Aids / HIV

Antiretroviral therapy

Human Immunodeficiency Virus (HIV) is an RNA virus and the drugs used to treat HIV infection are known as antiretroviral drugs.

The antiretroviral drugs in this section work by various mechanisms to prevent the replication and spread of HIV, a virus that specifically attacks immune cells called CD4+ cells that are involved in fighting infection. If too many CD4+ cells are destroyed, the body can no longer fight infection efficiently and this can lead to acquired immune deficiency syndrome (AIDS). The aim of antiretroviral therapy is to reduce amount of virus (viral load) down to a low level; allowing the numbers of CD4+ cells to increase, so that the immune system can recover.

Some of our antiretroviral medications contain a single drug that should be used in combination with another medication preferably with a different mechanism of action, to comply with a treatment regime known as highly active antiretroviral therapy (HAART) that is designed to help prevent development of viral resistance to treatment.

Several of our antiretroviral medications already contain a fixed dose combination of drugs in a single tablet, to make it easier to use a suitable drug combination.

Sub-classes of antiretroviral drugs

The various antiretroviral drugs available for treatment of HIV infection act directly on virus-specific enzymes to prevent the virus from growing, but they do not kill the virus.

Several drugs work by inhibiting the action of the viral-specific enzyme reverse transcriptase (RT) which is needed for the virus to be able to replicate. This happens by one of two ways.

Either the drug is a nucleoside analogue reverse transcriptase inhibitor (NRTI), which means that it blocks the action of RT by competing with one of the nucleosides, or molecular building blocks needed to transcribe the viral RNA into DNA. The analogue becomes incorporated into the chain of newly synthesized viral DNA instead of the correct nucleoside, preventing viral replication. Another mechanism for blocking the action of RT is by binding to a specific active site on the enzyme disrupting the way it functions. These are called non-nucleoside reverse transcriptase inhibitor (NNRTI).

The viral protease enzyme is another drug target. This enzyme is needed during final stages of the viral replication cycle so that fully active mature virus can be released to infect new cells. Protease inhibitors result in the production of immature, non-infectious viral particles.