normal following the discontinuation of norfloxacin. Symptoms returned upon rechallenge 6 weeks later and resolved over several weeks after norfloxacin was replaced by ciprofloxacin.[Ref]


Quinolone class antibiotics have been associated with renal calculi.[Ref]

Frequency not reported: Decreased renal function, nephrotic syndrome (which has occurred in patients treated with high doses), increased BUN, increased serum creatinine, renal calculi
Postmarketing reports: Interstitial nephritis, renal failure[Ref]


Quinolone class antibiotics have been associated with hepatic necrosis.[Ref]

Common (1% to 10%): Elevated ALT (1.4%), elevated AST (1.4% to 1.6%), elevated alkaline phosphatase (1.1%)
Frequency not reported: Elevated lactate dehydrogenase, hepatic necrosis
Postmarketing reports: Hepatitis, jaundice (including cholestatic jaundice and elevated liver function tests), hepatic failure (including fatal cases)[Ref]


Common (1% to 10%): Eosinophilia (1.5%), decreased WBC (1.3% to 1.4%), decreased neutrophil count (1.4%), decreased platelet count (1%)
Uncommon (0.1% to 1%): Decreased hematocrit and hemoglobin (0.6%), increased eosinophils (0.6%)
Postmarketing reports: Leukopenia, neutropenia, hemolytic anemia, agranulocytosis, prothrombin time prolongation, thrombocytopenia[Ref]

Eosinophilia was reported in 7.5% of one 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.[Ref]


Uncommon (0.1% to 1%): Bursitis (0.1% to 0.2%)
Frequency not reported: Bilateral arthritis of the ankles, myalgia, rhabdomyolysis
Postmarketing reports: Tendonitis, tendon rupture, exacerbation of myasthenia gravis, elevated creatine kinase, muscle spasms[Ref]

Quinolones, including norfloxacin, 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 tendonitis and rupture over the general population. Quinolone use has been shown to increase that risk further in this population (12% in quinolone-treated patients vs. 7% in patients not treated).[Ref]


Common (1% to 10%): Asthenia (0.3 to 1.3%)
Uncommon (0.1% to 1%): Fever (0.3% to 1%), back pain (0.3% to 1%), foot or hand swelling (0.1% to 0.2%), bitter taste (0.1% to 0.2%), chills (0.1% to 0.2%), edema (0.1% to 0.2%)[Ref]


Uncommon (0.1% to 1%): Rash (0.3% to 1%), pruritus (0.3% to 1%), erythema (0.1% to 0.2%), urticaria (0.1% to 0.2%), pruritus ani (0.1% to 0.2%)
Frequency not reported: Erythema nodosum
Postmarketing reports: Rash, toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema multiforme, exfoliative dermatitis, leukocytoclastic vasculitis, drug rash with eosinophilia and systemic symptoms (DRESS syndrome), photosensitivity/phototoxicity reactions[Ref]

Quinolone class antibiotics have been associated with erythema nodosum.[Ref]


Common (1% to 10%): Increased urine protein (1%)
Uncommon (0.1% to 1%): Dysmenorrhea (0.1% to 0.2%), renal colic (0.1% to 0.2%)
Frequency not reported: Glycosuria
Postmarketing reports: Crystalluria, albuminuria, candiduria, cylindruria, hematuria, vaginal candidiasis[Ref]

Crystalluria has occurred in patients taking doses greater than 1200 mg/day and whose urine pH was 7.0 to 7.8.

Quinolone class antibiotics have been associated with albuminuria, candiduria, crystalluria, cylindruria, hematuria, and vaginal candidiasis.[Ref]


Uncommon (0.1% to 1%): Hyperhidrosis (0.3% to 1%)[Ref]


Uncommon (0.1% to 1%): Chest pain (0.1% to 0.2%), myocardial infarction (0.1% to 0.2%), palpitation (0.1% to 0.2%)
Postmarketing reports: Prolonged QTc interval, ventricular arrhythmia (including torsade de pointes), postural hypotension[Ref]

Quinolone class antibiotics have been associated with postural hypotension.[Ref]


Quinolone class antibiotics have been associated with nystagmus and visual disturbances.[Ref]

Uncommon (0.1% to 1%): Blurred vision (0.1% to 0.2%)
Postmarketing reports: Diplopia, uveitis, nystagmus, visual disturbances[Ref]


Quinolone class antibiotics have been associated with acidosis, symptomatic hypoglycemia, and elevations in serum triglycerides, serum cholesterol, blood glucose, and serum potassium.[Ref]

Uncommon (0.1% to 1%): Anorexia (0.1% to 1%)
Frequency not reported: Acidosis
Postmarketing reports: Symptomatic hypoglycemia, elevated serum triglycerides, elevated serum cholesterol, elevated blood glucose, elevated serum potassium[Ref]


Quinolone class antibiotics have been associated with hiccough.[Ref]

Frequency not reported: Hiccough[Ref]


Uncommon (0.1% to 1%): Anxiety (0.1% to 0.2%), depression (0.1% to 0.2%), insomnia (0.1% to 0.2%), sleep disturbances (0.1% to 0.2%)
Frequency not reported: Manic reactions
Postmarketing reports: Psychic disturbances (including psychotic reactions and confusion)[Ref]

Quinolone class antibiotics have been associated with manic reactions.[Ref]


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It is possible that some side effects of norfloxacin may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

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