Antiviral Drugs

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton  

Introduction

Antiviral drugs are prescription medicines (pills, liquid, an inhaled powder, or an intravenous solution) that fight against viruses in the body. Key Points about antiviral drugs:

  • Able to enter the cells infected with virus
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  • Interfere with viral nucleic acid synthesis and/or regulation
  • Some agent interfere with virus ability to bind with cell
  • Some agents stimulate the body's immune system

Mechanism of Action (in combination or single action)

  • Inhibit viral attachment
  • Prevent genetic copying of virus
  • Prevent viral protein production, vital for reproduction of virus.[1]
Diagram on R: Schematic description of the mechanism of the four classes of currently available antiviral drugs : fusion inhibitors (interfere with the binding, fusion or entry of a virion), reverse-transcriptase inhibitors (interfere with the translation of viral RNA into DNA), integrase inhibitors (block the viral enzyme integrase, that inserts the viral genome into the DNA of the host cell), protease inhibitors (block proteolytic cleavage of protein precursors that are necessary for the production of infectious viral particles)
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Virus Description

Viruses are obligate (ie by necessity) intracellular parasites.

  • They lack both a cell wall and a cell membrane
  • They do not carry out metabolic processes.
  • It must attach to and enter a host
  • It then uses the host cell's energy to synthesis protein, DNA and RNA
  • A virus is difficult to kill as it lives inside the hosts cell and a drug that kills the virus may also kill the cell[1].

Retroviruses are a type of virus in the viral family called Retroviridae. The antiviral drugs target diverse group of viruses such as herpes, hepatitis, and influenza viruses. Whereas antiretroviral are the drugs that are used to fight retrovirus infections which mainly include HIV. Different classes of antiretroviral drugs act on different stages of the HIV life cycle.[2].

There are many technical differences between viruses and retroviruses.

  • Generally, the main difference between the two is how they replicate within a host cell.
  • Retroviruses use RNA as their genetic material and are named for a special enzyme that’s a vital part of their life cycle — reverse transcriptase (Transcription is the process in cells by which an enzyme makes a copy of DNA from RNA. The enzyme that makes the DNA copy is called reverse transcriptase and is found in retroviruses).
  • The key steps that differentiate retroviruses from viruses are reverse transcription and genome integration[2].

Antiviral Drug Development

The emergence of antivirals is the product of a our newly acquired knowledge of the genetic and molecular function of organisms letting us better understand the structure and function of viruses, major advances in the techniques for finding new drugs, and the pressure placed on the medical profession to deal with the human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS).

  • First experimental antivirals were developed in the 1960s, mostly to deal with herpes viruses, and were found using traditional trial-and-error drug discovery methods.
  • Only in the 1980s, when the full genetic sequences of viruses began to be unraveled, did researchers begin to learn how viruses worked in detail, and exactly what chemicals were needed to thwart their reproductive cycle.[3]

Few drugs are selective enough to prevent viral replication without injury to the infected host cells.

Therapy for viral diseases is further complicated by the fact that the clinical symptoms appear late in the course of the disease, at a time when most of the virus particles have replicated.[4]

The 4 and 1/2 minute video below gives a good summary of Antiviral drugs
[5]

Virus Diseases

  • Viruses are composed of a single DNA or RNA inside a protein coat.
  • Viruses must enter a cell in order for them to carry on with their metabolic processes.
  • Upon successful entry, viruses inject their DNA or RNA to the cell and the cell is altered in such a manner that it is now “programmed” to control the metabolic processes that the virus needs to survive.
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Because viruses are contained in the cells, researchers find it difficult to develop antiviral drugs including vaccines.

Viruses that respond to antiviral therapy include

Antivirals - For Whom

Who should take antiviral drugs?

Most people will not require antivirals as they will have a mild illness and will recover quickly. In these cases the risk of side-effects from these drugs may outweigh the benefit of taking them.

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Candidates for antivirals are individuals who have:

  • Higher risk for complications from influenza
  • Adults 65 or older
  • Chronic diseases such as heart, lung, or kidney disease
  • Under age 4
  • Anyone with a compromised immune system.[7]

Note: Important client aware of

  • Need for good (hand) hygiene when taking and proper application of ointments, aerosols powders
  • Not a cure but help to manage symptoms

Side Effects

Like all medicines, antivirals can cause side effects, although not everyone gets them.

Common side effects include:

  • nausea and vomiting
  • diarrhoea and stomach ache
  • headache

These side effects mostly occur after the first dose of the medicine and will usually stop as treatment continues.

Less common side effects include:

  • sleeping difficulties
  • skin reactions
  • heart rhythm abnormalities
  • hallucinations
  • abnormal behaviour[7]

Ongoing Research

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The discovery and development of antiviral drugs, compounds, and clinical methods to prevent viral infections is beneficial for Global Health.

  • The emergence and re-emergence of many viruses is a threatening alarm for both animal and human populations. eg Zoonotic viruses can cause extensive morbidity and mortality, take Covid 19.
  • Preventive vaccines that provide protection are available for only a limited number of viruses.
  • New drug therapies combine antivirals to increase efficacy and to avoid the development of drug resistant strains. These strategies are effective for viruses such as HIV.
  • Clearly there is a need to expand our drug arsenal to address the wide diversity of viruses and this is why ongoing research is important.[8]

References

  1. 1.0 1.1 Slide shear Antivirals Available from:https://www.slideshare.net/jben501/nurserevieworg-antivirals-updates-teaching-pharmacology-terminology-for-lpn-nursing-students-presentation (last accessed 3.6.2020)
  2. 2.0 2.1 Healthline Retrovirus Available from:https://www.healthline.com/health/what-is-a-retrovirus (last accessed 4.6.2020)
  3. Wikipedia Antiviral drugs Available from:https://en.wikipedia.org/wiki/Antiviral_drug (last accessed 3.6.2020)
  4. nclx Antiviral drugs Available from:https://brilliantnurse.com/nclex-antiviral-drugs/ (last accessed 3.6.2020)
  5. ALI LA medical Antiviral drugs Available from: https://www.youtube.com/watch?v=IOXEAAHmzT4 (last accessed 3.6.2020)
  6. Nurselabs Viral diseases Available from:https://nurseslabs.com/antiviral-drugs/#disease_spotlight_viral_diseases (last accessed 3.6.2020)
  7. 7.0 7.1 nhs antiviral meds Available from:http://www.nhsborders.scot.nhs.uk/media/209209/Antiviral-medication-June-2014.pdf (last accessed 3.6.2020)
  8. Peerteechz antivirals Available from:https://www.peertechz.com/journals/annals-of-antivirals-and-antiretrovirals/about#:~:text=The%20antiviral%20drugs%20target%20diverse,of%20the%20HIV%20life%20cycle. (last accessed 4.6.2020)