What is prophylactic medication for concerns about sexually transmitted diseases (STDs)?

Prophylactic Medications for Sexually Transmitted Diseases (STDs)

For individuals concerned about STD exposure, doxycycline post-exposure prophylaxis (doxy PEP) is recommended for high-risk populations, while a combination regimen of ceftriaxone, metronidazole, and azithromycin/doxycycline is recommended after sexual assault.

Post-Exposure Prophylaxis After Sexual Assault

For individuals who have experienced sexual assault, prophylactic treatment is strongly recommended due to the difficulty in ensuring follow-up and the psychological reassurance it provides 1.

Recommended Regimen After Sexual Assault:

• 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 empiric regimen covers chlamydia, gonorrhea, trichomoniasis, and bacterial vaginosis. Additionally, hepatitis B vaccination should be administered at the initial examination, with follow-up doses at 1-2 and 4-6 months 1.

Doxycycline Post-Exposure Prophylaxis (Doxy PEP)

The CDC recently (2024) recommended doxycycline post-exposure prophylaxis (doxy PEP) as a novel approach for preventing bacterial STIs in specific high-risk populations 1, 2.

Eligibility for Doxy PEP:

• Men who have sex with men (MSM)
• Transgender women (TGW)
• Individuals who have had at least one bacterial STI diagnosed in the past 12 months 1, 2

Doxy PEP Administration:

• Dose: 200 mg of doxycycline
• Timing: Within 72 hours after sexual exposure
• Maximum: 200 mg per 24-hour period 2

Efficacy of Doxy PEP:

• Reduces syphilis and chlamydia infections by >70%
• Reduces gonococcal infections by approximately 50% 1, 2

Important Considerations and Limitations

For Sexual Assault Prophylaxis:

• The efficacy of the recommended regimens in preventing STIs after sexual assault has not been formally evaluated 1
• Patients should be counseled about possible gastrointestinal side effects with the combination regimen 1
• Follow-up examinations are recommended at 2 weeks after the assault, with serologic tests for syphilis and HIV repeated at 6,12, and 24 weeks if initial results were negative 1

For Doxy PEP:

• Not currently recommended for cisgender women, as a 2023 randomized controlled trial showed no significant reduction in STI incidence (relative risk 0.88; 95% CI 0.60-1.29) 3
• Not recommended for cisgender heterosexual men, transgender men, and other queer and nonbinary persons due to insufficient evidence 2
• Should be taken with food or milk and a full glass of water
• Patient should remain upright for at least 1 hour after taking to prevent esophageal irritation 2
• Potential side effects include photosensitivity, esophagitis, and gastrointestinal intolerance 2

Monitoring and Follow-Up

• For doxy PEP users: Baseline STI testing at initiation and regular screening every 3-6 months 2
• Ongoing need for doxy PEP should be reassessed every 3-6 months 1, 2
• For those not known to be HIV-positive: HIV screening every 3-6 months 2

Comprehensive Approach

Prophylactic medication should be implemented as part of a comprehensive sexual health approach, including:

• Risk reduction counseling
• Regular STI screening and treatment
• Recommended vaccinations (hepatitis B, HPV)
• HIV PrEP or treatment as appropriate 1, 2
• Condoms and vaginal spermicides can also reduce the risk of certain STDs 4

Prophylactic medications should not be used as a replacement for other STI prevention strategies but rather as part of a multi-layered approach to sexual health.