A trend among drug companies is to market already-approved anti-HIV drugs in adherence-friendlier formulations, a welcome advance (pardon the pun) for med-weary HIVers. On the heels of Combivir, Glaxo Wellcome's first combo (AZT and 3TC) comes Trizivir, which was approved last November and adds abacavir (Ziagen) to that mix. The one-pill-twice-daily triple-nuke regimen appears to be a good bet for those hoping to avoid more complicated cocktails containing PIs and non-nukes. But for some HIVers, it may be too good to be true.

Trizivir isn't a new drug. AZT and 3TC have long been the backbone of numerous drug regimens, and abacavir -- the most potent nuke -- was approved in late 1998. When all three drugs were studied together in a clinical trial, the result was a pleasant surprise for Glaxo: Its proprietary regimen was as effective as a PI-based regimen in reducing viral load among 562 first-time treatment takers.

But there's a catch: A closer look at the trial showed that the PI indinavir (Crixivan), combined with AZT and 3TC, was more effective than Trizivir in keeping the virus undetectable in folks with viral loads in the six-digit range. "Trizivir alone isn't a good choice for individuals with viral loads above 100,000 copies," says Paul Simmons, RN, ACRN, director of treatment education and advocacy at Houston's Center for AIDS. "But Trizivir -- or any of the drugs it contains -- can be used with PIs or non-nukes to maximize its benefits."

Upon approval, the FDA warned that Trizivir could be dangerous for HIVers allergic to abacavir, a potentially serious problem in 5 percent of takers. Fever and rash are two signs that the drug should be stopped. Also, anyone who's discontinued abacavir because of side effects shouldn't try Trizivir.