Metronidazole (Bacterial Vaginosis)

How it works

It is reduced within anaerobic organisms to reactive intermediates that damage microbial DNA, eradicating the anaerobic overgrowth (including Gardnerella) that characterises bacterial vaginosis.

Prescribing in practice

• Counsel that systemic exposure from oral therapy (and to a lesser extent the gel) produces a disulfiram-like reaction with alcohol, so alcohol should be avoided during and just after treatment.
• Recurrence is common, and the intravaginal gel offers an option with fewer systemic side effects for women who do not tolerate oral therapy.
• Vaginal preparations may weaken latex condoms and diaphragms, reducing their contraceptive reliability.

Monitoring

No routine laboratory monitoring is needed; assess symptomatic response and consider testing for co-existing sexually transmitted infections.

Counselling the patient

• Avoid alcohol during the course and for a short time afterwards.
• Latex condoms and diaphragms may be damaged by vaginal preparations, so they cannot be relied on for contraception during use.
• Return if symptoms persist or recur, as bacterial vaginosis can come back.

Evidence & guidelines

BASHH guidance recommends oral or intravaginal metronidazole as first-line treatment for symptomatic bacterial vaginosis.