Metallic Taste from Metronidazole: Frequency and Duration
Yes, bad taste in the mouth is a common side effect of oral metronidazole, occurring in approximately 8-18% of patients, and typically resolves within 3-5 days of onset or shortly after completing the medication course.
Frequency of Taste Disturbance
Metallic taste is explicitly recognized as a common adverse effect in the FDA drug label, described as "a sharp, unpleasant metallic taste is not unusual" with oral metronidazole 1
Clinical trial data demonstrates that metallic taste occurs in approximately 17.9% of patients taking oral metronidazole, compared to only 8.8% with intravaginal formulations 2
In comparative studies, taste-related adverse events were significantly more common with oral metronidazole than with intravaginal gel formulations 3
The CDC guidelines acknowledge this side effect as one reason some providers prefer intravaginal routes, noting that systemic side effects including "unpleasant taste" are avoided with topical formulations which achieve less than 2% of oral serum concentrations 4
Duration of Symptoms
Most metronidazole-associated side effects, including taste disturbances, begin within 3 days of starting treatment and resolve within 5 days of onset 5
The metallic taste typically persists during the treatment course and resolves shortly after medication discontinuation 1, 2
In a prospective study of 155 women taking oral metronidazole 400mg twice daily for 7 days, 64% reported at least one adverse effect, with most symptoms resolving within days and having limited impact on treatment completion 5
Clinical Significance and Management
The taste disturbance rarely leads to treatment discontinuation, with only 3-8% of patients stopping metronidazole due to adverse effects overall 5
For patients who find the metallic taste intolerable, switching to intravaginal metronidazole gel reduces the incidence of taste disturbance by more than 50% (from 17.9% to 8.8%) while maintaining equivalent efficacy 2
The British Society of Gastroenterology notes that taste disturbance is a recognized cause of poor compliance with nitroimidazole antibiotics like metronidazole, particularly when used for extended periods 4
Important Counseling Points
Patients should be informed that metallic taste is a common, expected side effect that does not indicate treatment failure or toxicity 1
The symptom is self-limited and will resolve after completing or discontinuing the medication 5
Alcohol consumption during treatment may worsen taste alterations, as the CDC warns patients to avoid alcohol during metronidazole therapy and for 24 hours after 4, 6, 7
If taste disturbance is severe enough to compromise compliance, alternative formulations (intravaginal gel) or alternative antibiotics (clindamycin) should be considered 4, 6