The Pharmaceutical Journal Vol 264 No 7084 p284
February 19, 2000 Clinical

New caution on abacavir hypersensitivity

Patients taking Glaxo Wellcome's anti-HIV drug abacavir must be informed about the symptoms that could indicate a hypersensitivity reaction, says the Committee on Safety of Medicines. It says that hypersensitivity reactions to the drug can be serious and, rarely, fatal. In some cases, reactions have presented as respiratory symptoms.
Abacavir (Ziagen) was launched in July, 1999, with a warning that hypersensitivity had been reported in around 3 per cent of patients. Glaxo Wellcome said at the time that patients with a diagnosed hypersensitivity reaction should discontinue treatment and abacavir must never be restarted.
The CSM says that, while abacavir remains a useful drug, the manufacturer has identified a number of hypersensitivity reactions that presented as upper respiratory tract symptoms of sore throat, 'flu-like illness, cough and breathlessness. Delayed diagnosis or re-exposure to abacavir has resulted in very severe reactions within a few hours. "Prescribers and patients need to be aware of the different patterns of symptoms that may be the manifestation of a hypersensitivity reaction," it says.
In a statement on the matter, the European Medicines Evaluation Agency (EMEA) says that nearly all patients with hypersensitivity reactions to abacavir have fever or rash. These reactions usually occur within the first six weeks of treatment. Respiratory symptoms have been part of the reaction in around 20 per cent of patients with hypersensitivity and may initially include dyspnoea, pharyngitis or cough. Deaths have occurred among patients initially thought to have acute respiratory diseases who were only later recognised to have had a hypersensitivity reaction. In cases with a fatal outcome, respiratory symptoms were present in around 80 per cent of cases.
Glaxo Wellcome says that 11 deaths possibly related to hypersensitivity (none in the UK) had been reported by January, 2000.