Norfloxacin is an antibiotic that belongs to the class of medications called quinolones. It is used to treat infections caused by certain types of bacteria. It is most commonly used to treat urinary tract (bladder) infections. It is also used to treat gonorrhea, a sexually transmitted infection. Norfloxacin works by killing some types of bacteria that can cause these infections.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

For the treatment of urinary tract infections, the usual recommended adult dose is 400 mg twice daily, taken with a glass of water at least one hour before or 2 hours after a meal or milk. You should drink plenty of liquids (water or juice) every day unless your doctor has told you otherwise.

For the treatment of gonorrhea, the usual recommended adult dose is 800 mg (two 400 mg tablets) given as a single dose.

Norfloxacin should not be taken within 2 hours of taking iron, zinc supplements, or multivitamins containing them. The dose of norfloxacin can vary depending on the circumstances and the condition being treated.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the one above, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. Finish all this medication, even if you have started to feel better. If you miss a dose, take it as soon as possible and continue on with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue on with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not take norfloxacin if you are allergic to norfloxacin, other quinolones (e.g., ciprofloxacin, nalidixic acid), or any other ingredients of the medication.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• diarrhea (mild)
• dizziness or lightheadedness
• headache
• heartburn
• increased skin sensitivity to the sun
• loss of appetite
• nausea
• nightmares
• trouble sleeping
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• anxiety
• blistering of skin
• hallucinations (hearing or seeing things that aren't there)
• increasing muscle weakness
• joint or muscle pain
• memory loss
• nervousness
• pain, swelling, or rupture of a tendon
• restlessness
• sensation of skin burning, tingling or numbness
• signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• skin itching, rash, redness, or swelling
• symptoms of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
• symptoms of low blood sugar (e.g., cold sweat, cool pale skin, headache, fast heartbeat, weakness)
• vision changes

Stop taking the medication and seek immediate medical attention if any of the following occur:

• diarrhea (watery and severe or bloody)
• seizures
• severe abdominal, back, or chest pain
• signs of a serious allergic reaction (swelling of face or throat, hives, or difficulty breathing)
• signs of pancreatitis (e.g., abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, swollen abdomen)
• signs of a severe skin reaction (e.g., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)
• thoughts of suicide or self-harm

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Aortic aneurysm: There have been rare reports of problems with enlargement or bulging of the aorta, the large blood vessel that carries blood out of the heart to the rest of the body. If you experience sudden severe abdominal, back or chest pain, fainting, dizziness or a pulsing sensation in the abdomen, get immediate medical attention.

Bacterial resistance: Misuse of an antibiotic such as norfloxacin may lead to the growth of resistant bacteria that will not be killed by the antibiotic. If this happens, the antibiotic may not work for you in the future. Although you may begin to feel better early in your course of treatment with norfloxacin, you need to take the full course exactly as directed to finish ridding your body of the infection and to prevent resistant bacteria from taking hold. Do not take norfloxacin or other antibiotics to treat a viral infection such as the common cold; antibiotics do not kill viruses, and using them to treat viral infections can lead to the growth of resistant bacteria.

Blood sugar levels: Norfloxacin may cause a loss of control of blood sugar levels and glucose tolerance may change. People with diabetes may find it necessary to monitor their blood sugar more frequently while using this medication. People without diabetes have also been known to experience high or low blood sugars while taking norfloxacin.

If you have diabetes or are at risk for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you experience signs of high blood sugar (fruity breath odour, weight loss, increased thirst, or increased need to urinate) or low blood sugar (cold sweat, cool pale skin, headache, or weakness) contact your doctor.

Diarrhea: People taking this medication may develop diarrhea caused by an infection with the bacteria C. difficile. If you have loose, watery and bloody bowel movements, with or without fever or stomach cramps, after taking norfloxacin, get medical attention as soon as possible. Diarrhea caused by C. difficile infection can lead to serious health problems if it is not properly treated.

Kidney: Norfloxacin is passed from the body mostly by the kidney. If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Neuromuscular disorders: Norfloxacin may cause increased muscle weakness for people with myasthenia gravis (an autoimmune disorder that causes muscle weakness). If you have myasthenia gravis, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Nervous System: Although rare, norfloxacin has been reported to cause problems with the nervous system, including nerve damage in the hands and feet, and changes in mental health. These side effects can occur while taking norfloxacin or after completing treatment with norfloxacin. If you experience tingling, numbness, weakness or other sensation changes while taking or after stopping this medication, contact your doctor as soon as possible. Other changes that should be reported to your doctor immediately, include agitation, hallucinations, confusion, depression or thoughts or suicide or self-harm.

Seizures: Rarely, seizures have been reported with this medication. If you have a history of epilepsy or medical conditions that increase the risk of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you have a seizure while taking this medication, stop taking it and get immediate medical attention.

Sunburn: People who take norfloxacin are more likely to suffer from sunburn. Avoid exposure to excessive sunlight, including sunlamps and tanning beds, and use sunblock with minimum SPF 15. Stop taking the medication if sun sensitivity occurs.

Tendons: Rarely, people taking norfloxacin have experienced tendonitis and/or tendon rupture, especially if they were also taking corticosteroids. This can happen at any time while taking norfloxacin or after finishing the medication. Tendonitis can continue for a lengthy period of time and be disabling. If you experience any joint or tendon pain or swelling, contact your doctor as soon as possible. If you have experienced this effect as a result of taking norfloxacin or another similar antibiotic in the past, norfloxacin should be avoided.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Norfloxacin may pass into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children less than 16 years of age.

There may be an interaction between norfloxacin and any of the following:

• acetylsalicylic acid (ASA)
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• antacids containing aluminum, calcium or magnesium (do not take within 2 hours of norfloxacin)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• BCG
• bromocriptine
• caffeine
• calcium supplements and multivitamins containing calcium (do not take within 2 hours of norfloxacin)
• celecoxib
• cholera vaccine
• corticosteroids (e.g., dexamethasone, hydrocortisone, prednisone)
• cyclosporine
• diabetes medications (e.g., acarbose, canagliflozin,  glyburide, insulin, linagliptin, lixisenatide, metformin, rosiglitazone)
• disopyramide
• dronedarone
• fludrocortisone
• iron supplements, such as ferrous sulfate, or multivitamins containing iron (do not take within 2 hours of norfloxacin)
• leflunomide
• magnesium supplements, such as magnesium sulfate, or multivitamins containing magnesium (do not take within 2 hours of norfloxacin)
• methadone
• methylphenidate
• mifepristone
• multivitamins with minerals
• mycophenolate
• nitrofurantoin
• nonsteroidal anti-inflammatory medications (e.g., diclofenac, ibuprofen, ketorolac, naproxen)
• procainamide
• quinidine
• other quinolone antibiotics (e.g., ciprofloxacin, moxifloxacin,)
• sevelamer
• sodium picosulfate
• somatostatin-like medications (e.g., lanreotide, octreotide, pasireotide)
• sotalol
• sucralfate (do not take within 2 hours of norfloxacin)
• sulfonamide antibiotics ('sulfas'; e.g., sulfisoxazole, sulfamethoxazole)
• sunitinib
• teriflunomide
• theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
• tramadol
• typhoid vaccine
• warfarin
• zinc supplements or multivitamins containing zinc (do not take within 2 hours of norfloxacin)

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.