The longstanding rule for Glaxo Wellcome's abacavir
(Ziagen) has been that those who experience hypersensitivity (allergic
reactions) during their initial use of the drug (3 to 5 percent of users)
must stop it and never restart it, because the second go-round could
result in extreme reactions, even death. Now the company has sent a
letter to warn physicians -- and added info to its "black box" package-insert
warning -- that any reintroduction of the drug, even for those
who think they never had a reaction, must be done very carefully. The
heightened vigilance comes after reports of unexpectedly severe reactions
-- most within hours, but some days or weeks later -- in those restarting
the drug after discontinuation due to health problems thought to be
unrelated to the med.
The problem is that some of the nonspecific symptoms
of abacavir hypersensitivity may have been missed or misdiagnosed as
respiratory or gastrointestinal (GI) tract infections, allergies to
other meds, or other problems common among HIVers. Among first-timers
who have reactions, complaints include: fever (seen in 80 percent);
rash (60 to 70 percent); headache (60 percent), generally feeling bad
or low in energy (60 percent); GI problems including nausea, vomiting,
diarrhea or stomach pain (50 percent); and cough, shortness of breath
or sore throat (20 percent). Other less common symptoms include itching,
swelling, joint and body aches. Most reactions among abacavir first-timers
occur during the first six weeks on the drug, but in some cases develop
months later, so even longtime users can't be certain they're home free.
So for those thinking about reintroducing the
drug after more than a missed dose or two, any prior symptoms even remotely
suggesting a previous reaction mean an automatic thumbs-down. And suspicious
past or not, going back to abacavir should be done always with caution
and only under a doc's supervision, with quick access to emergency care.
If, after restarting the drug, any symptoms develop, don't just
stiff-upper-lip it -- get on the horn to your doc right away.