Lopinavir/ritonavir (LPV/r), sold under the brand name Kaletra among others, is a fixed dose combination medication for the treatment and prevention of HIV/AIDS.[1] It combines lopinavir with a low dose of ritonavir.[1] It is generally recommended for use with other antiretrovirals.[1] It may be used for prevention after a needlestick injury or other potential exposure.[1] It is taken by mouth as a tablet, capsule, or solution.[1] Common side effects include diarrhea, vomiting, feeling tired, headaches, and muscle pains.[1] Severe side effects may include pancreatitis, liver problems, and high blood sugar.[1] It is commonly used in pregnancy and it appears to be safe.[1] Both medications are HIV protease inhibitors.[1] Ritonavir functions by slowing down the breakdown of lopinavir.[1] Lopinavir/ritonavir as a single medication was approved for use in the United States in 2000.[1] It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.[2] The wholesale cost in the developing world is 18.96 to 113.52 a month.[3] In the United States it is not available as a generic medication and costs more than US$200 for a typical month supply as of 2016.[4] As of 2006, lopinavir/ritonavir forms part of the preferred combination for first-line therapy recommended by the US United States Department of Health and Human Services in 2006.[5] The most common adverse effects observed with lopinavir/ritonavir are diarrhea and nausea. In key clinical trials, moderate or severe diarrhea occurred in up to 27% of patients, and moderate/severe nausea in up to 16%.[6] Other common adverse effects include abdominal pain, asthenia, headache, vomiting and, particularly in children, rash.[6] Raised liver enzymes and hyperlipidemia (both hypertriglyceridemia and hypercholesterolemia) are also commonly observed during lopinavir/ritonavir treatment. Lopinavir/ritonavir is anticipated to have varying degrees of interaction with other medications that are also CYP3A and/or P-gp substrates.[7] People with a structural heart disease, preexisting conduction system abnormalities, ischaemic heart disease, or cardiomyopathies should use lopinavir/ritonavir with caution.[8] On 8 March 2011 the U.S. Food and Drug Administration notified healthcare professionals of serious health problems that have been reported in premature babies receiving lopinavir/ritonavir oral solution, probably because of its propylene glycol content. They recommend the use should be avoided in premature babies.[9] Lopinavir was developed by Abbott in an attempt to improve on the HIV resistance and serum protein-binding properties of the company's earlier protease inhibitor, ritonavir.[10] Administered alone, lopinavir has insufficient bioavailability; however, like several HIV protease inhibitors, its blood levels are greatly increased by low doses of ritonavir, a potent inhibitor of cytochrome P450 3A4.[10] Abbott therefore pursued a strategy of co-administering lopinavir with sub-therapeutic doses of ritonavir, and lopinavir is only marketed as a co-formulation with ritonavir. It is the first multi-drug capsule to contain a drug not available individually. Lopinavir/ritonavir was approved by the USA FDA on 15 September 2000, and in Europe in April 2001. Its patent was scheduled to expire in the US on June 26, 2016. Abbott Laboratories was one of the earliest users of the Advanced Photon Source, a national synchrotron-radiation light source at Argonne National Laboratory. One of the early research projects undertaken at the Advanced Photon Source was the Human Immunodeficiency Virus. Using X-ray crystallography, researchers found the points of attack of the HIV protease inhibitors – agents that block the breakdown of proteins. Protease inhibitors stop HIV from making new copies of itself by blocking the last step in the process, when the virus attempts to replicate – and out of that discovery came the drug Kaletra/Aluvia.[11] As a result of high prices and the spread of HIV infection, the government of Thailand issued a compulsory license on 29 January 2007, to produce and/or import generic versions of lopinavir and ritonavir.[12] In response, Abbott Laboratories withdrew its registration for lopinavir and seven of their other new drugs in Thailand, citing the Thai government's lack of respect for patents.[13] Abbott's attitude has been denounced by several NGOs worldwide, including a netstrike initiated by Act Up-Paris and a public call to boycott all of Abbott's medicines by the French NGO AIDES.[14]