Kaletra is a fixed-dose combination containing the anti-HIV drugs lopinavir and ritonavir. Lopinavir is only available in Kaletra capsules, tablets and oral solution. However, ritonavir, which is used to boost lopinavir levels in the blood, is also marketed separately as Norvir.

Protease inhibitors block the activity of the HIV protease (or proteinase) enzyme to slow HIV replication and delay damage to the immune system. For more information on how protease inhibitors work, see Protease inhibitors.

Kaletra is made by Abbott Laboratories. It was approved for marketing in the United States in September 2000 and in the European Union in April 2001.