What is the first-line treatment (tx) for a known single infection with Chlamydia?

First-Line Treatment for Chlamydia Infection

For a known single uncomplicated chlamydial infection in non-pregnant adults, treat with either azithromycin 1 g orally as a single dose OR doxycycline 100 mg orally twice daily for 7 days—both have equivalent efficacy of approximately 97-98%. 1, 2, 3

Treatment Selection Algorithm

Choose azithromycin 1 g single dose when: 1, 2

• Compliance with a 7-day regimen is questionable
• Follow-up is unpredictable
• The patient has erratic health-care-seeking behavior (common in young adults)
• Directly observed therapy is needed or desired
• You can dispense medication on-site and observe the first dose

Choose doxycycline 100 mg twice daily for 7 days when: 1, 2

• Cost is a primary concern (doxycycline is significantly less expensive)
• The patient can reliably complete a 7-day course
• The patient has good follow-up and medication adherence history

Critical Implementation Steps

Maximize treatment success by: 1, 2

• Dispensing medications on-site when possible
• Directly observing the first dose to ensure compliance
• Instructing patients to abstain from ALL sexual intercourse for 7 days after initiating treatment
• Ensuring abstinence continues until all sex partners have completed treatment

Partner Management (Non-Negotiable)

All sex partners from the preceding 60 days must be: 1, 2

• Evaluated and tested for chlamydia
• Empirically treated regardless of test results
• If last sexual contact was >60 days before diagnosis, still treat the most recent partner

This step is critical: Failing to treat partners leads to reinfection in up to 20% of cases, and reinfection rates can reach 39% in some adolescent populations. 1, 3

Important Caveat: Rectal Chlamydia

For rectal chlamydia specifically, doxycycline is strongly preferred over azithromycin. 4

• Azithromycin efficacy for rectal infection is only 82.9% (95% CI 76.0%-89.8%)
• Doxycycline efficacy for rectal infection is 99.6% (95% CI 98.6%-100%)
• This represents a 19.9% efficacy difference favoring doxycycline

Follow-Up Requirements

Test-of-cure is NOT recommended for non-pregnant patients treated with recommended regimens because treatment failure rates are extremely low (0-3% in males, 0-8% in females). 1, 3

However, retest ALL women at 3 months post-treatment to screen for reinfection, regardless of whether partners were reportedly treated, as repeat infections carry elevated risk for pelvic inflammatory disease and complications. 1, 2, 3

Special Populations

Pregnancy: 1, 2

• Azithromycin 1 g orally as a single dose is the preferred treatment
• Alternative: Amoxicillin 500 mg orally three times daily for 7 days
• Doxycycline is absolutely contraindicated in pregnancy
• Test-of-cure IS mandatory 3-4 weeks after treatment completion in pregnant patients

Children ≥8 years weighing >45 kg: 1, 2

• Azithromycin 1 g orally as a single dose OR
• Doxycycline 100 mg orally twice daily for 7 days

Children <45 kg: 1, 2

• Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into four doses daily for 14 days

Alternative Regimens (Only When First-Line Cannot Be Used)

The following are less desirable alternatives: 1, 2

• Levofloxacin 500 mg orally once daily for 7 days
• Ofloxacin 300 mg orally twice daily for 7 days
• Erythromycin base 500 mg orally four times daily for 7 days
• Erythromycin ethylsuccinate 800 mg orally four times daily for 7 days

Note: Erythromycin is less efficacious than azithromycin or doxycycline and has frequent gastrointestinal side effects leading to poor compliance. 1, 3

Additional STI Testing

At the initial visit, test all chlamydia-positive patients for: 2

• Gonorrhea (coinfection is common—if gonorrhea is confirmed, always treat chlamydia concurrently)
• Syphilis
• HIV