How should I treat an adult with uncomplicated gonorrhea and chlamydia co‑infection, including dosing adjustments for patients weighing ≥150 kg, pregnant patients, doxycycline contraindications, and alternative regimens if ceftriaxone is unavailable or resistant?

Treatment for Gonorrhea and Chlamydia Co-Infection

For uncomplicated gonorrhea and chlamydia co-infection in adults, treat with ceftriaxone 500 mg intramuscularly as a single dose PLUS doxycycline 100 mg orally twice daily for 7 days. 1, 2, 3

Standard Treatment Regimen

• Ceftriaxone 500 mg IM single dose provides 99.1% cure rate for urogenital and anorectal gonorrhea, making it the most effective first-line agent 1
• Doxycycline 100 mg orally twice daily for 7 days offers superior chlamydia coverage compared to single-dose azithromycin and should be the preferred chlamydial treatment 1, 4, 2
• Co-infection occurs in 40-50% of gonorrhea cases, making presumptive dual therapy essential even when only one organism is detected 1, 5

Dosing Adjustments for Patients ≥150 kg

• For patients weighing ≥150 kg (331 lbs), increase ceftriaxone dose to 1 gram IM single dose to ensure adequate tissue concentrations 2
• Doxycycline dosing remains unchanged at 100 mg orally twice daily for 7 days regardless of body weight 4, 2

Pregnancy Modifications

Pregnant patients must receive ceftriaxone 500 mg IM single dose PLUS azithromycin 1 gram orally single dose. 6, 1, 5, 7

• Never use doxycycline, quinolones, or tetracyclines in pregnancy due to fetal safety concerns 6, 1, 5
• Azithromycin 1 gram orally or amoxicillin 500 mg orally three times daily for 7 days are the only acceptable chlamydia treatments in pregnancy 6
• Pregnant patients require test-of-cure 4 weeks after treatment, unlike non-pregnant patients 2

Alternative Regimens When Doxycycline is Contraindicated

If doxycycline cannot be used (pregnancy, age <8 years, allergy), substitute azithromycin 1 gram orally single dose for chlamydia coverage. 1, 5, 7

• Single-dose azithromycin offers convenience but has slightly lower efficacy than 7-day doxycycline for chlamydia 1
• This regimen provides true single-visit therapy: ceftriaxone 500 mg IM + azithromycin 1 gram orally, both given simultaneously 5, 7

When Ceftriaxone is Unavailable

Use cefixime 400 mg orally single dose PLUS doxycycline 100 mg orally twice daily for 7 days as the alternative regimen. 1, 5, 7

Critical Limitations of Cefixime

• Cefixime achieves only 97.4% cure rate compared to ceftriaxone's 98.9%, representing inferior efficacy 5, 7
• Mandatory test-of-cure at 1 week is required for all patients treated with cefixime-based regimens due to rising minimum inhibitory concentrations and documented treatment failures 5, 7
• Cefixime has markedly inferior efficacy for pharyngeal gonorrhea (78.9% cure rate) compared to urogenital sites 7

Alternative for Severe Cephalosporin Allergy

• Gentamicin 240 mg IM single dose PLUS azithromycin 2 grams orally single dose achieves 100% cure rate in clinical trials 7
• Azithromycin 2 grams alone has only 93% efficacy and causes significant gastrointestinal side effects (35.3% of patients), making it a poor choice 7, 8
• Never use spectinomycin for pharyngeal infections—it achieves only 52% cure rate at this site 5, 7, 9

Ceftriaxone Resistance Management

If ceftriaxone treatment failure is suspected:

• Immediately obtain specimens for culture with antimicrobial susceptibility testing from all potentially infected sites 7
• Report the case to local public health officials within 24 hours 7
• Consult an infectious disease specialist immediately 7
• Recommended salvage regimens include gentamicin 240 mg IM PLUS azithromycin 2 grams orally, or ertapenem 1 gram IM daily for 3 days 7

Site-Specific Considerations

Pharyngeal gonorrhea requires special attention:

• Ceftriaxone 500 mg IM is the only reliably effective treatment for pharyngeal infections, with superior efficacy compared to all oral alternatives 1, 5, 7
• Pharyngeal infections are significantly more difficult to eradicate than urogenital or anorectal infections 1, 5, 7
• Never use cefixime, spectinomycin, or gentamicin as monotherapy for pharyngeal exposure due to poor tissue penetration 5, 7

Critical Pitfalls to Avoid

• Never use fluoroquinolones (ciprofloxacin, ofloxacin) for gonorrhea treatment due to widespread resistance, despite historical 99.8% cure rates 1, 5, 7, 3
• Never use azithromycin 1 gram alone for gonorrhea—it has only 93% efficacy and risks rapid resistance emergence 1, 5, 7, 8
• Never use cefixime without mandatory test-of-cure at 1 week due to declining effectiveness 5, 7
• Never omit chlamydia treatment even when chlamydia testing is negative in a patient with confirmed gonorrhea, due to 40-50% co-infection rates 1, 7

Follow-Up Requirements

• Patients treated with recommended ceftriaxone + doxycycline or azithromycin regimens do NOT need routine test-of-cure unless symptoms persist 1, 5, 7
• All patients should be retested 3 months after treatment due to high reinfection rates (not treatment failure) 1, 5, 7, 2
• If symptoms persist after treatment, obtain culture with antimicrobial susceptibility testing immediately 7

Partner Management

• All sexual partners from the preceding 60 days must be evaluated and treated with the same dual therapy regimen, regardless of symptoms or test results 1, 5, 7
• Partners should receive ceftriaxone 500 mg IM + doxycycline 100 mg twice daily for 7 days (or azithromycin 1 gram if single-dose preferred) 1, 7
• Patients and partners must abstain from sexual intercourse until therapy is completed and both are asymptomatic 5, 7
• Expedited partner therapy with oral cefixime 400 mg + azithromycin 1 gram may be considered when partners cannot access timely evaluation, except in men who have sex with men due to high risk of undiagnosed HIV or other STIs 7

Additional Screening

• Perform serologic screening for syphilis at the time of gonorrhea diagnosis due to overlapping risk factors and high co-infection rates 5, 7
• Co-testing for HIV should be performed given that gonorrhea facilitates HIV transmission 7