Abacavir (Adverse effects)

Abacavir is a reverse transcriptase inhibitor antiretroviral drug used in the treatment of HIV. Hypersensitivity to the drug, the main adverse effect, is associated with the presence of the HLA-B*5701 allele.

Abacavir is a drug of the antiretroviral family, indicated for the combination treatment of Human Immunodeficiency Virus or HIV infection. The drug works by preventing the HIV virus from reproducing and slows the progression of the infection.

Abacavir does not completely cure HIV infection, but it reduces the amount of virus in the body and keeps it at low levels, and it also increases the number of CD4 cells in the blood, a type of white blood cell that plays an important role in fighting infection.

Clinical guidelines do not recommend the use of abacavir in people who carry the HLA-B*5701 allele as they are more susceptible to developing hypersensitivity to abacavir, an adverse effect that can occur during the first 6 weeks of treatment and can be very serious. Therefore, before starting treatment, it is important to know whether or not the patient has this allele.

Hypersensitivity to abacavir can manifest with fever, chills, skin rash, gastrointestinal and respiratory symptoms, among others, which can be very severe.

The prevalence of the HLA-B*5701 allele is higher in Caucasian populations (5-8%) than in African-American, Asian and Hispanic populations (26-3.6%).

In addition, it should be noted that some individuals may be more susceptible to adverse effects with abacavir use, regardless of their genetics. Special care should be taken when taking abacavir if:

  • Have had previous liver disease, including hepatitis B or C.
  • Are overweight (especially women)
  • Are diabetic and use insulin
  • Have severe kidney disease
  • Take phenytoin, ribavirin, or methadone.


  • Epzicom
  • Ziagen®

Genes analyzed



Ma JD, Lee KC, Kuo GM. HLA-B*5701 testing to predict abacavir hypersensitivity. PLoS Curr. 2010 Dec 7;2:RRN1203.

Martin MA, Hoffman JM, Freimuth RR, et al. Clinical Pharmacogenetics Implementation Consortium Guidelines for HLA-B Genotype and Abacavir Dosing: 2014 update. Clin Pharmacol Ther. 2014 May;95(5):499-500.

Gilani B, Vaqar S. HLA B 5701 Testing. 2023 Jan 2. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

Small CB, Margolis DA, Shaefer MS, Ross LL. HLA-B*57:01 allele prevalence in HIV-infected North American subjects and the impact of allele testing on the incidence of abacavir-associated hypersensitivity reaction in HLA-B*57:01-negative subjects. BMC Infect Dis. 2017 Apr 11;17(1):256.

Tangamornsuksan W, Lohitnavy O, Kongkaew C, et al. Association of HLA-B*5701 genotypes and abacavir-induced hypersensitivity reaction: a systematic review and meta-analysis. J Pharm Pharm Sci. 2015;18(1):68-76.

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