Worst Pills, Best Pills

An expert, independent second opinion on more than 1,800 prescription drugs, over-the-counter medications, and supplements

Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Limited Use [what does this mean?]
Generic drug name: norfloxacin (nor FLOX a sin)
GENERIC: available FAMILY: Fluoroquinolones
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Fluoroquinolones caused fetal harm in animal studies, including decreased body weights and malformed bones as well as an increased risk of death. Because of the potential for serious adverse effects to the fetus, these drugs should not be used by pregnant women.

Breast-feeding Warning

Fluoroquinolones are excreted in human milk. Because of the potential for serious adverse effects in nursing infants, you should not take these drugs while nursing.

Safety Warnings For This Drug [top]

Warning: Peripheral Neuropathy

Rare cases of sensory or sensorimotor axonal polyneuropathy affecting small and/or large axons resulting in paresthesias, hypoesthesias, dysesthesias (abnormal sensation) and weakness have been reported in patients receiving quinolones, including [name of fluoroquinolone antibiotic]. [Name of fluoroquinolone antibiotic] should be discontinued if the patient experiences symptoms of neuropathy including pain, burning, tingling, numbness, and/or weakness, or is found to have deficits in light touch, pain, temperature, position sense, vibratory sensation, and/or motor strength in order to prevent the development of an irreversible condition. 

Antibiotic-Associated Diarrhea

Antibiotic-associated diarrhea (AAD) is quite common and its incidence varies from 5% to 20% of patients depending on which antibiotic they are taking, although practically all antibiotics have been associated with AAD. Fortunately, most cases are mild and self-limited, ending with the cessation of use of the offending antibiotic. The antibiotics most commonly associated with this mild form of AAD include ampicillin, amoxicillin, cephalosporins and clindamycin.[1] There have been studies in children or adults in which the use of prophylactic yogurt in people using antibiotics has significantly reduced the occurrence or severity of AAD.[2],[3] However, 10% to 20% of all patients who get AAD (0.5% to 4% of patients using antibiotics) will get the more severe form of AAD known as pseudomembranous colitis (see below). If you are taking any antibiotic and develop diarrhea after starting to use the drug, call your physician to discuss whether another antibiotic should be used and to discuss the need for rehydration due to the fluid loss from the diarrhea.

Pseudomembranous colitis has been reported with nearly all antibacterial agents and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents.

Because antibiotic therapy has been associated with severe colitis, which may end fatally, it should be reserved for serious infections where less toxic antimicrobial agents are inappropriate, as described in the INDICATIONS AND USAGE section. It should not be used in patients with nonbacterial infections such as most upper respiratory tract infections. Treatment with antibacterial agents alters the normal flora of the colon and may permit over-growth of clostridia. Studies indicate that a toxin produced by Clostridium difficile is one primary cause of "antibiotic-associated colitis."

After the diagnosis of pseudomembranous colitis has been established, therapeutic measures should be initiated. Mild cases of pseudomembranous colitis usually respond to drug discontinuation alone. In moderate to severe cases, consideration should be given to management with fluids and electrolytes, protein supplementation, and treatment with an antibacterial drug that is clinically effective against C. difficile colitis.

Diarrhea, colitis, and pseudomembranous colitis have been observed to begin up to several weeks following cessation of therapy.

FDA Myasthenia Gravis Boxed Warning

Fluoroquinolone products may exacerbate muscle weakness in persons with myasthenia gravis. Avoid fluoroquinolone products in a patients with a known history of myasthenia gravis.[4]

Facts About This Drug [top]

Norfloxacin is no longer marketed in the U.S., either because it was withdrawn for safety reasons or its manufacturer discontinued its production.

Norfloxacin (CHIBROXIN, NOROXIN) kills bacteria and can cure infections caused by susceptible organisms. Oral norfloxacin differs from the other fluoroquinolone antibiotics — such as ciprofloxacin (CIPRO) and levofloxacin (LEVAQUIN) — in that it is used to treat only infections in the urinary tract and prostate gland and sexually transmitted...

Norfloxacin is no longer marketed in the U.S., either because it was withdrawn for safety reasons or its manufacturer discontinued its production.

Norfloxacin (CHIBROXIN, NOROXIN) kills bacteria and can cure infections caused by susceptible organisms. Oral norfloxacin differs from the other fluoroquinolone antibiotics — such as ciprofloxacin (CIPRO) and levofloxacin (LEVAQUIN) — in that it is used to treat only infections in the urinary tract and prostate gland and sexually transmitted infections.[5] Drops of norfloxacin are used to treat eye infections.

Elderly people have suffered more severe adverse effects, fatalities and harmful interactions from norfloxacin.[6],[7] Because norfloxacin is excreted more slowly in people older than 65 years, a lower dose is usually prescribed for these patients.

Resistance or allergy to one drug in this family usually indicates resistance or allergy to the rest of the fluoroquinolones.[8],[9] Overgrowth of normal bacteria may cause yeast infections, especially when antibiotics are used for long periods.

As a group, fluoroquinolones are expensive, and resistance to the drugs is increasing. However, effective alternatives are available.[10] A seven-day course of norfloxacin costs five to 10 times more than drugs such as amoxicillin or trimethoprim and sulfamethoxazole, which are equally effective for most infections.

The safety and efficacy of oral norfloxacin in pediatric patients, adolescents (under the age of 18), pregnant women and nursing mothers have not been established.

In 2008, the European Medicines Agency recommended that the use of medicines containing oral norfloxacin be restricted for treatment of urinary infections. The agency based its decision on evidence that the benefits of these medicines do not outweigh their risks for this indication and that efficacy has not been adequately demonstrated for this type of infection.[11]

Adverse effects

The adverse effects associated with norfloxacin can result from either the oral tablets or eye drops.

Fluoroquinolones can cause central nervous system reactions and psychosis.[8] Severe, even fatal, allergic reactions have occurred after one dose. Collapse of the circulatory system also has occurred.

On rare occasions, prolonged QTc intervals and ventricular arrhythmia, including torsades de pointes, have been reported. Norfloxacin should be avoided in patients receiving class IA (quinidine, procainamide) or class III (amiodarone, sotalol) antiarrhythmic agents.

Peripheral neuropathy and tendon ruptures have been reported in patients receiving fluoroquinolones. The Food and Drug Administration (FDA) now requires that the professional product labeling, or package inserts, for all fluoroquinolone antibiotics must warn about the possibility of peripheral neuropathy (nerve damage) and tendon rupture.

Antibiotic-associated diarrhea (AAD) is an adverse effect of antibiotic treatment. A report appearing in 2005 in the Canadian Medical Association Journal estimated that as many as 2,000 patients may have died from AAD in Quebec hospitals since 2003.[12] Many different types of antibiotics can cause AAD, but reports have recently implicated use of drugs in the fluoroquinolone family of antibiotics as an important risk factor in the development of a potentially life-threatening form of AAD called pseudomembranous colitis.

Retinal detachment

A study in the Journal of the American Medical Association found that patients taking oral fluoroquinolones appear to have an increased risk of developing retinal detachment, a medical emergency that can result in permanent vision loss unless promptly treated by an ophthalmologist. The authors of this study estimated that as many as 1,400 cases of retinal detachment each year in the U.S. may be caused by the use of these drugs.[13]

In 2013, a study conducted in diabetic patients found an increased risk of dysglycemia (abnormal blood glucose levels) in diabetic patients using oral fluoroquinolones.[14]


As of Jan. 15, 2004, Health Canada, the Canadian equivalent of the FDA, had received 57 reports of suspected interactions associated with fluoroquinolones and the oral anticoagulant warfarin. If you take warfarin and are prescribed a fluoroquinolone antibiotic, ask your doctor what tests should be performed to monitor your blood coagulation levels.[15]

Practice prevention

Urinary tract infections

Practice measures to prevent urinary tract infections. Drink plenty of fluids, especially water.

Restrict caffeine, which widens the urethra. Indwelling catheters can cause urinary tract infections.

Women are particularly prone to repeated urinary tract infections. If urinary tract symptoms occur often, ask your doctor about keeping a supply of medication on hand. Ideally, the antibiotic you use should be the most effective, least toxic and least costly option available.[16],[17] Practice meticulous hygiene. After using the toilet, wipe backward, not forward, and then wash your hands.


Prepare and store foods properly, especially when traveling, to prevent diarrhea.

Regulatory actions surrounding norfloxacin

2008: The FDA updated the patient package insert (PPI) on fluoroquinolones to include a boxed warning with information about the increased risk of developing tendinitis and tendon rupture. The FDA also required manufacturers to develop a Medication Guide for patients. This boxed warning strengthens the already existing information on tendinitis and tendon rupture in the PPI.[18]

2011: The FDA added a boxed warning to the fluoroquinolone group of drugs stating that, when fluoroquinolones are used in patients with myasthenia gravis (a disease that causes muscle weakness), the drugs may exacerbate muscle weakness.[4]

The 2011 warning also requires that a Medication Guide about this risk be provided to patients.

2018: The FDA updated the product labels of fluoroquinolones to warn that fluoroquinolone use was associated with an increased risk of aortic aneurysm or dissection, which can lead to bleeding and death.[19]

2020: In December, the Medicines and Healthcare products Regulatory Agency (MHRA, a regulatory agency in the U.K. similar to the FDA) issued an advisory that fluoroquinolones are associated with a small risk of a heart valve defect called heart valve regurgitation, which occurs when the heart valves do not close completely, allowing blood to flow in the wrong direction.[20] Such heart valve problems may lead to heart failure.

Before You Use This Drug [top]

Do not use if you have or have had:

  • allergies to fluoroquinolones or quinolone-type drugs
  • photosensitivity
  • inflammation or rupture of tendons

Tell your doctor if you have or have had:

  • allergies to drugs
  • epilepsy or seizures
  • liver problems
  • kidney problems
  • myasthenia gravis[21]
  • an implanted metal device[22]
  • brain or spinal cord disease
  • heart disorder
  • diabetes
  • low potassium blood level
  • pregnancy or are breast-feeding

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products. It is especially important you tell your doctor if you take any heart drug.

When You Use This Drug [top]

  • Check with your doctor if there is no improvement of symptoms within a few days.
  • Do not drive or perform other activities that require alertness because this drug may make you drowsy, dizzy, or lightheaded.
  • If you plan to have any surgery, including dental, tell your doctor that you take this drug.
  • Protect yourself from sunburn. Do not use a sunlamp.
  • If you get a skin reaction to the sun, avoid further sunlight and artificial light until reaction has stopped or for five days, whichever is longer.
  • Call your doctor and discontinue the drug if you get pain, inflammation, or rupture of a tendon.
  • Caution diabetics: Call your doctor and discontinue drug if you have a hypoglycemic episode.
  • For oral forms of this drug: Do not take this drug and antacids or sucralfate (CARAFATE) at the same time. You have to wait two hours after taking an antacid or sucralfate before you can take norfloxacin; you also have to wait two hours after taking norfloxacin before you can take an antacid or sucralfate.
  • Call your doctor and discontinue the drug if you get pain, inflammation, or rupture of a tendon.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Take this drug for the prescribed length of time. If you stop too soon, your symptoms could come back.
  • Drink plenty of fluids.
  • Take with a full glass (eight ounces) of water.
  • Take with or without food.
  • Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

aluminum hydroxide, AMPHOJEL, caffeine (beverages, drugs), CARAFATE, cyclosporine, FEOSOL, FERGON, ferrous gluconate, ferrous sulfate, MAALOX, magnesium hydroxide, NEORAL, PHILLIPS’ MILK OF MAGNESIA, SANDIMMUNE, SLOW FE, sucralfate.

A report in the Archives of Internal Medicine adds interaction with COUMADIN (warfarin) as the one most frequently reported in older people.[7]

Caution should be taken when the following drugs are used with this one (see warning box): aminophylline, ELIXOPHYLLIN, SLO-BID, SOMOPHYLLIN, SOMOPHYLLIN-DF, THEO-24, theophylline.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • severe or bloody diarrhea
  • agitation
  • difficulty breathing
  • confusion, hallucinations
  • fever
  • skin rash, itching, redness, or peeling
  • seizure
  • swelling of face, neck, calves, or lower legs
  • tremors
  • blurred vision
  • pain at site of injection
  • pain in calves radiating to heels
  • heartbeat change

Call your doctor if these symptoms continue:

  • dizziness, lightheadedness
  • drowsiness
  • headache
  • insomnia, restlessness
  • nausea or vomiting
  • diarrhea
  • pain in abdomen, stomach, or joints
  • increased sensitivity of skin to sunlight

<> Call your doctor if these symptoms continue after you stop taking this drug:


  • severe abdominal or stomach cramps
  • abdominal tenderness
  • watery and severe diarrhea
  • pain in calves radiating to heels
  • sensation of skin burning
  • skin rash, itching, redness, or peeling
  • swelling of face, neck, calves, or lower legs

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

  • bleeding times

last reviewed October 31, 2023