OBJECTIVE: To review the clinical features, risk factors, diagnosis, and management of abacavir hypersensitivity reaction (HSR).

DATA SOURCES: A MEDLINE (1950-October 2007) and EMBASE (1980-October 2007) search using key words abacavir, HIV, human immunodeficiency virus, hypersensitivity reaction, HLA-B*5701, and patch tests was conducted. Conference abstracts and article bibliographies were reviewed to identify relevant studies.

STUDY SELECTION AND DATA EXTRACTION: Studies that investigated the clinical and immunogenetic risk factors for abacavir hypersensitivity and the benefit of genetic screening, as well as articles that focused on the clinical presentation, assessment, and management of abacavir HSR, were considered for this review.

DATA SYNTHESIS: Abacavir hypersensitivity is an immune-mediated reaction that typically occurs within the first 6 weeks of therapy. Signs and symptoms of abacavir HSR are nonspecific, which makes the diagnosis challenging, particularly in medically complex patients. Patch testing may improve the diagnosis and confirmation of abacavir HSR, but it remains experimental. Clinical management is aimed at supportive therapy and discontinuation of abacavir. Rechallenge with abacavir is contraindicated due to the risk of precipitating a lifethreatening reaction. Appropriate patient education and a clear communication plan are essential for the safe use of this medication. Identification of patients at risk of developing abacavir hypersensitivity through routine genetic screening for human leukocyte antigen (HLA) HLA-B**5701 represents a significant advance in the field of pharmacogenomics, with an apparent 100% negative predictive value when used to screen for abacavir HSR. Preliminary data suggest that pharmacogenetic testing for HLA-B*5701 is cost effective. However, until routine testing is available, pharmacovigilance is necessary for the safe and effective use of abacavir.

CONCLUSIONS: Serious adverse events associated with the use of abacavir can be avoided by appropriate recognition and management of the HSR. Screening patients for HLA-B*5701 prior to initiation of abacavir represents a tool to further decrease the risk of HSRs as well as unnecessary discontinuation of this drug.

Key Words: abacavir, HIV, drug hypersensitivity, HLA-B*5701.

Ann Pharmacother 2008;42:387-96.
Published Online, 26 Feb 2008, www.theannals.com, DOI 10.1345/aph.1K522