Emtricitabine & Tenofovir

PrEP (emtricitabine + tenofovir) is an antiviral medication

Emtricitabine and tenofovir are used to prevent viral infections. This medicine is commonly referred to as PrEP which stands for Pre-Exposure Prophylaxis. Most often, PrEP is used in reference to the prevention of human immunodeficiency viruses (HIV), though it can prevent other viral infections as well.

PrEP works by preventing viruses from infecting a person's cells. We need to understand a little more about viruses themselves in order to understand how this works.

Viruses

Viruses are microorganism that can only replicate if they are inside a host cell. They consist of genetic material (DNA or RNA) wrapped in a protein capsule.

Viruses can't reproduce (replicate itself) without a host. When viruses find a host, we say that the host is infected with the virus. Once it has a host it uses the host's cells to replicate its genetic material and replicate itself.

If you've ever had the flu or chicken pox, then you've been a host for a virus!

Viruses are spread by a carrier that can infect other organisms. The carrier can be water, air or even other animals.

How Does it work?

Viruses are simple entities made of genetic material inside a protein capsid. Sometimes, this is surrounded by a protective membrane. Anti-viral medications cannot 'kill' viruses, as they are not alive. Antiviral medications generally focus on interrupting the process of replicating genetic material.

Genetic material in humans is DNA (deoxyribonucleic acid). It is converted by the cell into RNA (ribonucleic acid) inside the nucleus, and the RNA is transported into the cell membrane. Inside the cell membrane, the ribosome is involved in translating the information from the RNA molecule into proteins and other cell products.

DNA and RNA are made up of nucleotides that contain bases cytosine, thymine, adenine, guanine and uracil in long chains.

If the chain is incomplete, the instructions don't work properly. The anti-viral medication PrEP works by interrupting the formation of DNA strands.

PrEP works by mimicking the nucleotides adenosine and cytosine (two of the four basic building blocks of RNA and DNA).

When the cell uses the DNA containing the instructions for HIV, emtricitabine is incorporated instead of cytosine and tenofovir is incorporated instead of adenosine. Both emtricitabine and tenofovir stop the cell from further replicating the DNA strands. This stops the virus from being reproduced inside the host.

Scroll down to examine the similarities in structure between emtricitabine & cytosine and tenofovir & adenosine.