We still need to be vigilant about the possibility of an allergic reaction after starting abacavir (Ziagen) even if the HLA-B*5701 screening test is negative, emphasise investigators in separate reports in the July 31st edition of AIDS.
It is now well known that abacavir can cause a severe allergic reaction in about 8% of patients. Symptoms include rash, fever, stomach or chest problems. Most cases occur within six weeks of starting treatment with the drug.
Research has found an association between hypersensitivity to abacavir and the presence of the HLA-B*5701 gene. This gene is most common among, but not limited to, individuals with a northern European racial origin.
It is possible to test patients for the presence of this gene, and only patients with a confirmed negative result should start treatment with abacavir. But doctors in London provided care to a patient who developed an usual hypersensitive reaction to abacavir, despite being HLA-B*5701-negative.
http://www.aidsmap.org/en/news/6BC68151-557F-4DE9-9562-847548A22D6A.asp