Heads up, HIV vets: In October, the Food and Drug Administration (FDA) issued an official warning about taking tenofovir (Viread) and ddI (Videx EC) together. A recent study showed that the recommended dose (300 mg) of the nucleotide bumps up blood levels of buffered ddI and therefore the risk of ddI-related side effects, including neuropathy and liver-damaging pancreatitis and lactic acidosis. The FDA’s response? Avoid this combo!

But some HIV docs are working with this drug interaction, especially if the combo is working for the patient. Since another way of looking at it, says Johns Hopkins drug guru Charles Flexner, MD, is that Viread “may simply improve the absorption of ddI [by 60 percent],” why not just use a lower dose of ddI? The dose doctors are using is 250 mg (with Viread and with food). And you don’t-fix-it-if-it-ain’t-broke types might even want to just go with the flow—but be on the lookout for elevated levels of amylase and lipase. Consider yourself warned.