Medications for treating human immunodeficiency virus, HIV, infection have changed AIDS from a near-universally fatal disease to one that is manageable for long periods. These medications work by suppressing the ability of HIV to make copies of itself. The virus has a complex life cycle, so its replication can be interrupted at several points. Different drugs target the virus at different points in its life cycle. Since the virus quickly mutates to become resistant to a single drug, effective HIV treatment regimens combine different types of medications.
NRTIs
Nucleoside reverse transcriptase inhibitors, NRTIs, work by stopping the process of reverse transcription. Reverse transcription is the process by which HIV copies its own RNA into DNA that can alter the behavior of immune system cells. According to an article published in the July 21, 2010, issue of "The Journal of the American Medical Association," current treatment guidelines specify that HIV medication regimens should contain two drugs from the NRTI class. Tenofovir and emtricitabine are the most commonly prescribed NRTIs. A fixed-dose combination of these two medications is available under the trade name Truvada.
NNRTIs
In addition to the two NRTIs, an HIV medication regimen should contain a third drug of a different type. Non-nucleoside reverse transcriptase inhibitors, NNRTIs, also inhibit reverse transcription, but they do this using a different mechanism than the NRTIs, according to the text, "Harrison's Principles of Internal Medicine." Because the mechanisms are different, NNRTIs can be used effectively as a third drug. The most commonly prescribed NNRTI is efavirenz, says "JAMA." Efavirenz, along with tenofovir and emtricitabine, is available as a fixed-dose combination pill under the trade name Atripla.
PIs
Protease inhibitors, PIs, are another class of medications that can be used as the third drug in an HIV regimen. PIs inhibit HIV from assembling the proteins it needs to replicate itself. PIs have a tendency to cause cholesterol problems, but unlike NNRTIs, they can be given only once a day. So they are sometimes prescribed as a third drug in patients for whom adherence to a medication schedule is a problem. Atazanavir is the most commonly prescribed PI, because it has less potential to cause cholesterol problems than other PIs, according to "JAMA." Like all PIs, atazanavir is more effective when taken with small amount of another PI called ritonavir. Lopinavir is the only PI available as a single pill combined with ritonavir, sold under the trade name Kaletra, so sometimes it is prescribed instead of atazanavir for patients who have difficulty keeping track of multiple medications.
References
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper; 2005
- "JAMA": Antiretroviral Treatment of Adult HIV Infection
