A patient developed a potentially life-threatening hypersensitivity reaction to the nucleoside analogue (NRTI) abacavir (ZiagenTM) after receiving a single dose of the drug. The case is reported in a letter in the February 20th edition of AIDS.
It is well known that a hypersensitivity reaction to abacavir occurs in approximately 5% of individuals treated with the drug. The reaction is normally progressive and occurs days or weeks after therapy with the drug is initiated. A more severe reaction can occur within hours or minutes in patients who resume treatment with abacavir after previously stopping the drug due to a hypersensitivity reaction.
In their letter to AIDS, doctors from Vancouver, Canada report a life-threatening allergic reaction to abacavir in a 45-year-old native American within minutes of receiving his first dose of the drug.
The patient was diagnosed with HIV infection in 1995 and had been an in-patient in a psychiatric hospital since 1985. The man had a history of allergic skin rash, attributed to hypersensitivity to amoxicillin.
His previous anti-HIV therapy had included AZT, ddC, 3TC, d4T and indinavir, but the man had never been treated with abacavir. In the spring of 2002, his CD4 cell count was 160 cells/mm3 and his viral load was 87,000 copies/ml, leading doctors to initiate a HAART regimen consisting of nevirapine, tenofovir, 3TC and ddI (EC). As his viral load was over 100,000 copies/ml in the autumn of 2002, this regimen was changed, and comprised Kaletra, abacavir, tenofovir and ddI (EC).
Therapy for the man’s psychiatric condition was administered at the same time.
Within half an hour of receiving his first 300mg dose of abacavir, the individual complained of dizziness, muscle pain, weakness, nausea and abdominal discomfort. Shortly after, his blood pressure fell dangerously and a rash developed on his neck, chest, face and arms. All these symptoms were consistent with the abacavir hypersensitivity reaction.
The severity of his symptoms led doctors to transfer the patient to an intensive care facility, where he was treated with intravenous dopamine and corticosteroids and antihistamines. Although he also received intravenous antibiotics, blood cultures later revealed that he did not have an infection.
Dopamine was discontinued after approximately 24 hours and after the man’s vital signs remained stable for a further 24 hours, he was discharged from intensive care.
Two weeks later, anti-HIV therapy was recommenced without incident. His regimen at this time included Kaletra, soft gel saquinavir, tenofovir and ddI (EC). A genetic test revealed that the man did not have leukocyte antigen polymorphisms associated with the abacavir hypersensitivity reaction.
The investigators recommend that, “in the absence of a reliable screening test for predicting abacavir [hypersensitivity reaction], HIV treating physicians must maintain a high index of suspicion for this syndrome even in patients taking their first dose of abacavir. Patients starting abacavir may benefit from doing so under direct observation by healthcare professionals able to implement resuscitation rapidly.”
Further information on this website
Abacavir - overview
Abacavir hypersensitivity reaction experienced by 5% say GSK investigators - news story
de la Rosa R et al. Life-threatening reaction after first ever dose of abacavir in an HIV-1-infected patients. AIDS 18: 578 – 579, 2004.