Norfloxacin may have the following side effects:1. Gastrointestinal reactions, such reactions are relatively common, and may be manifested as abdominal discomfort, or pain, diarrhea, nausea, vomiting.2. Central nervous system reactions, there can be dizziness, headache, drowsiness or insomnia, etc..3. Allergic reactions, including rashes, itching of the skin, and occasionally exudative polymorphous erythema and angio- and neuroedema can occur, and a small number of patients have a Photosensitivity reaction.4. Occasionally, epilepsy, mental abnormality, irritability, disturbance of consciousness, hallucination, tremor, etc. can occur, and a part of patients may have interstitial nephritis manifestations such as hematuria, fever, rash, etc., and rare phlebitis, crystalluria, and arthralgia. A small number of patients can occur serum aminotransferase elevation, blood urea nitrogen increase, as well as peripheral blood leukocyte decrease, although most of them are mild and transient manifestations. In addition, the drug should not be used in infants and adolescents under 18 years of age, and norfloxacin should not be applied to pregnant women as well as nursing mothers.