Symptoms, Side Effects and Adherence in the iPrEx Open-Label Extension

Clin Infect Dis. 2016 May 1;62(9):1172-7. doi: 10.1093/cid/ciw022. Epub 2016 Jan 20.


Background: Blinded clinical trials have reported a modest and transient "start-up syndrome" with initiation of tenofovir-based pre-exposure prophylaxis (PrEP). We evaluate this phenomenon and its effect on adherence in an open-label PrEP study.

Methods: In the iPrEx open-label extension (OLE) study, an 18-month open-label, multi-site PrEP cohort taking daily oral co-formulated tenofovir/emtricitabine, we examined the prevalence and duration of PrEP-associated symptoms and their effect on adherence, assessed by drug levels in dried blood spots tested monthly for the first 3 months.

Results: Symptom reports peaked within the first month, with 39% reporting potentially PrEP-related symptoms compared to 22% at baseline. Symptoms largely resolved to pre-PrEP levels by 3 months.Symptoms varied substantially in frequency by study site (range in 1-month symptoms: 11% to 70%). Nongastrointestinal (GI) symptoms were not associated with adherence (odds ratio [OR] = 1.2, 95% confidence interval [CI], .4-3.7); however, GI-associated symptoms in the first 4 weeks were inversely associated with adherence at 4 weeks (OR = 0.47, 95% CI, .23-.96). Reports of GI symptoms were associated with 7% (95% CI, 4%-11%) of suboptimal adherence in this cohort.

Conclusions: PrEP-associated symptoms in the open-label setting occur in a minority of users and largely resolve within 3 months. GI symptoms are associated with a modest reduction in PrEP adherence, but good adherence is possible even in the presence of frequent symptom reports.

Clinical trials registration: Clinicaltrials.govNCT00458393.

Keywords: HIV prevention; PrEP; pre-exposure prophylaxis; tenofovir/emtricitabine.

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-HIV Agents / adverse effects*
  • Emtricitabine / adverse effects*
  • HIV Infections / prevention & control*
  • Humans
  • Male
  • Medication Adherence*
  • Pre-Exposure Prophylaxis*
  • Tenofovir / adverse effects*


  • Anti-HIV Agents
  • Tenofovir
  • Emtricitabine

Associated data