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Label Changes for:

Flagyl (metronidazole) 500 mg I.V. injection RTU (in plastic container)

August 2009

Changes have been made to the WARNINGS and ADVERSE REACTIONS sections of the safety label.

Detailed View: Safety Labeling Changes Approved By FDA Center for Drug Evaluation and Research (CDER) -- August 2009


  • Encephalopathy and peripheral neuropathy: Cases of encephalopathy and peripheral neuropathy (including optic neuropathy) have been reported with metronidazole.
  • Encephalopathy has been reported in association with cerebellar toxicity characterized by ataxia, dizziness, and dysarthria. CNS lesions seen on MRI have been described in reports of encephalopathy. CNS symptoms are generally reversible within days to weeks upon discontinuation of metronidazole. CNS lesions seen on MRI have also been described as reversible.
  • Peripheral neuropathy, mainly of sensory type has been reported and is characterized by numbness or paresthesia of an extremity.
  • Convulsive seizures have been reported in patients treated with metronidazole.
  • Aseptic meningitis: Cases of aseptic meningitis have been reported with metronidazole. Symptoms can occur within hours of dose administration and generally resolve after metronidazole therapy is discontinued.
  • The appearance of abnormal neurologic signs and symptoms demands the prompt evaluation of the benefit/risk ratio of the continuation of therapy.


  • most serious adverse reactions reported with injection...encephalopathy, aseptic meningitis, optic neuropathy
    • Central Nervous System: encephalopathy, aseptic meningitis, optic neuropathy...and dysarthria
    • Hypersensitivity: Urticaria, erythematous rash, Stevens-Johnson Syndrome, flushing, nasal congestion, dryness of the mouth (or vagina or vulva) and fever
  • With oral metronidazole
    • Central Nervous System:Encephalopathy, aseptic meningitis, optic neuropathy, dysarthria
    • Hypersensitivity:..Stevens-Johnson Syndrome