HIV Post-Exposure Prophylaxis Guidelines

Introduction to PEP Regimens

• The CDC recommends bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) as the first-line PEP regimen, due to its superior renal and bone safety compared to older regimens 1, 2, 3
• The American College of Physicians and the CDC suggest initiating PEP as soon as possible, ideally within 24 hours of exposure, with a maximum window of 72 hours 1, 2, 3

Preferred and Alternative Regimens

• The CDC recommends BIC/FTC/TAF (bictegravir 50mg/emtricitabine 200mg/tenofovir alafenamide 25mg) as the first-line PEP regimen, with dolutegravir (DTG) 50mg once daily PLUS emtricitabine/tenofovir alafenamide (FTC/TAF) 200mg/25mg once daily for 28 days as an alternative 1, 2, 3
• Tenofovir disoproxil fumarate (TDF) 300mg can be substituted for TAF if TAF is unavailable, though TAF is preferred due to better renal safety 1, 2

Critical Timing Requirements

• The CDC and other health organizations emphasize that efficacy decreases dramatically with each passing hour, and the first dose should not be delayed for any reason 1, 2, 3
• Initiate PEP as soon as possible, ideally within 24 hours of exposure, with a maximum window of 72 hours 1, 3

Baseline Assessment and Follow-Up

• Perform rapid or laboratory-based HIV antigen/antibody combination test, and add HIV nucleic acid test (NAT) if the patient received long-acting injectable PrEP in the past 12 months 1, 2, 3
• Assess for medical comorbidities, allergies, and potential drug interactions with concurrent medications 1, 2, 3

Duration and Adherence

• Complete the full 28-day course regardless of subsequent information about the source patient, as incomplete adherence significantly reduces effectiveness 1, 2, 3
• The single-tablet BIC/FTC/TAF regimen improves completion rates compared to multi-pill regimens 1

Special Populations

• For patients with impaired renal function, use tenofovir alafenamide (TAF) instead of tenofovir disoproxil fumarate (TDF) due to improved renal and bone safety profiles 1, 2, 3
• Pregnancy does not preclude the use of optimal PEP regimens and should not be a reason to deny PEP, with expert consultation advised for pregnant patients 2

Follow-Up Testing Schedule

• Within 72 hours after starting PEP: clinical evaluation and assessment for drug toxicity 1, 2, 3
• At 4-6 weeks: HIV antigen/antibody test PLUS HIV nucleic acid test (NAT) 1, 2, 3
• At 12 weeks: laboratory-based HIV antigen/antibody combination immunoassay AND HIV nucleic acid test (NAT) 1, 2, 3

Counseling Requirements

• Advise the exposed person to use precautions to prevent secondary transmission during the follow-up period 2, 3
• Instruct the patient to seek immediate medical evaluation for any acute illness during follow-up, as this may indicate acute retroviral syndrome 4, 2

Transition to PrEP After Completing PEP

• Consider immediate transition from PEP to PrEP for persons with anticipated repeat or ongoing HIV exposures 1, 3
• Perform HIV testing at completion of the 28-day PEP course before transitioning to PrEP 1, 3

HIV Post-Exposure Prophylaxis Guidelines

Immediate Assessment and PEP Initiation

• The American Academy of Family Physicians recommends performing a rapid HIV antibody or antigen-antibody combination test on the exposed person immediately to rule out pre-existing infection, and testing the source person using a fourth-generation HIV antigen-antibody test when possible 5
• The American Academy of Family Physicians and the Infectious Diseases Society of America recommend not delaying PEP initiation while waiting for test results, assuming the exposed person is HIV-negative and starting treatment immediately 5, 6
• The Infectious Diseases Society of America recommends testing for exposures to potentially infectious fluids, including cerebrospinal, amniotic, peritoneal, synovial, pericardial, or pleural fluids, via mucous membrane or parenteral routes 7

Exposures Warranting PEP

• The Infectious Diseases Society of America indicates PEP is warranted for exposures to potentially infectious fluids, including semen, vaginal secretions, rectal secretions, and breast milk, although specific details on these fluids are not provided in the cited references 6, 7

Exposures NOT Requiring PEP

• The Infectious Diseases Society of America recommends not initiating PEP when the exposed person is already HIV-positive or the source is confirmed HIV-negative, and when exposure involves non-infectious fluids such as tears, non-bloody saliva, urine, feces, vomitus, sputum, nasal secretions, and sweat 5, 6, 7, 8

Additional Testing and Interventions

• The American Academy of Family Physicians recommends testing for other sexually transmitted infections at baseline 5

Common Pitfalls to Avoid

• The American Academy of Family Physicians and the Infectious Diseases Society of America recommend never delaying PEP for source testing or risk assessment, and not using two-drug regimens unless three-drug options are absolutely unavailable 5, 6, 7

Duration of HIV Post-Exposure Prophylaxis (PEP)

Critical Treatment Duration

• The Centers for Disease Control and Prevention recommends that PEP must be continued for exactly 28 days from initiation, with no option for early discontinuation, as part of a good practice statement and existing recommendation that applies universally to all PEP regimens 9, 10, 11, 12
• The patient must complete a full 28-day course of antiretroviral therapy, regardless of exposure severity or any subsequent information about the source patient, as a critical aspect of PEP success 9

Adherence Support Throughout the 28 Days

• The Centers for Disease Control and Prevention suggests providing anti-emetics or other supportive medications proactively to manage side effects like nausea and fatigue, and scheduling follow-up visits or phone check-ins during the 28-day course to encourage adherence and address emerging side effects 10

Follow-Up Testing Schedule After the 28-Day Course

• The Centers for Disease Control and Prevention recommends testing immediately if acute retroviral symptoms develop, regardless of timeline 10

CDC Guidelines on HIV Post‑Exposure Prophylaxis (2025)

Effectiveness and Timing

• PEP is highly effective at preventing HIV infection when started within 72 hours of exposure; the strongest evidence supports a 28‑day, three‑drug regimen initiated ideally within 24 hours. (Evidence level: high‑quality observational data) 13
• Animal‑model studies demonstrate that prompt initiation of antiretroviral therapy after exposure prevents HIV transmission. (Evidence level: pre‑clinical) 14
• Observational human cohorts report extremely low HIV seroconversion rates when PEP is used according to recommendations. (Evidence level: observational) 15
• Mother‑to‑child transmission studies show that prophylactic antiretrovirals can prevent HIV transmission in the perinatal setting. (Evidence level: clinical study) 16
• Maximum benefit is achieved when the first dose is taken within 24 hours of exposure; efficacy declines sharply with each additional hour of delay. (Evidence level: observational/animal) [13][14]17
• PEP should not be initiated later than 72 hours after exposure; beyond this window it is generally not recommended. (Evidence level: animal and human data) [13][18]16

Recommended Regimen and Duration

• First‑line regimen (2025 CDC): bictegravir / emtricitabine / tenofovir alafenamide (BIC/FTC/TAF) as a single‑tablet daily dose. (Guideline recommendation) 13
• Alternative regimen (CDC): dolutegravir plus tenofovir (TAF or TDF) plus emtricitabine or lamivudine. (Guideline recommendation) 13
• WHO 2015 guidance (now superseded) recommended TDF + 3TC (or FTC) with a protease‑inhibitor (LPV/r or ATV/r) as the third drug. (Historical guideline) [18][16]
• PEP must be continued for exactly 28 days from initiation; early discontinuation is not advised. (Guideline recommendation) [13][16]14
• The 28‑day duration is based on animal‑model data and represents the current standard of care. (Evidence level: pre‑clinical) [14][17]

Follow‑Up Testing Schedule

• Baseline testing: rapid or laboratory HIV antigen/antibody combination test performed immediately; add HIV nucleic‑acid testing (NAT) if the patient received long‑acting injectable PrEP in the prior 12 months. (CDC testing algorithm) 13
• Interim testing at 4–6 weeks: laboratory‑based HIV Ag/Ab test plus diagnostic HIV NAT. (CDC testing algorithm) 13
• Interim testing may be deferred when PEP was started within 24 hours and no doses were missed. (CDC testing algorithm) 13
• Final testing at 12 weeks: laboratory HIV Ag/Ab combination immunoassay and diagnostic HIV NAT. (CDC testing algorithm) 13

Clinical Practice Considerations

• Three‑drug regimens are standard; two‑drug regimens should only be used when three‑drug options are absolutely unavailable. (Evidence level: clinical guidance) [18][16]
• Do not stop PEP early, even if the source later tests HIV‑negative or the patient experiences mild side effects; provide anti‑emetics and supportive care as needed. (Guideline recommendation) 13
• Do not prescribe PEP to individuals already living with HIV or when the source is confirmed HIV‑negative, as prophylaxis provides no benefit. (Guideline recommendation) 18
• Assess for drug‑drug interactions before selecting a regimen, as concomitant medications may influence choice. (CDC recommendation) 13

Transition to Pre‑Exposure Prophylaxis (PrEP)

• Consider immediate transition from PEP to PrEP for persons anticipating repeat or ongoing HIV exposures; perform HIV testing at completion of the 28‑day PEP course before initiating PrEP. (CDC recommendation) 13