What is the treatment and management plan for a patient diagnosed with trichomoniasis?

USMLE Step 3 CCS Case: Trichomoniasis

Case Presentation

Patient: 28-year-old female presenting with 5 days of malodorous yellow-green vaginal discharge and vulvar irritation.

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Initial Orders (Time 0)

Diagnostic Testing

• Wet mount microscopy of vaginal secretions (sensitivity 60-70%) 1
• Vaginal culture for Trichomonas vaginalis (most sensitive commercially available test) 1
• Nucleic acid amplification test (NAAT) if available (higher sensitivity than wet mount) 2
• Vaginal pH (typically >4.5 in trichomoniasis)
• Pregnancy test (urine hCG)
• HIV screening (trichomoniasis increases HIV transmission risk) 3
• Testing for co-infections: gonorrhea/chlamydia NAAT, RPR for syphilis 1

Symptomatic Management

• Avoid sexual intercourse until treatment completion 3, 4

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Treatment Orders (After Positive Diagnosis)

Primary Treatment Regimen

Metronidazole 2 g orally as a single dose 1, 3, 5

• This achieves 90-95% cure rates 1, 3
• However, the 7-day regimen (metronidazole 500 mg PO BID × 7 days) demonstrates superior efficacy (89% vs 81% cure rate) and should be strongly considered as first-line therapy 2

Alternative Regimen

• Metronidazole 500 mg PO twice daily for 7 days 1, 3, 4
• Tinidazole 2 g PO single dose (FDA-approved alternative with equivalent efficacy) 6, 7

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Critical Management Orders

Partner Management (MANDATORY)

• Treat all sexual partners simultaneously regardless of symptoms or test results 1, 3, 4
• Provide prescription for partner(s) or expedited partner therapy where legally permitted 3
• Reinfection from untreated partners is the most common cause of treatment failure 3

Patient Instructions

• Abstain from all sexual activity until both patient and partner(s) complete treatment and are asymptomatic 1, 3, 4
• Avoid alcohol during treatment and for 24-48 hours after completion (disulfiram-like reaction: nausea, vomiting, flushing, headache, abdominal cramps) 8, 4
• Complete entire course if using 7-day regimen (96% adherence reported) 2

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Follow-Up Orders

Routine Follow-Up

• No follow-up necessary if patient becomes asymptomatic after treatment 1, 3, 8

If Symptoms Persist (Treatment Failure Protocol)

First Treatment Failure:

• Re-treat with metronidazole 500 mg PO BID × 7 days 1, 3, 4
• Verify partner treatment and sexual abstinence 3

Second Treatment Failure:

• Metronidazole 2 g PO once daily × 3-5 days 1, 3, 4
• Exclude reinfection from untreated partners 3

Persistent Failure:

• Consult infectious disease specialist 1, 3, 4
• Consider susceptibility testing (contact CDC: 770-488-4115) 1

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Patient Counseling

Disease Education

• Trichomoniasis is a sexually transmitted infection caused by the protozoan Trichomonas vaginalis 1
• Most men are asymptomatic carriers but can transmit infection 1, 8
• Untreated infection increases risk of HIV acquisition and transmission 3
• In pregnancy, associated with preterm delivery, premature rupture of membranes, and low birth weight 1, 3

Medication Counseling

• Expected side effects: nausea (23%), headache (7%), vomiting (4%) 2
• Metallic taste may occur
• Absolutely no alcohol during and 24-48 hours after treatment 8, 4
• Single-dose regimen: take entire 2 g dose at once with food 5
• 7-day regimen: take 500 mg twice daily with food for full 7 days 5

Prevention Counseling

• Partner treatment is essential - provide prescription or information for partner evaluation 1, 3
• No sexual contact until both partners complete treatment and are symptom-free 3, 4
• Barrier contraception (condoms) reduces transmission risk 3
• Return if symptoms persist or recur 1

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Special Populations

If Patient is Pregnant

• Metronidazole 2 g PO single dose is safe and recommended 1, 3
• Treatment important to prevent adverse pregnancy outcomes 1, 3
• Can be given in any trimester 1

If Patient is HIV-Positive

• Use same treatment regimens as HIV-negative patients 1, 3, 8
• Treatment particularly important given increased HIV transmission risk 3

If Patient Has Metronidazole Allergy

• Desensitization protocol required (nitroimidazoles are only effective oral class) 1, 3
• Topical alternatives have <50% efficacy and are not recommended 1, 3

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Common Pitfalls to Avoid

❌ DO NOT use metronidazole vaginal gel

• Efficacy <50% for trichomoniasis (only approved for bacterial vaginosis) 1, 3, 4
• Topical preparations cannot reach urethra or perivaginal glands 1

❌ DO NOT skip partner treatment

• Even if partner is asymptomatic or has negative culture 1, 3
• Organism is difficult to isolate in men 1

❌ DO NOT assume treatment failure without excluding reinfection

• Most "failures" are actually reinfections from untreated partners 3

❌ DO NOT prescribe single-dose regimen without counseling about 7-day superiority

• Recent high-quality RCT shows 7-day regimen significantly more effective (89% vs 81% cure rate, p<0.0001) 2