Although very rarely, the possible adverse reactions (in gel administration) are: Hypersensitivity: Hypersensitivity reactions with chills, fever, erythema and maculopapular rash may develop after administration of a single dose of metronidazole in patients who have had a history of itching or rash during metronidazole intravaginal therapy. Dryness and burning sensation in the vagina. Skin itching, urticaria and pruritus is frequent, while erythema multiforme, angioedema and anaphylaxis are rarely reported.
Common side effects are gastrointestinal disturbances eg, nausea, metallic taste and occasionally, vomiting and anorexia. Diarrhea, dry mouth, furred tongue, glossitis and stomatitis may occur. Pseudomembranous colitis is reported rarely.
Peripheral neuropathy, characterized by numbness or tingling during extreme attacks, and seizures are serious side effects which may occur on high-dose or prolonged use of metronidazole.
Mild and transient leucopenia and thrombocytopenia may occur in some patients.
Increased liver enzymes, hepatitis and cholestatic jaundice.