Abacavir reaction: Some 5 percent of HIVers display a hypersensitivity to the nuke abacavir (Ziagen), with symptoms including rash, abdominal pain, fever, cough or sore throat, nausea, vomiting and breathing problems. The reaction occurs in the first few weeks after starting the med and can be life-threatening, requiring immediate medical attention. Now comes news that one HIVer reacted after just one dose, reminding doctors to monitor patients very closely when they start taking Ziagen. The HIVer was treated with IV drugs in intensive care for a day, recovered and began a different HIV combo.