What is the first-line antibiotic choice after intercourse for suspected sexually transmitted infections (STIs)?

First-Line Antibiotic Choice After Intercourse for Suspected STIs

For suspected sexually transmitted infections after intercourse, the first-line antibiotic regimen is ceftriaxone 125 mg IM in a single dose PLUS azithromycin 1 g orally in a single dose if chlamydial infection is not ruled out. 1

Rationale for Treatment

• Dual therapy is recommended because coinfection with both gonorrhea and chlamydia is common in patients with STIs 1
• This combination targets the two most common bacterial STIs: Neisseria gonorrhoeae and Chlamydia trachomatis 1
• Single-dose therapy ensures virtually 100% compliance, which is crucial for effective treatment of STIs 2

Recommended First-Line Regimen

For suspected gonorrhea and chlamydia:

• Ceftriaxone 125 mg IM in a single dose 1
  • Highly effective against uncomplicated gonococcal infections
  • Reliable cure rate >90% for gonococcal infections 1

PLUS (if chlamydial infection is not ruled out):

• Azithromycin 1 g orally in a single dose 1
  • Equally efficacious to doxycycline for chlamydial infections 1
  • Provides single-dose, directly observed therapy 1
  • 96% cure rate for chlamydial infections 3

Alternative Regimens

If ceftriaxone is not available:

• Ciprofloxacin 500 mg orally in a single dose (for gonorrhea) 1
• Cefixime 400 mg orally plus azithromycin 1 g orally in a single dose 1

If azithromycin is not available:

• Doxycycline 100 mg orally twice daily for 7 days (for chlamydia) 1

Special Considerations

Pregnancy

• Pregnant women should not be treated with quinolones or tetracyclines 1
• Recommended regimens for pregnant women:
  • Ceftriaxone 125 mg IM for gonorrhea 1
  • Azithromycin 1 g orally in a single dose or amoxicillin 500 mg orally three times a day for 7 days for chlamydia 1

Allergy Considerations

• For patients who cannot tolerate cephalosporins or quinolones, spectinomycin can be used, but it's unreliable (only 52% effective) against pharyngeal infections 1

Adolescents

• The same regimens can be used for adolescents who weigh >45 kg 1

Follow-Up Recommendations

• Patients treated with recommended regimens do not need a test of cure 1
• Patients should be instructed to abstain from sexual intercourse until therapy is completed and until they and their sex partners no longer have symptoms 1
• Sex partners should be evaluated and treated if they had sexual contact with the patient within 60 days before onset of symptoms or diagnosis 1
• Consider retesting approximately 3 months after treatment due to high rates of reinfection 1

Prophylaxis After Sexual Assault

For cases of sexual assault, a more comprehensive regimen is recommended:

• Ceftriaxone 125 mg IM in a single dose, PLUS
• Metronidazole 2 g orally in a single dose, PLUS
• Azithromycin 1 g orally in a single dose or doxycycline 100 mg orally twice a day for 7 days 1

This approach is supported by evidence showing high acceptability (88%) of antibiotic prophylaxis among sexual assault victims and low follow-up rates (57% at two weeks, 30% at three months) 4.