Infectious Disease · Topic 10 of 10

Sexually Transmitted Infections & PID

Infectious disease · sexually transmitted infections

Sexually Transmitted Infections & PID

Ceftriaxone 500 mg IM for gonorrhea, doxycycline for chlamydia, benzathine penicillin for syphilis — and treat the partners, then retest in 3 months.

Key numbers

Ceftriaxone 500 mg IM for gonorrhea500 mg IM once

Doxycycline 100 mg BID for chlamydia7 days

Benzathine penicillin G 2.4 million units IM2.4 MU IM

PID: ceftriaxone + doxycycline + metronidazole14 days

Neurosyphilis or ocular syphilis: IV aqueous penicillin G18–24 MU/day IV

01 · GiveCeftriaxone 500 mg IM for gonorrhea

Uncomplicated gonorrhea of the cervix, urethra, rectum or pharynx: ceftriaxone 500 mg IM as a single dose (1 g if the patient weighs ≥ 150 kg).

02 · GiveDoxycycline 100 mg BID for chlamydia

Chlamydia: doxycycline 100 mg orally twice daily for 7 days; alternatives are azithromycin 1 g once or levofloxacin 500 mg daily for 7 days, and azithromycin 1 g is the regimen in pregnancy.

03 · GiveBenzathine penicillin G 2.4 million units IM

Primary, secondary and early latent syphilis: benzathine penicillin G 2.4 million units IM once; late latent or unknown-duration syphilis: 2.4 million units IM weekly for 3 weeks (7.2 million units total).

Diagnosis & monitoring

Work-up

Pelvic organ tenderness: treat empirically for PID must knowStart presumptive PID treatment in a sexually active patient with pelvic or lower abdominal pain and no other cause when the exam shows cervical motion, uterine or adnexal tenderness.

Follow RPR titers for a fourfold fallRecheck nontreponemal (RPR or VDRL) titers at 6 and 12 months and expect a fourfold decline; treponemal tests usually stay positive for life and cannot monitor treatment.

Test every syphilis patient for HIVTest everyone with syphilis for HIV at diagnosis and offer HIV PrEP to those who test negative.

Retest 3 months after treatmentRetest patients treated for gonorrhea or chlamydia about 3 months after treatment, whether or not they believe their partners were treated — reinfection is common.

Test of cure: pharyngeal gonorrhea, chlamydia in pregnancyTest of cure is needed only for pharyngeal gonorrhea (7–14 days after treatment) and for chlamydia in pregnancy (about 4 weeks after therapy), not for uncomplicated urogenital or rectal infection.

Management

Orders

PID: ceftriaxone + doxycycline + metronidazole must knowOutpatient PID: ceftriaxone 500 mg IM once plus doxycycline 100 mg orally twice daily and metronidazole 500 mg orally twice daily, both for 14 days.

Neurosyphilis or ocular syphilis: IV aqueous penicillin GNeurosyphilis, ocular syphilis and otosyphilis: aqueous crystalline penicillin G 18–24 million units/day IV (3–4 million units every 4 hours or continuous infusion) for 10–14 days; CNS involvement can occur at any stage.

Penicillin allergy, not pregnant: doxycyclineNonpregnant penicillin-allergic patients: doxycycline 100 mg twice daily for 14 days (early syphilis) or 28 days (late latent); avoid azithromycin because of resistance; desensitize if adherence or follow-up is doubtful.

Inpatient PID: IV ceftriaxone, doxycycline, metronidazoleParenteral PID regimen: ceftriaxone 1 g IV every 24 hours plus doxycycline 100 mg every 12 hours plus metronidazole 500 mg every 12 hours; reassess if no improvement within 72 hours.

Treat sex partners from the past 60 daysEvaluate and presumptively treat sex partners from the 60 days before symptom onset or diagnosis; where legal, use expedited partner therapy (eg, cefixime 800 mg for gonorrhea partners if chlamydia is excluded).

Red flags & don'ts

Avoid harm

Jarisch-Herxheimer: fever within hours of penicillin complicationThe Jarisch-Herxheimer reaction — fever, malaise, headache, rigors and transient worsening of lesions within 6–12 hours of treating early (especially secondary) syphilis — is not a penicillin allergy.

The rules

Know these

Add doxycycline unless chlamydia is excludedWhen treating gonorrhea, also treat chlamydia with doxycycline 100 mg twice daily for 7 days unless chlamydial infection has been excluded.

Pregnant and penicillin-allergic: desensitizePregnant patients with syphilis and a penicillin allergy should be desensitized and treated with penicillin G.

Admit PID for abscess, pregnancy or severe illnessHospitalize for PID when a surgical emergency cannot be excluded, with tubo-ovarian abscess, pregnancy, severe illness, nausea and vomiting or temperature > 38.5 °C, inability to tolerate oral therapy, or no response to it.

Gonorrhea or chlamydia?

Commonly confused

First-line	Ceftriaxone 500 mg IM once
Alternatives	Gentamicin + azithromycin; cefixime 800 mg
Test of cure	Pharyngeal infection, at 7–14 days
Retest	3 months

More detail

Reference

Show 7 reference facts

Patients should abstain from sex for 7 days after single-dose therapy or until a 7-day course is complete, and until all partners are treated.

An IUD does not need to be removed when PID is diagnosed; consider removal if there is no clinical improvement within 48–72 hours of treatment.

Gonorrhea alternatives: gentamicin 240 mg IM plus azithromycin 2 g orally for cephalosporin allergy, or cefixime 800 mg orally once if ceftriaxone is unavailable (less effective for pharyngeal infection).

In December 2025 the FDA approved two oral drugs, zoliflodacin and gepotidacin, for uncomplicated urogenital gonorrhea (age ≥ 12); they are reserved for resistant infection or when ceftriaxone cannot be used.

Doxycycline postexposure prophylaxis (doxy-PEP), 200 mg once within 72 hours of condomless sex, is recommended for MSM and transgender women with syphilis, chlamydia or gonorrhea in the past 12 months.

Use only pure benzathine penicillin G (Bicillin L-A) for syphilis; the similarly named benzathine-procaine combination (Bicillin C-R) is not adequate treatment.

Syphilis serology needs both a nontreponemal (RPR or VDRL) and a treponemal test, and both can be negative for 3–6 weeks after infection, so early primary syphilis may be seronegative.

Pearl

Treat the patient, treat the partners, retest in 3 months.

Sources · CDC — Sexually Transmitted Infections Treatment Guidelines, 2021: Gonococcal Infections Among Adolescents and Adults · CDC — STI Treatment Guidelines, 2021: Chlamydial Infections · CDC — STI Treatment Guidelines, 2021: Primary and Secondary Syphilis · CDC — STI Treatment Guidelines, 2021: Latent Syphilis · CDC — STI Treatment Guidelines, 2021: Neurosyphilis, Ocular Syphilis, and Otosyphilis · CDC — STI Treatment Guidelines, 2021: Pelvic Inflammatory Disease · Merck Manual Professional — Syphilis · Bachmann LH et al. CDC Clinical Guidelines on the Use of Doxycycline Postexposure Prophylaxis for Bacterial STI Prevention, United States, 2024. MMWR Recomm Rep 2024;73(RR-2):1–8 · NYC Department of Health — Dear Colleague: New Gonorrhea Treatment Options (April 13, 2026) · FDA News Release — FDA Approves Two Oral Therapies to Treat Gonorrhea (December 12, 2025) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).