## First-Line Treatment of Chlamydia trachomatis Urogenital Infection **Key Point:** Doxycycline is the gold-standard first-line agent for uncomplicated urogenital chlamydial infection in non-pregnant adults. ### Mechanism & Rationale Doxycycline is a tetracycline antibiotic that: - Inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit - Achieves excellent intracellular penetration (critical for obligate intracellular Chlamydia) - Has superior tissue distribution and urogenital bioavailability - Eradicates both the acute infection and prevents persistent infection ### Dosing & Efficacy **Doxycycline 100 mg orally twice daily for 7 days** is the CDC/WHO-recommended regimen with >95% cure rates for uncomplicated urogenital and rectal chlamydial infection. ### Treatment Guidelines Comparison | Agent | Indication | Efficacy | Notes | |-------|-----------|----------|-------| | **Doxycycline 100 mg BD × 7 days** | **Uncomplicated urogenital, rectal** | **>95%** | **First-line; excellent intracellular penetration** | | Azithromycin 1 g single dose | Uncomplicated urogenital (alternative) | 97% | Single-dose convenience; rising resistance; now 2nd-line | | Ceftriaxone 250 mg IM | Gonorrhea (not chlamydia monotherapy) | N/A | Not recommended as monotherapy for chlamydia | | Fluoroquinolone | Alternative if contraindication | 90–95% | Inferior to doxycycline; not preferred | **High-Yield:** Doxycycline is contraindicated in pregnancy (teratogenic) and children <8 years; azithromycin becomes first-line in these populations. **Clinical Pearl:** Partner notification and treatment are essential — untreated partners lead to reinfection in up to 40% of cases. **Warning:** Azithromycin resistance in C. trachomatis is rising globally; doxycycline remains the preferred agent despite azithromycin's single-dose convenience. [cite:CDC STI Treatment Guidelines 2021, Harrison 21e Ch 179]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.