What is the recommended management of trichomoniasis, including first‑line therapy, dosing for pregnant patients, alternative regimens for metronidazole intolerance, partner treatment, and post‑treatment precautions?

Trichomoniasis Management

First-Line Treatment

Metronidazole 500 mg orally twice daily for 7 days is the preferred regimen for trichomoniasis in women, achieving superior cure rates compared to single-dose therapy. 1

• The 7-day regimen reduces treatment failure from 19% to 11% compared to single-dose therapy in the highest quality randomized controlled trial (2018, Lancet Infectious Diseases). 1
• Single-dose metronidazole 2 g orally remains an acceptable alternative when adherence to multi-day therapy is unreliable or cost is prohibitive. 2, 3
• Both regimens achieve cure rates of approximately 90-95% when partners are treated simultaneously. 2
• Metronidazole gel is NOT effective for trichomoniasis (cure rate <50%) and must never be used. 2, 4, 3

Alternative Nitroimidazoles

• Tinidazole 2 g orally as a single dose is FDA-approved and equally effective as metronidazole single-dose therapy. 5, 6
• Secnidazole 2 g orally as a single dose is newly FDA-approved with favorable pharmacokinetics including longer half-life. 7

Pregnancy-Specific Management

Pregnant patients must NOT receive treatment during the first trimester due to contraindication; defer therapy until after 12 weeks gestation. 2, 3, 8

• After the first trimester, treat with metronidazole 2 g orally as a single dose (not the 7-day regimen) to minimize total fetal drug exposure. 2, 3, 8
• Treatment is warranted after the first trimester because trichomoniasis increases risk of premature rupture of membranes, preterm delivery, and low birthweight. 3, 9
• The single-dose regimen is specifically chosen for pregnancy to limit cumulative fetal exposure while maintaining efficacy. 3

Partner Treatment (Critical)

All sexual partners must be treated simultaneously with the same metronidazole regimen regardless of symptoms—failure to do so is the most common cause of treatment failure. 2, 4, 3

• Approximately 80% of infected men are asymptomatic, making them unknowing vectors of reinfection. 9
• Partners should receive the same dose as the index patient (either 2 g single dose or 500 mg twice daily for 7 days). 3
• Patients must abstain from all sexual activity until both partners complete treatment and are asymptomatic. 2, 4, 3

Alcohol Interaction Warning

Patients must avoid all alcohol during treatment and for at least 24 hours (metronidazole) or 3 days (tinidazole) after the last dose to prevent severe disulfiram-like reactions. 4, 5

• Disulfiram-like reactions include nausea, vomiting, flushing, headache, and abdominal cramps. 4
• For patients actively consuming alcohol and unwilling to abstain, this poses a significant treatment challenge with no effective alternatives. 4

Treatment Failure Algorithm

If initial treatment fails, follow this stepwise escalation:

1. First failure: Re-treat with metronidazole 500 mg twice daily for 7 days. 2, 3
2. Second failure: Metronidazole 2 g orally once daily for 3-5 days. 2, 3
3. Persistent failure: Consult infectious disease specialist for susceptibility testing after excluding reinfection from untreated partners. 2, 3

• Most strains with diminished susceptibility still respond to higher metronidazole doses. 2
• Always confirm partner treatment before escalating therapy—reinfection is more common than true resistance. 3

Metronidazole Allergy

No effective alternatives to nitroimidazoles exist; patients with true allergy may require desensitization protocols. 2, 4, 3

Special Populations

HIV-Infected Patients

• Use the same treatment regimens as HIV-negative patients. 2, 3
• Trichomoniasis increases HIV transmission risk, making treatment particularly important. 9

Elderly Patients

• Monitor serum levels and adjust dosing as metronidazole pharmacokinetics may be altered. 8

Follow-Up

Routine follow-up is unnecessary for patients who become asymptomatic after treatment. 2, 3

• Test-of-cure is only indicated if symptoms persist, suggesting reinfection or resistance. 4

Critical Pitfalls to Avoid

• Never use topical metronidazole gel—it fails to achieve therapeutic concentrations in the urethra and perivaginal glands. 2, 4, 3
• Never treat during first trimester of pregnancy—metronidazole is contraindicated due to teratogenic concerns. 2, 3, 8
• Never fail to treat partners simultaneously—this is the primary cause of recurrent infection. 4, 3
• Never use single-dose therapy as first-line in non-pregnant women when adherence is feasible—the 7-day regimen provides superior cure rates. 1
• Never forget to counsel about alcohol avoidance—disulfiram-like reactions can be severe. 4, 5