Pharmacological prevention of HIV/AIDS

We have come to admit that HIV/AIDS is now part of us. It is everywhere and nobody can be trusted to be HIV negative. There are times I even doubt my HIV status that I have to take several tests just in case the previous test showed false results. This calls for better prevention of HIV. When everything fails, then pharmacological prevention of HIV is the next best option.
There are many methods of preventing HIV infection which rangefrom abstinence to use of protection. We won’t concentrate much on them since much has been said about them and it has become like song which people just enjoy and do nothing about.


Barrier method especially is a major problem with married couples who will start suspecting each other. In married couples, HIV infection comes from one of the partners. In case this happens, we want to protect the HIV negative partner. When one partner is infected and the other is not, we call that a Discordant couple. This is where pharmacological prevention of HIV comes in. 
Commercial sex workers is another group of people we want to protect. They are exposed to all types of HIV strains everyday from their customers. Because not all of them can use protection during sex, then we advocate for pharmacological prevention.


Mother to child transmission is a must. This is done to prevent transmission of the virus from the mother to the unborn child. The idea is to keep mother’s viral load lowest possible.
There are two types of HIV prevention using medicines, Pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP)
Before we get to the two types of prevention, we will first look at how medicines used in treatment of HIV/AIDS work. They simply work by preventing multiplication of the virus or preventing fusion of the virus into the CD4+ T cells or inhibiting one of the important viral enzymes.


Viruses make their proteins as one long chain. Protease enzyme cuts the long protein chain into smaller functional proteins. These are the proteins that the virus will use to carry out its activities. When we use protease inhibitors, these proteins are not available and the virus activities shut down.
The other intervention is to present the virus with false DNA building blocks. These are analogues (structurally similar molecules) of nucleotides and nucleosides that do not support lengthening of DNA. They lack hydroxyl (OH) groups at the 3’ end which are required for DNA chain lengthening. The DNA synthesis ends prematurely and the virus cannot multiply.


The other drugs prevent the virus from fusing into the CD4+ T cells and therefore locking them out from the only environment they can multiply. They are called fusion inhibitors.
A combination of above drugs is used for treatment of HIV/AIDS and most recent prevention. Strict compliance to medication is always advised as the virus will become resistant as soon as it is given a chance. It’s like giving the virus time to think and decide on new survival strategies. The virus gets to know what the drug was and finds ways of living with it.


Pre-exposure propylaxis (PrEP).
Pre-exposure prophylaxis, or PrEP, is whereby HIV negative people who are at risk of getting HIV take a pill everyday for prevention. The pill contains tenofovir, and emtricitabine. These are both nucleotide reverse transcriptase inhibitors.  This combination goes by the brand name Truvada. When someone is exposed to HIV through sex or injection drug use, these medicines can work to keep the virus from establishing a permanent infection.
When taken consistently, PrEP has been shown to reduce the risk of HIV infection in people who are at high risk by up to 92%. PrEP is much less effective if it is not taken consistently.
PrEP is a powerful HIV prevention tool and can be combined with condoms and other prevention methods to provide even greater protection than when used alone. But people who use PrEP must commit to taking the drug every day and seeing their health care provider for follow-up every 3 months.


Post exposure prophylaxis
Post-exposure prophylaxis, or PEP, is whereby HIV negative people who have come into contact with HIV either through unprotected sex or through work for example health care workers. PEP must be started within 72 hours after a recent possible exposure to HIV, but the sooner you start PEP, the better. The combination for this keeps on being updated. As per August 14, 2016, the WHO recommended combination is as follows. Lamuvidine, zidovudine plus boosted lopinavir. This should be taken for 28 days. PEP work by suppressing viral replication as the body fights the virus.


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Dr Mathu

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