People who use dolutegravir are unlikely to develop drug resistance, but the odds are greater if it is used alone or with companion drugs that are not fully active. Dolutegravir—sold alone as Tivicay and a component of the Dovato, Juluca and Triumeq single-tablet regimens—is a potent integrase inhibitor with a high barrier to resistance. It is a recommended first-line option in U.S. treatment guidelines and one of the most widely used HIV medications worldwide. The RESIST study looked at 599 mostly treatment-experienced people in eight countries who had a detectable viral load despite taking a dolutegravir-based regimen. Genotypic resistance testing showed that 14% had a detectable integrase resistance mutation, and 3% had more than one. The risk of resistance was greatest for people who used dolutegravir alone and was also higher for those who used dolutegravir plus lamivudine without a third drug. Resistance was more likely among people who had NRTI resistance mutations, which could mean dolutegravir was essentially acting as monotherapy.