What are the side effects of norfloxacin-oral?

Side effects of norfloxacin are nausea, stomach cramps, dizziness, headache, abdominal pain, diarrhea, abnormal heart beats, and photosensitivity (sun sensitivity).
Norfloxacin as well as other antibiotics in the fluoroquinolone class of antibiotics, has been associated with tendinitis and even rupture of tendons, particularly the Achilles tendon. Many antibiotics, including norfloxacin, can alter the normal bacteria in the colon and encourage overgrowth of a bacterium responsible for the development of inflammation of the colon, (C. difficile caused pseudomembranous colitis). Patients who develop signs of pseudomembranous colitis after starting norfloxacin (diarrhea, fever, abdominal pain, and possibly shock) should contact their doctor immediately.