In previously untreated HIV-1
infection, one first-line therapeutic option is to combine
efavirenz, a non-
nucleoside reverse transcriptase inhibitor, with
tenofovir and
emtricitabine.
Rilpivirine, another non-
nucleoside reverse transcriptase inhibitor, has been approved in the European Union for the treatment of antiretroviral-naive patients with low viral load. Two double-blind "non-inferiority" trials compared
rilpivirine- and
efavirenz-based combination
therapy in a total of 1368 previously untreated patients. Efficacy was similar with respect to the primary endpoint: 80% of patients had viral load below 50 copies/ml after 48 weeks of treatment. In these trials, combinations containing
rilpivirine appeared less effective than those containing
efavirenz in patients with high viral load (above 100 000 copies/ml). Overall, the risk of virological failure appeared to be higher with
rilpivirine than with
efavirenz (20.4% versus 18% after 196 weeks). In addition, the potential for cross-resistance to other non-
nucleoside reverse transcriptase inhibitors in case of virological failure appeared to be higher with
rilpivirine than with
efavirenz. Compared with the known adverse effect profile of
efavirenz,
rilpivirine was associated with less
rash (17% versus 31%) and
dizziness (10% versus 29%). The incidence of depression appeared similar with the two drugs. In contrast, serum
creatinine elevation was more frequent with
rilpivirine (5% versus < 1%).
Gallstones and
adrenal insufficiency are also likely to be more frequent with
rilpivirine. High doses of
rilpivirine prolong the QTc interval.
Rilpivirine carries a risk of pharmacokinetic interactions with many other drugs, including inducers and inhibitors of
cytochrome P450 isoenzyme CYP3A4, drugs that increase gastric pH, and drugs transported by
P-glycoprotein.
Rilpivirine also carries a high risk of pharmacodynamic interactions, notably with drugs that prolong the QTc interval. In practice, as
rilpivirine has no proven therapeutic advantages, when combination
therapy containing a nonnucleotide
reverse transcriptase inhibitor is chosen for previously untreated patients, it is better to continue to use
efavirenz, a better-known
drug that creates fewer problems in case of treatment failure.