Tools for Practice


#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   
  • 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     
  • 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 
Context:   
  • CDC guidelines suggest PrEP (TDF+FTC) be considered if high risk of HIV infection.11   
  • 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 
August 29, 2016

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Author(s):

  • Corey Jefferies BScPharm
  • Daniel McKennitt MD MPH(c) CCFP
  • G. Michael Allan MD CCFP

1. Fonner VA, Dalglish SL, Kennedy CE, et al. AIDS. 2016; 30(12):1973-83.

2. Jiang J, Yang X, Ye L, et al. PLoS ONE. 2014; 9(2):e87674.

3. Okwundu CI, Uthman OA, Okoromah CAN. Cochrane Database Syst Rev. 2012; 7:CD007189.

4. Grant RM, Lama JR, Anderson PL, et al (iPrEx). N Engl J Med. 2010; 363:2587-99.

5. McCormack S, Dunn DT, Desai M, et al (PROUD). Lancet. 2016; 387:53-60.

6. Baeten JM, Donnell D, Ndase P, et al (Partners PrEP). N Engl J Med. 2012; 367:399-410.

7. Thigpen MC, Kebaabetswe PM, Paxton LA, et al (TDF2). N Engl J Med. 2012; 367:423-34.

8. Choopanya K, Martin M, Suntharasamai P, et al (Bangkok Tenofovir). Lancet. 2013; 381:2083-90.

9. Van Damme L, Corneli A, Ahmed K, et al (FEM-PrEP). N Engl J Med. 2012; 367:411-22.

10. Marrazzo JM, Ramjee G, Richardson BA, et al (VOICE). N Engl J Med. 2015; 372:509-18.

11. US Public Health Service. Preexposure prophylaxis for the prevention of HIV infection in the United States. CDC 2014. Available from: https://www.cdc.gov/hiv/pdf/prepguidelines2014.pdf. Last accessed July 2, 2016.

12. Gomez GB, Borquez A, Case KK, et al. PLoS Med. 2013; 10(3):e1001401.

13. Smith DK, Herbst JH, Rose CE. Sex Transm Dis. 2015; 42:88-92.

14. Volk JE, Marcus JL, Phengrasamy T, et al. Clin Infect Dis. 2015; 61:1601-3.

Authors do not have any conflicts of interest to declare.