Adverse Effects of Metronidazole and Tinidazole Adverse effects of metronidazole and tinidazole include Gastrointestinal disturbances Central nervous system effects and peripheral neuropathy Disulfiram - like reaction Nausea, vomiting, headache, seizures, syncope, other central nervous system effects, and peripheral neuropathy can occur; rash, fever, and reversible neutropenia have been reported.