The minimum single oral metronidazole dose for treating trichomoniasis: a randomized, blinded study

Obstet Gynecol. 1997 May;89(5 Pt 1):699-703. doi: 10.1016/s0029-7844(97)81437-8.


Objective: To identify the minimum effective single oral dose of metronidazole for trichomoniasis.

Methods: Women attending an inner-city sexually transmitted disease clinic who had Trichomonas vaginalis vaginitis diagnosed by microscopy were recruited for this randomized, double-blind study. Subjects were given a 0.5-, 1-, 1.5-, or 2-g single oral dose of metronidazole, taken under direct observation. Demographic information, symptoms, and clinical findings were collected from patient interviews, and physical examinations were conducted at the time of enrollment and at the follow-up visit. The primary outcome measure was treatment success at the follow-up visit, established by negative culture and microscopy.

Results: Three (1.8%) of the 167 women enrolled were excluded because of vomiting after taking metronidazole, and 66 (40%) of the 164 remaining subjects did not return for the follow-up visit. No associations were found between the proportion of subjects lost to follow-up and the characteristics of these subjects across assignment groups. The treatment success ratio was highest in subjects who received the 1.5-g dose (23, 85%), followed by the 2-g (16, 84%), 1-g (18, 62%), and the 0.5-g dose (8, 35%).

Conclusion: A single 1.5-g dose of metronidazole has efficacy equivalent to a single 2-g dose for the treatment of T vaginalis vaginitis.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Antitrichomonal Agents / administration & dosage*
  • Antitrichomonal Agents / adverse effects
  • Double-Blind Method
  • Female
  • Follow-Up Studies
  • Humans
  • Metronidazole / administration & dosage*
  • Metronidazole / adverse effects
  • Treatment Outcome
  • Trichomonas Vaginitis / drug therapy*
  • Trichomonas Vaginitis / parasitology
  • Vomiting / chemically induced


  • Antitrichomonal Agents
  • Metronidazole