What is the recommended first‑line therapy for Trichomonas vaginalis infection, including options for pregnant patients and partner management?

Treatment for Trichomoniasis

For non-pregnant women, metronidazole 500 mg orally twice daily for 7 days is now the preferred first-line treatment, as it achieves superior cure rates (89%) compared to the traditional single 2g dose (81% cure rate). 1, 2

First-Line Treatment Regimens

Non-Pregnant Women

• Metronidazole 500 mg orally twice daily for 7 days is the recommended regimen, with cure rates of 89% 1, 2
• This multi-dose regimen significantly reduces treatment failure compared to single-dose therapy (11% failure vs 19% failure, p<0.0001) 1
• The alternative single-dose regimen (metronidazole 2g orally once) achieves only 81% cure rates and should be reserved for situations where compliance with multi-day therapy is unreliable 1, 2

Men

• Metronidazole 2g orally as a single dose remains the preferred treatment 2
• Alternative: Metronidazole 500 mg twice daily for 7 days 3
• Most infected men are asymptomatic but serve as vectors for reinfection 4

Pregnant Women

• Metronidazole is absolutely contraindicated during the first trimester due to concerns about fetal organogenesis 3, 4, 5
• After the first trimester: Metronidazole 2g orally as a single dose (not the 7-day regimen) to minimize total fetal drug exposure 3, 4, 6
• Treatment after the first trimester is warranted because trichomoniasis is associated with premature rupture of membranes and preterm delivery 3, 4
• If symptomatic during first trimester, treatment must be delayed until second trimester begins 4

Critical Partner Management

All sexual partners must be treated simultaneously with the same metronidazole regimen, regardless of symptoms 3, 4, 6

• Failure to treat partners is the most common cause of treatment failure and reinfection 4
• Patients must abstain from all sexual intercourse until both partners complete treatment and are asymptomatic 3, 4, 6
• Most infected men are asymptomatic carriers, making partner treatment essential even without confirmed testing 4

Treatment Failure Management

First Failure

• Re-treat with metronidazole 500 mg twice daily for 7 days 3, 4

Second Failure

• Metronidazole 2g orally once daily for 3-5 days 3, 4

Persistent Failure

• Consult infectious disease specialist for susceptibility testing 3, 4
• Exclude reinfection from untreated partners before escalating therapy 3
• Consider tinidazole (oral and vaginal combination) for metronidazole-resistant strains 7
• In vitro metronidazole resistance remains low (4.3%) but should be monitored 2

Important Safety Considerations

• Patients must avoid all alcohol during treatment and for at least 24 hours after the last dose to prevent severe disulfiram-like reactions 4
• Metronidazole gel is NOT effective for trichomoniasis (achieves <50% efficacy) and should never be used 3, 4
• Other topical antimicrobials have even lower cure rates (<50%) and are not recommended 3, 4

Follow-Up

• Follow-up is unnecessary for patients who become asymptomatic after treatment 3, 4, 6
• Rescreening at 3 months after treatment is recommended due to high rates of repeat and persistent infections 2

Special Populations

HIV-Infected Patients

• Receive the same treatment regimen as HIV-negative patients 3, 4, 6

Metronidazole Allergy

• No effective alternatives exist 3
• Patients can be managed by desensitization 3

Common Pitfalls to Avoid

• Do not use single-dose therapy in non-pregnant women unless compliance with multi-day therapy is impossible—the 7-day regimen is significantly more effective 1, 2
• Do not treat pregnant women during first trimester—delay until second trimester 3, 4, 5
• Do not use metronidazole gel—it does not achieve therapeutic levels in the urethra or perivaginal glands 3, 4
• Do not fail to treat partners—this is the primary cause of treatment failure 4
• Do not forget alcohol avoidance counseling—disulfiram-like reactions can be severe 4