#169 Pre-Exposure Prophylaxis (PrEP): Are you PrEP’d for the future of HIV prevention?
CLINICAL QUESTION
In patients at higher risk of contracting HIV, can daily antiviral therapy prevent infection?
BOTTOM LINE
Tenofovir/emtricitabine (PrEP) once daily reduces the risk of HIV by ~50%, preventing infection for ~1 in 50 per year. A year of therapy costs ~$12,000 and ~1 in 34 develop nausea/vomiting due to the drug.
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EVIDENCE
PrEP is tenofovir 300 mg (TDF) +/- emtricitabine 200 mg (FTC) once daily.
- Three systematic reviews1-3 with 6-15 Randomized Controlled Trials (RCTs), new HIV infection statistically significantly reduced:
- Meta-analysis (10 RCTs, 17,423 patients): 51% relative risk reduction (RRR).1
- Others2,3 similar.
- Event rates over ~1 year:2 2% PrEP versus 4% placebo, Number Needed to Treat (NNT)=50.
- Adherence matters: Adherence >70%, RRR=70% but adherence <40%, effect not significant.1
- Meta-analysis (10 RCTs, 17,423 patients): 51% relative risk reduction (RRR).1
- Seven primary RCTs (total 18,582 patients):
- High-risk groups studied: Homosexual men (two RCTs);4,5 Heterosexual couples with one HIV positive (one RCT);6 Single heterosexuals –Africa (one RCT);7 IV drug-users –Thailand (one RCT);8 Women –Africa (two RCTs).9,10
- All similar with NNT=16-67 over ~1 year,4-8 except:
- Two RCTs of African women:9,10 No effect but adherence very low.
- Example: ≤30% had drug in serum when tested.10
- High-risk groups studied: Homosexual men (two RCTs);4,5 Heterosexual couples with one HIV positive (one RCT);6 Single heterosexuals –Africa (one RCT);7 IV drug-users –Thailand (one RCT);8 Women –Africa (two RCTs).9,10
- Other aspects:
- Condom use ~80% and generally similar between groups.4,6,7,10
- TDF effect likely similar to TDF+FTC,1 but TDF+FTC most studied.
- Adverse effects: Generally increased nausea/vomiting3 (example 8% versus 5%, NNH=34).8
- Serious adverse events not increased.4-10
- CDC guidelines suggest PrEP (TDF+FTC) be considered if high risk of HIV infection.11
- Before starting PrEp, check renal function, hepatitis B, pregnancy, and (if at risk) osteoporosis.
- Monitor renal function and for HIV (stop if positive).
- Resources available http://www.catie.ca/en/prevention/statements/prep.
- Although cost is $12,000/year, PrEP can be cost effective.12
- Modeling study: Homosexual men contracting HIV annually:13
- 10.9% if no PrEP or condom use.
- ~3% if excellent PrEP or condom adherence.
- 0.9% if excellent PrEP and condom adherence.
- Unclear if PrEp increases risk behaviour:
- Most research suggests not,1 but one RCT found more PrEP users had multiple partners without condoms (21% versus 12%)5 and cohort study found 41% of men used condoms less.14
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