Understand HSR

What is an abacavir HSR?


Abacavir is associated with a risk for hypersensitivity reactions (HSR) characterised by fever and/or rash with other symptoms indicating multi-organ involvement.

An abacavir hypersensitivity reaction (HSR) is an idiosyncratic reaction.

The approximate reporting rate of abacavir HSR in clinical trials was:

  • 1% in trials that excluded subjects testing positive for the HLA-B*5701 allele (n=1322)1
  • 5% in trials where HLA-B*5701 screening was not performed (n=8038)2

Abacavir HSR is clinically well characterised:3

  • Most HSR include fever and/or rash
  • Other symptoms include respiratory, gastrointestinal and constitutional symptoms such as lethargy and malaise.
  • Multiple symptoms are typical in most cases of hypersensitivity

Diagnosis is complicated by:4

  • Variable presentation with nonspecific symptoms
  • Concomitant use of other antiretroviral medications with overlapping adverse event profiles
  • Potential misdiagnosis of hypersensitivity as respiratory disease (pneumonia, bronchitis, pharyngitis), or gastroenteritis

Note: Symptomatology was evaluated from clinical trials where HLA B*5701 screening was not performed


1.      Calculated from published data for four Marketing Authorisation Holder clinical trials: Post F et al. JAIDS. 2010; 55(1): 49-57*,  Young B et al. AIDS. 2008; 22: 1673-1675*, Wohl DA et al. PLoS One. 2014; 9(5): e96187*,  Walmsley SL et al. N Engl J Med. 2013; 369(19): 1807-1818*

2.      Cutrell et al. Ann Pharmacother. 2004; 38: 2171-2172.*

3.      Hernandez et al. Abstract presented at: 15th International AIDS Conference; July 11-16, 2004; Bangkok, Thailand. Note: Symptomatology was evaluated from clinical trials where HLA B*5701 screening was not performed.

4.      Hetherington et al. Clin Ther. 2001; 23: 1603-1614.*

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