What prophylactic medications are recommended after unprotected sex with a partner of unknown Sexually Transmitted Infection (STI) history in Canada?

Post-Exposure Prophylaxis After Unprotected Sex with Partner of Unknown STI Status in Canada

After unprotected sex with a partner of unknown STI status, immediate STI screening and consideration of HIV post-exposure prophylaxis (nPEP) is recommended, particularly if the exposure occurred within the last 72 hours. 1

Initial Assessment

• Evaluate the exposure risk based on type of sexual contact and potential risk factors of the partner 1
• Substantial risk for HIV exposure includes contact of vagina, rectum, mouth, or other mucous membranes with blood, semen, vaginal secretions, or rectal secretions 1
• Time since exposure is critical - HIV post-exposure prophylaxis (nPEP) should be considered if within 72 hours 1

Recommended Prophylactic Interventions

HIV Prevention

• For exposures within 72 hours with substantial risk:
  • HIV nPEP should be considered on a case-by-case basis, especially if the source is known or suspected to be HIV-positive 1
  • If started, nPEP medication should be provided to last until follow-up visit (3-7 days) 1
  • Baseline CBC and serum chemistry should be performed if nPEP is initiated 1

Bacterial STI Prevention

• Empiric treatment for common bacterial STIs may be considered based on risk assessment:
  • For gonorrhea: Ceftriaxone (dosage based on body weight) as monotherapy 2
  • For chlamydia: Doxycycline is the preferred treatment 2
  • For syphilis exposure with high risk: Penicillin G benzathine 2.4 million units IM single dose 2

Follow-up Testing

• HIV antibody testing at baseline, 6 weeks, 3 months, and 6 months post-exposure 1
• Comprehensive STI screening:
  • Syphilis serologic testing (nontreponemal and treponemal tests) 1
  • Gonorrhea and chlamydia testing (urine NAAT for men; vaginal swab preferred for women) 1
  • For those reporting receptive anal sex: rectal testing for gonorrhea and chlamydia 1
  • For those reporting receptive oral sex: pharyngeal testing for gonorrhea 1
  • Consider HSV-2 serologic testing 1
  • For women: trichomoniasis testing (vaginal swab NAAT preferred) 1

Risk Reduction Counseling

• Abstain from sexual activity until test results are available and any necessary treatment is completed 1
• If sexual activity occurs before results or during treatment, use condoms consistently and correctly 1
• Both partners should get tested for STIs, including HIV, before resuming unprotected sexual intercourse 1

Important Considerations and Caveats

• The effectiveness of post-exposure prophylaxis decreases with time - seeking care as soon as possible after exposure is critical 1
• Condoms, while effective in preventing many STIs when used consistently and correctly, may not provide complete protection against all STIs, particularly those transmitted by skin-to-skin contact 1
• Even experienced condom users face some risk of STI transmission during treatment periods for acute bacterial STIs 3
• Regular STI screening is recommended for sexually active individuals, especially those with multiple partners or other risk factors 1

Follow-up Care

• Repeat STI screening is recommended 2-4 weeks after exposure, regardless of whether prophylactic treatment was provided 4
• Annual screening is recommended for all sexually active individuals, with more frequent screening (every 3-6 months) for those with ongoing risk factors 1
• Risk factors warranting more frequent screening include multiple partners, anonymous partners, substance use (especially methamphetamine), and unprotected sex outside a mutually monogamous relationship 1