Treatment of Trichomoniasis
The preferred first-line treatment for trichomoniasis in adults is metronidazole 500 mg orally twice daily for 7 days, which achieves cure rates of 90-95% and is superior to single-dose therapy. 1, 2, 3
First-Line Treatment Regimen
Metronidazole 500 mg orally twice daily for 7 days is the CDC-recommended preferred regimen, demonstrating superior efficacy compared to single-dose therapy with cure rates of 90-95%. 1, 2, 3
A recent high-quality randomized controlled trial (2018) directly compared these regimens and found that 7-day dosing resulted in significantly fewer treatment failures (11% vs 19%, p<0.0001), providing strong evidence for the superiority of multi-dose therapy in women. 4
Take with food to minimize gastrointestinal side effects. 5, 6
Alternative Regimen
Metronidazole 2 g orally as a single dose is an acceptable alternative when medication adherence is uncertain or cannot be assured. 1, 2, 5
While this single-dose regimen is easier to administer and ensures compliance, it has lower cure rates and should be reserved for situations where adherence to 7-day therapy is unlikely. 1, 4
The single-dose regimen remains the preferred treatment specifically in men, as the comparative efficacy data primarily come from studies in women. 7
Critical Partner Management
All sexual partners must be treated simultaneously with the same regimen to prevent reinfection—failure to treat partners is the most common cause of recurrent infection. 1, 2, 3
Patients must abstain from all sexual activity until both partners have completed treatment and are asymptomatic. 1, 2, 3
Treatment Failure Algorithm
When initial treatment fails, follow this stepwise approach:
First failure: Re-treat with metronidazole 500 mg orally twice daily for 7 days. 1, 2, 3
Second failure: Administer metronidazole 2 g orally once daily for 3-5 days. 1, 2, 3
Persistent failure: After excluding reinfection, obtain susceptibility testing and consult an infectious disease specialist. 1
Consider tinidazole (oral and/or vaginal) for refractory cases, as metronidazole-resistant T. vaginalis may be the underlying cause. 8
Special Populations
Pregnancy
Metronidazole is contraindicated during the first trimester. 1, 3, 5
After the first trimester: Use metronidazole 2 g orally as a single dose (not the 7-day regimen, as it results in higher sustained serum levels that reach fetal circulation). 1, 2, 5
Treatment is important because trichomoniasis is associated with premature rupture of membranes and preterm delivery. 1, 2
HIV-Infected Patients
Metronidazole Allergy
Desensitization is the recommended strategy, as no equally effective alternatives exist. 1, 2
Tinidazole 2 g orally as a single dose is an FDA-approved alternative 5-nitroimidazole with favorable pharmacokinetics, though cross-reactivity may occur in patients with true metronidazole allergy. 6, 9
Follow-Up Recommendations
Routine follow-up is unnecessary for patients who become asymptomatic after treatment. 1, 2, 3
Rescreening at 3 months after treatment is recommended due to high rates of repeat and persistent infections. 7
Re-evaluate only if symptoms persist, considering reinfection or resistant infection. 1, 3
Critical Pitfalls to Avoid
Never use metronidazole vaginal gel for trichomoniasis—it has efficacy <50%, is approved only for bacterial vaginosis, and fails to achieve therapeutic levels in the urethra and perivaginal glands. 1, 2, 3
Avoid alcohol during treatment and for 3 days after completing tinidazole therapy. 6
In elderly patients, monitor serum levels as metronidazole pharmacokinetics may be altered. 5
In patients with severe hepatic disease, use lower doses with close monitoring, as metronidazole accumulates in plasma. 5