Abacavir is metabolized via a nonmicrosomal pathway to its glucuronide and carboxylic acid metabolites. The currently used dose is 300 mg twice daily. Preliminary safety and activity data are available. Side effects identified include headache, asthenia, nausea, vomiting, abdominal pain, diarrhea, insomnia, fever, dizziness, and rash. The average time to onset of symptoms is about 9 days, ranging from a few days to about 1 month.
Symptoms rapidly abate with discontinued use of the drug.
However, in the few patients rechallenged with abacavir, life-threatening symptoms and even death have been reported. Therefore, abacavir therapy should be stopped if suspected hypersensitivity reactions occur, and the patient should not be rechallenged with this drug. Efavirenz was evaluated in combination with zidovudine-lamivudine. Rare cases of rash have also been noted. Amprenavir is an investigational protease inhibitor with activity against HIV in vitro.