One of the most widely used antiretroviral drugs — tenofovir — has been re-formulated. So why the upgrade? Well, the original tenofovir (tenofovir disoproxil fumarate — or TDF) has been found, in some cases, to cause renal problems. The new compound, dubbed TAF (tenofovir alafenamide), better targets the immune cells, which allows for reduced dosing — meaning less toxicity. (TAFs dose is 10 percent of TDFs.)
TDF — available in its own right as Viread, or found in single-tablet combos Atripla, Eviplera and Stribild — has also been associated with a small amount of bone loss (but this is usually within the first 12 months and not unique to TDF). So for people who have osteoporosis or who are already experiencing some renal dysfunction, TAF may be an alternative option. Your doctor will advise if a treatment change is required.
Ongoing research suggests people whose virus has built some resistance to TDF may have a better outcome with TAF instead — good news, considering tenofovir is the backbone drug for so many people living with HIV. As for side-effects, TAF has reported mild-to-moderate reactions including nausea, bloating, diarrhoea and headache.
In a nutshell: TAF offers equal effectiveness, but with less toxicity.