The adverse effects of Metronidazole are generally dose-related. The most common are gastrointestinal disturbances, especially nausea and unpleasant metallic taste, furred tongue, glossitis and stomatitis, weakness, dizziness, ataxia, headache, drowsiness, insomnia, and changes in mood or mental state such as depression or confusion have also been reported. Skin rashes, urticaria, and pruritus occur occasionally and erythema multiforme, angioedema and anaphylaxis have been reported rarely. Other side effects include urethral discomfort and darkening of the urine.