Intravaginally applied metronidazole is as effective as orally applied in the treatment of bacterial vaginosis, but exhibits significantly less side effects.

OBJECTIVE Metronidazole is the drug of choice for the treatment of bacterial vaginosis (BV). However, so far the oral administration has not been clinically compared to the intravaginal application regarding efficacy, side effects and patient satisfaction in a scientific sound fashion. STUDY DESIGN Therefore, this randomized, double-blind, placebo-controlled clinical trial was designed to demonstrate non-inferiority of short-term intravaginal (i.vag.) application of metronidazole (2x 1000 mg pessaries 24h apart) vs. a single oral dose (p.o.) of metronidazole (1 x 2000 mg tablets) in 263 patients with BV (double-dummy design). The follow-up period was 12 weeks. In addition, the number and the type of adverse events induced by the two regimens were compared, assuming better tolerability of the intravaginal application. RESULTS Following the diagnosis of BV a total of 129 women (mean age 36.2 years) was orally treated with a single dose of 2g metronidazole whereas a total of 134 patients (mean age 35.5 years) was treated intravaginally with 1g metronidazole each day on two consecutive days and included in the per-protocol analysis. Non-inferiority of i.vag. application compared to p.o. administration was statistically significant regarding efficacy: Following intravaginal application the cure rate, assessed on day 8 after starting of the treatment, was 92.5% as compared to 89.9% after oral administration. Nausea was the most common adverse event reported in 10.2% i.vag. vs. 30.4% p.o. of all cases (p<0.001), abdominal pain in 16.8% i.vag. vs. 31.9% p.o. (p<0.01), a "metallic taste" in 8.8% i.vag. vs. 17.9% p.o. (p<0.05). Women treated i.vag. were highly satisfied with the treatment and more content as compared to the women treated p.o. with metronidazole (p<0.05, intent-to-treat analysis). CONCLUSION In this clinical trial the intravaginal application was as effective as the oral administration of metronidazole in treating BV. However, significantly less adverse events were reported after short-term intravaginal as compared to oral application (p=0.023) and probably led to a better patient compliance.