Resistance

As ritonavir (Norvir) is now rarely given as the only protease inhibitor in an HIV treatment regimen, ritonavir resistance rarely develops. However, previous studies have found that mutations in the protease gene at codons 82 and 84 are associated with resistance to ritonavir, as well as mutations M46I/L, I50V, I54V and L90M. The I84V mutation reduces susceptibility to all available protease inhibitors, whereas V82A/T/F/S reduces susceptibility to indinavir and lopinavir.

HIV that is resistant to ritonavir is usually entirely cross-resistant to indinavir (Crixivan), and responses to nelfinavir (Viracept) and saquinavir (Invirase) tend to be poor.

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.