Norvir (ritonavir, a protease inhibitor/PI): People who take 400 mg or more of Norvir twice a day may develop a problem with the electrical charge that governs heartbeats. Caution is advised—especially for people with other heart problems. This warning doesn't apply to the low booster doses of Norvir (100 or 200 mg) used with many other PIs.

Isentress (raltegravir, an integrase inhibitor): Four men who switched to HIV combos that included Isentress experienced a serious worsening of already-existing depression. Higher doses of depression meds eased the problem within two months, and the men were able to keep taking Isentress.

Reyataz (atazanavir, a PI): Viramune (nevirapine, a non-nuke) can lower blood levels of Reyataz, so don't take the two together—even if the PI is boosted with Norvir. Reyataz can still be taken with the non-nuke efavirenz (in Sustiva and Atripla), but in that case Reyataz should be taken at 400 mg and boosted with Norvir. And you can now take Reyataz and one of the stomach-acid reducers called H2-receptor antagonists—Pepcid, for example—as long as you take the Reyataz at least two hours before or 10 hours after the stomach med.