What is lopinavir and ritonavir (LPV/r)?

Lopinavir-ritonavir (LPV/r) is a drug combination available under the brand name Kaletra. It is used to treat HIV infection. Lopinavir is a protease inhibitor that slows the spread of HIV (human immunodeficiency virus) throughout the body by interfering with the enzyme needed by the virus to replicate. Ritonavir is added because it inhibits an enzyme that metabolizes lopinavir, resulting in higher lopinavir blood levels. Lopinavir-ritonavir cannot cure HIV infection nor keep HIV from being transmitted to other people.