The World Health Organization (WHO) states that 33.4 million people around the world are infected with the human immunodeficiency virus (HIV), a sexually transmitted disease that severely weakens the patient's immune system. No cure exists for HIV or acquired immune deficiency syndrome (AIDS), the advanced stage of HIV. Treatment aims to slow down the progression of the disease and prolong the patient's life. Treatment is an aggressive regimen of drugs, termed highly active anti-retroviral therapy (HAART); the Mayo Clinic notes that an HIV patient is given three or more drugs with HAART.
Transcriptase Inhibitors
Transcriptase inhibitors are one group of drugs used for HIV treatment, which prevent the virus from replicating, according to the National Women's Health Information Center. Nucleoside analogue reverse transcriptase inhibitors (NRTIs), the first anti-retroviral drug for HIV, work by preventing the reverse transcriptase enzyme from replicating. Examples of NRTIs are abacavir, zidovudine, stavudine, lamivudine and didanosine. Another type of transcriptase inhibitor, non-nucleoside reverse transcriptase inhibitors (NNRTIs), attach themselves to the reverse transcriptase enzyme to deactivate the virus. Examples include etravirine, nevirapine, efavirenz and delavirdine. The Mayo Clinic states that nucleotide reverse transcriptase inhibitors (NtRTIs) are similar in mechanism to NRTIs but have faster response times. Tenofovir is the only approved drug in this class.
Protease Inhibitors
Unlike other anti-retroviral drugs, protease inhibitors (PIs) target the virus at the end of its replication cycle. In particular, PIs disrupt the HIV protease enzyme. Multiple PIs are available, including saquinavir, tipranavir, ritonavir, atazanavir, indinavir, nelfinavir, amprenavir and lopinavir/ritonavir. Another type of PI, darunavir, is given to a HIV patient when she does not respond positively to the other drugs.
Other Inhibitors
Other types of anti-retroviral drugs for HIV are given to patients who either have a resistant strain of HIV, or who are not responsive to transcriptase or protease inhibitors. Fusion inhibitors, for example, prevent membrane fusion between HIV cells and healthy cells. Enfuvirtide is a type of fusion inhibitor. Integrase inhibitors work by interfering in the replication of the HIV integrase enzyme; raltegravir is an example.
