What post‑exposure prophylaxis medications are recommended for a patient after exposure to HIV, hepatitis B, and common bacterial sexually transmitted infections?

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Last updated: October 12, 2026 • View editorial policy

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Post-Exposure Prophylaxis for STD Exposure

For patients exposed to STDs, immediately initiate HIV post-exposure prophylaxis (PEP) within 72 hours if HIV exposure occurred, provide hepatitis B vaccination/immunoglobulin based on vaccination status, and consider doxycycline 200 mg as a single dose within 72 hours for bacterial STI prevention in men who have sex with men (MSM) and transgender women.

HIV Post-Exposure Prophylaxis

Start HIV PEP within 72 hours of exposure using a basic two-drug regimen 1:

Basic Regimen (First-line)

  • Zidovudine (AZT) 600 mg daily (divided into 2-3 doses) + Lamivudine (3TC) 150 mg twice daily
  • Available as single combination tablet (Combivir) for improved adherence
  • Continue for 4 weeks total
  • Monitor for drug toxicity within 72 hours of starting and at 2 weeks 1

Alternative Regimens

If the basic regimen is contraindicated or source virus resistance is suspected:

  • Lamivudine 150 mg twice daily + Stavudine 40 mg twice daily (30 mg if <60 kg)
  • Consider expanded 3-drug regimen with addition of protease inhibitor (Indinavir or Nelfinavir) for high-risk exposures 1

HIV Follow-up Testing

  • Baseline, 6 weeks, 3 months, and 6 months post-exposure 1
  • Test immediately if acute retroviral syndrome symptoms develop

Hepatitis B Post-Exposure Prophylaxis

Management depends on the exposed person's vaccination status 1:

For Unvaccinated Individuals

  • Initiate hepatitis B vaccine series immediately
  • Add HBIG (Hepatitis B Immune Globulin) if source is HBsAg-positive
  • Test for anti-HBs response 1-2 months after completing vaccine series

For Previously Vaccinated with Known Response

  • No treatment needed if adequate anti-HBs titer documented

Follow-up

  • Anti-HBs testing 1-2 months after last vaccine dose (cannot assess if HBIG given within 3-4 months) 1

Hepatitis C Post-Exposure Management

No post-exposure prophylaxis is recommended for hepatitis C 1.

Monitoring Strategy

  • Baseline anti-HCV and ALT testing
  • Repeat at 4-6 months post-exposure
  • Consider HCV RNA at 4-6 weeks if earlier diagnosis desired 1

Bacterial STI Post-Exposure Prophylaxis (Doxycycline PEP)

For MSM and transgender women with recent bacterial STI history, prescribe doxycycline 200 mg as a single dose to be taken within 72 hours after oral, vaginal, or anal sex 2.

Eligibility (Strong Evidence)

  • Men who have sex with men (MSM)
  • Transgender women
  • Must have had a bacterial STI diagnosed in the previous 12 months 2

Dosing Instructions

  • 200 mg single dose (any doxycycline formulation)
  • Take as soon as possible within 72 hours after sexual exposure
  • Maximum 200 mg per 24-hour period 2
  • Take with full stomach and full glass of liquid
  • Remain upright for 1 hour after taking to prevent esophagitis

Important Counseling Points

  • Separate dose by at least 2 hours from dairy products, antacids, calcium, iron, magnesium, or sodium bicarbonate 2
  • Photosensitivity risk—use sun protection
  • Does not interact with gender-affirming hormones 2

Reassessment

  • Evaluate ongoing need every 3-6 months 2
  • Prescribe sufficient doses based on anticipated sexual activity until next visit

Evidence Strength

Recent real-world data shows doxycycline PEP reduces chlamydia by 79% (RR 0.21), syphilis by 80% (RR 0.20), and urethral/rectal gonorrhea modestly (RR 0.88 overall) 3. Clinical trials demonstrate 71% reduction in all bacterial STIs when prescribed broadly 4.

Populations Without Current Recommendation

No recommendation can be made at this time for doxycycline PEP in:

  • Cisgender women
  • Cisgender heterosexual men
  • Transgender men
  • Other queer and nonbinary persons 2

Evidence is insufficient to assess benefits versus harms in these populations.

Comprehensive Sexual Health Approach

When providing any STD post-exposure prophylaxis:

Immediate Testing

  • NAAT testing for gonorrhea and chlamydia at all exposed anatomic sites (pharyngeal, rectal, urethral/vaginal)
  • Serologic syphilis testing 2
  • Treat any identified infections immediately

Risk Reduction Counseling

  • Condom use discussion
  • Consider reducing number of partners
  • Link to HIV PrEP if HIV-negative and not already using 2

Vaccination Status

  • Ensure hepatitis A and B vaccination complete
  • HPV vaccination if age-appropriate

Critical Timing Considerations

All post-exposure prophylaxis is time-sensitive:

  • HIV PEP: Must start within 72 hours (sooner is better) 1
  • Doxycycline PEP: Most effective within 72 hours 2
  • Hepatitis B: Vaccine/HBIG should be given as soon as possible 1

Common Pitfalls to Avoid

  1. Don't delay HIV PEP while awaiting source patient testing—start empirically if high-risk exposure
  2. Don't prescribe doxycycline PEP to populations without evidence (cisgender women, heterosexual men) 2
  3. Don't exceed 200 mg doxycycline per 24 hours even with multiple sexual encounters 2
  4. Don't assume prior hepatitis B vaccination equals immunity—verify anti-HBs titers 1
  5. Don't give prophylactic treatment for hepatitis C—only monitor and treat if infection develops 1

References

4
Research

Potential impact of doxycycline post-exposure prophylaxis prescribing strategies on incidence of bacterial sexually transmitted infections.

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2023

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.