What is the best course of treatment for a male patient with green discharge and burning after intercourse, who tested negative for common sexually transmitted infections (STIs) including trichomonas, mycoplasma, and gonorrhea/chlamydia, and had a severe reaction to Flagyl (metronidazole)?

Management of Green Discharge and Burning After Intercourse with Negative STI Testing and Metronidazole Allergy

Given your negative comprehensive STI testing and severe reaction to metronidazole, you should be treated empirically with doxycycline 100 mg orally twice daily for 7 days for nongonococcal urethritis (NGU), as this covers the most common undetected causes including Ureaplasma urealyticum and atypical organisms that standard panels miss. 1

Understanding Your Clinical Picture

Your presentation of green discharge and burning with negative testing for trichomonas, mycoplasma, gonorrhea, and chlamydia is actually quite common and represents a diagnostic challenge:

• Most NGU cases have no identifiable organism on standard testing. The CDC recognizes that C. trachomatis causes only 23-55% of NGU cases, Ureaplasma urealyticum accounts for 20-40%, and Trichomonas vaginalis causes only 2-5%. 1 This means 20-50% of cases have no identified pathogen despite thorough testing. 2

• Your negative tests do not rule out infection. Standard STI panels may miss organisms like Ureaplasma urealyticum and other atypical bacteria that commonly cause urethritis. 1

Recommended Treatment Algorithm

First-Line Treatment (Since Metronidazole is Contraindicated)

Doxycycline 100 mg orally twice daily for 7 days 1, 2

• This is the CDC-recommended first-line treatment for NGU and covers the most likely undetected organisms including Ureaplasma urealyticum. 1
• The American College of Physicians endorses this as the standard empiric regimen. 1

Alternative Regimens (If Doxycycline is Not Tolerated)

If you cannot tolerate doxycycline, alternative options include:

• Erythromycin base 500 mg orally 4 times daily for 7 days, OR 1, 2
• Erythromycin ethylsuccinate 800 mg orally 4 times daily for 7 days 1, 2

If Symptoms Persist After Initial Treatment

If symptoms do not improve within 3 days of starting treatment or recur after completion: 1

1. Extended therapy with erythromycin base 500 mg orally 4 times daily for 14 days to cover possible tetracycline-resistant Ureaplasma urealyticum. 2

2. Consider non-infectious causes if symptoms persist despite two courses of appropriate antibiotics, as the CDC recognizes that persistent discharge may represent non-infectious inflammation rather than ongoing infection. 3

Critical Management Points

What You Should Know About Your Metronidazole Reaction

• Your severe reaction to metronidazole (Flagyl) is important to document, as this drug is commonly used for trichomonas and bacterial vaginosis. 4, 5
• Since your trichomonas testing was negative, avoiding metronidazole should not compromise your treatment for the current condition. 1

Partner Management

Your sexual partner(s) should be evaluated and treated empirically with the same doxycycline regimen. 1

• Partners with last sexual contact within 30 days of your symptom onset should be prioritized for treatment. 1, 2
• If you were asymptomatic initially, partners with contact within 60 days of diagnosis should be treated. 1, 2
• Abstain from sexual intercourse until both you and your partner(s) complete the full 7-day treatment course. 2

Follow-Up Expectations

• You should return for evaluation only if symptoms persist or recur after completing the full 7-day course. 1, 2
• If symptoms do not improve within 3 days of starting treatment, contact your provider for reassessment. 1
• Do not expect immediate resolution—some burning may persist for several days even with appropriate treatment. 2

Common Pitfalls to Avoid

Do Not Continue Indefinite Antibiotics

If symptoms persist after two appropriate courses of antibiotics (doxycycline followed by extended erythromycin), additional antimicrobial therapy provides minimal benefit and should be avoided. 3, 2

• The CDC emphasizes that persistent symptoms without documented infection do not warrant continued antibiotic courses. 3
• Prolonged empiric antibiotics risk adverse effects without proven benefit. 3

Do Not Assume Reinfection Without Evidence

• Persistent symptoms alone, without laboratory evidence of urethral inflammation, are not sufficient basis for retreatment. 2
• However, if you have a new sexual partner, you should be re-evaluated. 2

Recognize When Symptoms May Not Be Infectious

The CDC recognizes that some cases of persistent discharge represent non-infectious inflammation rather than ongoing infection, particularly when: 3

• Comprehensive STI testing remains negative
• Symptoms persist despite appropriate antibiotic courses
• No reinfection has occurred

In these cases, reassurance is appropriate, as the condition is not known to cause complications and is not necessarily sexually transmitted. 2