• Lack of Interaction Between Stavudine Extended-Release Formulation (d4T XR) and Tenofovir Disoproxil Fumarate (TDF) (Poster 534)
  Authored by S. Kaul, K. Bassi, B. Damle, R. Smith, J. Gale, E. O'Mara, U. Chaudhari, K. Ryan
  View the original abstract

It is clear that the pharmaceutical industry recognizes the interest in once-daily treatment options from both people with HIV, as well as clinicians providing care. While not a mandatory feature in creating successful combinations, an increasing number of antivirals can be dosed once daily.

Since there are many ways to create successful combinations, it is important to verify the compatibility of each of the potentially interesting combinations. In general, medications in the nucleoside family do not have drug-drug interactions. However, a recent experience showing important interactions between ddI (didanosine, Videx) and tenofovir (TDF, Viread) has led to a reminder to not simply assume that there is no interaction, but to verify if this is the case between other combinations.

In this study, the researchers reviewed the drug levels to see how well we can combine the drug TDF with the new formulation of d4T (stavudine, Zerit), recently approved by the FDA as a once-daily slow-release encapsulation.

Researchers enrolled 18 people, all men, who took this combination for about nine days. They measured both blood and urine samples to ensure they had the information needed. They found absolutely no impact of TDF on d4T levels when both are taken with a "light meal" -- which is how TDF is supposed to be taken. The analysis of the levels on TDF were not yet available, however. It was also noted that, as expected, this combination was well tolerated. Only two of the 18 people reported mild nausea, body aches, and fatigue.

These data are part of what is needed to reassure us we can safely use d4T "XR" along with TDF. There is little expected interaction in the reverse direction, and while we wait for these data, clinicians can rely on past experiences that are reassuring on the lack of anticipated interactions.