What is the recommended treatment for a sexually active female of reproductive age diagnosed with Trichomonas vaginitis from a swab test?

Treatment of Trichomonas Vaginitis

Treat with oral metronidazole 500 mg twice daily for 7 days, and simultaneously treat all sexual partners with the same regimen to prevent reinfection. 1, 2, 3

First-Line Treatment Regimen

The 7-day metronidazole course (500 mg twice daily) is superior to single-dose therapy for women, achieving 90-95% cure rates and reducing treatment failure at 1-month follow-up compared to the 2 g single dose. 1, 4, 3 This extended regimen is critical because Trichomonas persists in the urethra and perivaginal glands, requiring sustained therapeutic drug levels that single-dose therapy cannot maintain. 4, 2

Alternative Regimen

• Metronidazole 2 g orally as a single dose may be used when medication adherence is a major concern, though it has higher failure rates in women. 5, 1, 2
• Both regimens are FDA-approved and demonstrate approximately 95% cure rates in clinical trials, but the 7-day course is now preferred based on recent evidence. 5, 6

Critical Partner Management

All sexual partners must be treated simultaneously with the same metronidazole regimen, regardless of symptoms or testing status. 1, 4, 2 Male partners frequently harbor asymptomatic urethral infection that serves as a reinfection reservoir, and failure to treat partners is the most common cause of treatment failure. 4, 2

• Patients must abstain from sexual activity until both partners complete treatment and are asymptomatic. 1, 2
• Negative cultures in male partners cannot be relied upon to exclude infection due to difficulty isolating the organism. 5

Important Pitfall to Avoid

Never use topical metronidazole gel for trichomoniasis—efficacy is less than 50%. 1, 2 Vaginal preparations cannot achieve therapeutic levels in the urethra or perivaginal glands where the organism persists. 5, 2

Management of Treatment Failure

If initial treatment fails:

• First failure: Retreat with metronidazole 500 mg twice daily for 7 days, ensuring partner treatment and excluding reinfection. 1, 4, 2
• Repeated failure: Administer metronidazole 2 g once daily for 3-5 days. 5, 1, 4
• Persistent failure: Consult an infectious disease specialist and obtain susceptibility testing of T. vaginalis to metronidazole, as resistance occurs in approximately 4-5% of cases. 1, 7, 3

Follow-Up Recommendations

• Rescreen at 3 months after treatment due to high rates of reinfection and persistent infection. 3
• Routine test-of-cure is unnecessary for patients who become asymptomatic after treatment. 5, 2, 8
• A repeat Pap smear should be performed 3 months after treatment if severe inflammation was present, as Trichomonas can interfere with accurate cytological assessment. 1, 6

Special Populations

Pregnancy

• Metronidazole is contraindicated in the first trimester. 5
• After the first trimester, treat with metronidazole 2 g orally as a single dose. 4, 2, 8
• Treatment is important because trichomoniasis is associated with premature rupture of membranes, preterm delivery, and other adverse pregnancy outcomes. 5, 2, 9, 7

HIV-Positive Patients

• Use the same 7-day metronidazole regimen (500 mg twice daily) as for HIV-negative patients. 4, 2, 7
• Treatment is particularly important as T. vaginalis infection increases HIV acquisition and transmission risk. 7, 3

Metronidazole Allergy

• Effective alternatives to metronidazole are extremely limited. 5, 1
• Tinidazole may be considered for patients who fail metronidazole therapy, though it is also a nitroimidazole with potential cross-reactivity. 1, 10
• Desensitization may be required for true allergies. 2

Patient Counseling

• Advise patients to avoid alcohol during treatment and for at least 24 hours after completion due to disulfiram-like reaction causing nausea, vomiting, flushing, headache, and abdominal cramps. 2
• Emphasize that both partners must complete treatment before resuming sexual activity to prevent reinfection. 1, 2

Clinical Significance

T. vaginalis infection is associated with increased risk of HIV acquisition and transmission, adverse pregnancy outcomes including preterm birth, and potential association with cervical cancer. 1, 7, 3 The infection typically causes diffuse, malodorous, yellow-green discharge with vulvar irritation in symptomatic women, though many infections are asymptomatic. 5