Post-exposure prophylaxis for HIV

Background

• Can be sexual or non-sexual; consensual or non-consensual; and heterosexual or homosexual

Management

Risk Assessment

• If the source person is available and consents to testing, this can be done to more accurately risk stratify the exposure

Risk of HIV-positive source

Risk	Examples
substantial	HIV-positive with detectable viral load
	HIV status unknown, but from a population with high prevalence such as MSM or PWID
low but nonzero	HIV positive and believed to have undetectable viral load, with concomitant STI at time of exposure
negligible or none	confirmed HIV negative
	HIV positive with confirmed viral load <40 copies/mL without known STI at time of exposure
	HIV status unknown, in the general population

Risk of HIV transmission per act by exposure type from an HIV-positive source

Risk	Exposure	Estimated risk per act %
Very high	Transfusion	92.5
High	Anal (receptive)	1.38
	Needle sharing	0.63
Moderate	Anal (insertive)	0.11
	Vaginal (receptive)	0.08
	Vaginal (insertive)	0.04
Low	Oral sex (giving)	—
	Oral sex (receiving)	—
	Oral-anal contact	—
	Sharing sex toys	—
	Blood on compromised skin	—

Risk of HIV-Positive Source	Risk From Exposure	Action
substantial	low	PEP not required
	moderate or high	initiate PEP
low	low	PEP not required
	moderate or high	consider PEP
negligible or none	low	PEP not required
	moderate or high	PEP not required

Antiretroviral Therapy

• Screen for sexual assault, counsel about safe sex
• Screen for pregnancy and get baseline investigations (below)
• Start antiretroviral therapy within 72 hours and continue for 28 days
  • First-line: tenofovir disoproxil fumarate/emtricitabine 300 mg/200 mg PO daily plus raltegravir 400 PO bid
  • Alternative: tenofovir disoproxil fumarate/emtricitabine 300 mg/200 mg PO daily plus dolutegravir 50 mg PO daily
  • Alternative: tenofovir disoproxil fumarate/emtricitabine 300 mg/200 mg PO daily plus darunavir/ritonavir 800 mg/100 mg PO daily
• Don't forget screening for hepatitis A, hepatitis B, hepatitis C, gonorrhea, chlamydia, and syphilis

Investigations

Investigation	Baseline	Week 12	Notes
CBC	X
ALT	X		repeat at 2 weeks if abnormal
creatinine	X		repeat at 2 weeks if abnormal
hepatitis A serology	X
hepatitis B serology	X		includes HBsAb, HBsAg, and HBcAb
pregnancy test	X
HIV serology	X	X	repeat at 6 months if hepatitis C seroconversion
hepatitis C serology	X	X
gonorrhea and chlamydia	X	X	urine, throat, and rectum, depending on reported sexual activity
syphilis serology	X	X

Follow-Up

• Initial visit; follow-up at 4-6 weeks; then repeat bloodwork at 12 weeks to 4 months
• Take advantage of the opportunity to counsel patients on STIs, substance use, etc.

Further Reading

• Canadian guideline on HIV pre-exposure prophylaxis and nonoccupational postexposure prophylaxis. CMAJ. 2017;189(47):e1448-e1458. doi: 10.1503/cmaj.170494