Trichomoniasis is caused by the protozoan T. vaginalis, which could be simply identified under the microscope of smear of discharges. Most men who are infected with T. vaginalis do not have symptoms of infection, even though a minority of men has NGU. Many women, on the other hand, do have symptoms of infection. Of these women, T. vaginalis characteristically causes a diffuse, malodorous, yellow-green discharge with vulvar irritation and many women have fewer symptoms. Premature rupture of the membranes and preterm delivery might be associated with adverse pregnancy outcomes of vaginal trichomoniasis.
Sex partners should be treated. Patients should be instructed to avoid sex until they and their sex partners are cured. In the absence of a microbiologic test of cure, this means when therapy has been completed and patient and partners are asymptomatic.
The only oral medication available in the United States for the treatment of trichomoniasis is the metronidazole. In randomized clinical trials, the recommended metronidazole regimens have resulted in cure rates of approximately 90 percent to 95 percent and ensuring treatment of sex partners might increase the cure rate. Treatment of patients and sex partners results in relief of symptoms, microbiologic cure, and reduction of transmission. Metronidazole gel is approved for treatment of BV, but, like other topically applied antimicrobials that are unlikely to achieve therapeutic levels in the urethra or perivaginal glands, it is considerably less efficacious for treatment of trichomoniasis than oral preparations of metronidazole and is not recommended for use. Several other topically applied antimicrobials have been used for treatment of trichomoniasis, but it is unlikely that these preparations will have greater effectiveness than metronidazole gel.
Infections with strains of T. vaginalis that have diminished susceptibility to metronidazole can occur. However, most of these organisms respond to higher doses of metronidazole. If treatment failure occurs with either regimen, the patient should be re-cured with metronidazole 500 mg twice a day for 7 days. If treatment failure occurs repeatedly, the patient should be treated with a single 2g dose of metronidazole once a day for 3 to 5 days. Follow up is unnecessary for men and women who become asymptomatic after treatment or who are initially asymptomatic.
Effective alternatives to therapy with metronidazole are not available. Patients who are allergic to metronidazole can be managed by desensitization.
Patients with culture-documented infection who do not respond to the regimens described in this report and in whom reinfection has been excluded should be managed in consultation with an expert. Consultation is available from CDC. Appraisal of such cases should include determination of the susceptibility of T. vaginalis to metronidazole.
It is important to know that patients who have trichomoniasis and also are infected with HIV should receive the same treatment regimen as those who are HIV-negative.

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http://wonder.cdc.gov/wonder/STD/STD98TG/STD98T10.HTM