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 Norfloxacin. If you are concerned about side effects, discuss the risks and benefits of Norfloxacin with your doctor.

The following side effects have been reported by at least 1% of people taking Norfloxacin. 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
• 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
• mood changes such as anxiety or Depression
• pain, swelling, or rupture of a tendon
• 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 high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• 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
• 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 Norfloxacin.

Each white, oval, biconvex, film-coated tablet, scored and engraved "APO 400" on one side and plain on the other, contains norfloxacin 400 mg. Nonmedicinal ingredients: crospovidone, magnesium stearate, colloidal silicon dioxide, hydroxypropyl cellulose, hydroxypropyl methylcellulose, polyethylene glycol, and titanium dioxide.

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

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

• Alfuzosin
• Amiodarone
• antacids containing aluminum, calcium or magnesium (do not take within 2 hours of norfloxacin)
• antipsychotics (e.g., Chlorpromazine, Clozapine, Haloperidol, Olanzapine, Quetiapine, Risperidone)
• BCG
• caffeine
• calcium supplements and multivitamins containing calcium (do not take within 2 hours of norfloxacin)
• Cholera vaccine
• chloroquine
• corticosteroids (e.g., Dexamethasone, Hydrocortisone, Prednisone)
• Cyclosporine
• diabetes medications (e.g., chlorpropamide, glipizide, Glyburide, insulin, Metformin,  Rosiglitazone)
• didanosine (do not take within 2 hours of norfloxacin)
• Disopyramide
• dofetilide
• Domperidone
• Dronedarone
• efavirenz
• Eplerenone
• Fentanyl
• Flecainide
• iron supplements, such as ferrous sulfate, or multivitamins containing iron (do not take within 2 hours of norfloxacin)
• Lanreotide
• Leuprolide
• lopinavir
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• magnesium supplements, such as magnesium sulfate, or multivitamins containing magnesium (do not take within 2 hours of norfloxacin)
• Methadone
• mifepristone
• multivitamins with minerals
• mycophenolate
• Nilotinib
• Nitrofurantoin
• nonsteroidal anti-inflammatory medications (e.g., Diclofenac, Ibuprofen, Ketoprofen, Naproxen)
• Octreotide
• Pasireotide
• Pazopanib
• Pimozide
• Porfimer
• Primaquine
• procainamide
• Quinapril
• quinidine
• quinine
• other quinolone antibiotics (e.g., ciprofloxacin, moifloxacin, sparfloxacin)
• saquinavir
• selective serotonin reuptake inhibitors (SSRIs; e.g., Citalopram, Fluoxetine, Paroxetine, Sertraline)
• serotonin antagonists (anti-emetic medications; e.g., Granisetron, Ondansetron)
• sevelamer
• sodium picosulfate
• somatostatin
• Sotalol
• Sucralfate (do not take within 2 hours of norfloxacin)
• sulfonamide antibiotics ('sulfas'; e.g., sulfisoxazole, sulfamethoxazole)
• Tetrabenazine
• theophyllines (e.g., Aminophylline, Oxtriphylline, Theophylline)
• Tizanidine
• Trazodone
• typhoid vaccine
• Varenicline
• Voriconazole
• 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 Norfloxacin. 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.

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 Norfloxacin.

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 Norfloxacin. 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 Norfloxacin may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Norfloxacin, 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 Norfloxacin 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 Norfloxacin may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Norfloxacin, 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 Norfloxacin may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Norfloxacin, 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 Norfloxacin, 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 Norfloxacin. If you have a history of Epilepsy or medical conditions that increase the risk of seizures, discuss with your doctor how Norfloxacin may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Norfloxacin, and whether any special monitoring is needed. If you have a seizure while taking Norfloxacin, 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: Norfloxacin should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Norfloxacin, contact your doctor immediately.

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

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