Today, there are a number of different registered HIV medicines and new ones are in development. Progress in recent years has meant that fewer tablets and fewer doses need to be taken daily. HIV treatment consists of combination therapy with multiple medications. When treatment begins, medicines are selected from four different classes:
- Nucleoside/nucleotide reverse transcriptase inhibitors (NRTI)
- Non-nucleoside reverse transcriptase inhibitors (NNRTI)
- Protease inhibitors (PI)
- Integrase inhibitors (INSTI)
How do the medicines work?
HIV treatment aims to prevent the reproduction of the virus and thus the attack on the white blood cells (immune cells). The virus needs several biochemical processes to enable it to penetrate the white blood cells, multiply and then exit the cells to infect new ones. HIV medication prevents or disturbs these processes.
HIV treatment exploits different attack strategies to prevent HIV from multiplying. Some medicines block the virus from the immune cells and others destroy or prevent the virus production within immune cells, or prevent them from leaving in a form where they can attack new cells.
Risk of mutation and resistance development
HIV can multiply quickly and create new “versions” of the virus which differ slightly from the original, known as mutation. In practice, this means that an HIV positive person will eventually have many different variants of the virus, but none are produced in large enough quantities to overtake the majority of the original virus.
When starting treatment, the original virus will be blocked by HIV medicine. When the treatment only uses a single drug, a mutation could be formed that can withstand it. The mutated virus will escape the “blockade” created by the HIV drug. The viruses will continue to multiply and with time will overtake the original virus. Treatment will no longer work and this is called resistance.
The same can happen when two drugs are taken simultaneously, but the risk of resistance development is less. The more medicines are administered, the less risk there is for resistance development. Therefore a “cocktail” of several drugs is often given simultaneously. In recent years, fewer daily doses have been needed.
The goal of treatment is to find a combination of drugs that reduces viral load to below detectable levels and keeps it there. Then the risk of new mutations and resistance is small.
The correct use of HIV medicine will usually be very effective in preventing the production of new viruses and reduce the risk of HIV mutations. However, this requires that the virus will constantly be “bombarded” with drugs that interfere with the reproduction process. Therefore, it is vital to take HIV medicine according to a rigid schedule and in the right dose every day.