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Antiviral Drugs and their Classification

The medicines used to kill viruses and aid in increasing the immunity of a person are called antiviral drugs. These medications are prescribed by doctors to cure viral infections and to lower the risk of contraction of the same disease. In this article, we will study the different types of antivirals and how they act on these pathogens inside the host cells.

What are Antivirals?

There are many diseases that occur due to the invasion of specific viruses in our bodies. Even though our immune system is capable of fighting, killing, and resisting viral infections, we still need the aid of antiviral drugs to fight stubborn infections. Antivirals are specific organic compounds designed to kill viruses present in our body due to existing infection. These drugs are designed to inhibit certain biological processes that aid viruses to reproduce and increase in number. Viruses are considered to be pathogens that cannot be killed easily. They are inanimate objects when they are outside a host but regain life by using the resources of the vectors and hosts.

What are Viruses?

The microscopic pathogens that remain inanimate outside the hosts and regain their power of multiplication inside the hosts are called viruses. They have exceptional receptors that help them to identify healthy hosts and target them for reproduction. It can make copies of its genetic material very fast utilizing the resources of the host. Eventually, the host cell dies leaving more viruses in the system. These pathogens are eliminated using antiviral medications. The antiviral drugs list is given below with proper classifications.

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Classification of Antiviral Drugs

The organic compounds developed to stop the biological functions of the pathogenic viruses entering our body are called antivirals. These drugs are classified according to their mechanism of action in the following ways.

1. Nucleoside Analogs

Now that we know what are antivirals, let us understand the first classification of this genre of drugs. Nucleoside antivirals are synthetically prepared and manufactured to use against the viruses affecting a patient’s health. These organic compounds inhibit the viral polymerase enzyme and stop the cellular division or multiplication of the viruses. These compounds perfectly mimic this enzyme and inhibit the process of nucleotide production. It means that the pathogen virus is unable to produce genetic material and eventually loses its ability to replicate inside the host. Examples of antiviral drugs classification are acyclovir, penciclovir, valacyclovir, etc. Remdesivir is an example of antiviral drugs for COVID which falls in this class.

2. Non-Nucleoside Polymerase Inhibitors

As you can understand by its name, this type of antiviral drug does not replicate the shape of the nucleoside rather inhibits the process of replication by binding with the pyrophosphate site of the polymerase enzyme. This enzyme, as mentioned earlier, is used for nucleotide formation for genetic material production. Once blocked, the viruses cannot replicate their genetic material and die.

Drugs like phosphonoacetic acid and foscarnet work like a charm to stop the polymerase action of the viruses. The latter inhibits the DNA polymerase of herpes viruses and also the HIV reverse transcriptase. It has also shown excellent effectiveness against Hepatitis B viruses. The other molecules in this classification are efavirenz, delavirdine, and nevirapine. All these are non-nucleoside polymerase inhibitors following different mechanisms of action.

3. Protease Inhibitors

Another important antiviral drugs classification is protease inhibitors. This type of antiviral drug acts on the protease enzyme of the HIV viruses and distorts it. This enzyme is essential for the production of active HIV. If an HIV strain is resistive to such drugs, it means that it has gone through mutation to alter its protease structure. This is why a combination of antiviral drugs is prescribed for the benefit of the patients. The elimination of the viruses will become possible when a combination is done before they can mutate and evolve. The best examples of this antiviral classification are indinavir, saquinavir, ritonavir, amprenavir, and nelfinavir.

4. Other Types of Antiviral Drugs

The other types of these drugs have a different antiviral drugs structure from the classifications mentioned above. The best examples, in this aspect, are amantadine and rimantadine. These drugs are ineffective against influenza C and B. They can only act on Influenza A viruses. These medications are capable of reducing the intensity of the influenza infection but cannot cure it.

5. Interferon

There are three different types of interferon developed.

  • IFN-a or interferon-alpha

  • IFN-b or interferon-beta

  • IFN-g or interferon-gamma

IFN-a has 15 subtypes showing more than 85% similarity to the genetic structures of the viruses. This type of drug is produced by the leukocytes when there is a viral infection in the body. When used, this interferon marks the viruses better and increases the immune response. The natural killers or the WBCs are activated and sent to the targets to kill and destroy the viruses. Interferon also inhibits the replication process of the viruses thus halting the population and aiding the drugs to destroy the existing ones.

Refer to any antiviral drugs PDF to understand the classification of an antiviral drug in detail. This is the elaborate classification of these drugs according to their mechanism of action in a host against the pathogenic viruses.

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FAQs on Antiviral Drugs

1. How do antiviral medications work?

Ans: Antiviral medications inhibit a significant process that enables the viruses to replicate inside the host cells resulting in their deaths and halting their reproduction.

2. Why do we use a combination of antiviral drugs?

Ans: Viruses have the simplest genetic material. They can easily change it with the help of mutation and become resistant to the existing drugs. This is why a combination of antiviral medications is often prescribed in order to eliminate them before they mutate and replicate faster. This is by far the biggest drawback of antiviral medications.