antivirals key issues

8/8/2019 Antivirals Key Issues

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Antivirals

Discussions & Key Issues

Dr. Md. Mostafizur Rahman

MBBS, FCPS (Med) Course

Registrar

Delta Medical College, Mirpur-1, Dhaka.


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Key Issues

General principles

Drug use strategies

Other issues

Types of drug to stockpile

Use of antivirals for containment and

intervention around early cases


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Antiviral Drug

Drugs : for treating viral infections

Specific antivirals are used for specific viruses. Antiviral drugs do not destroy their target

pathogen; instead they inhibit their development.

Most of the antivirals now available are HIV,herpes viruses, the hepatitis B and C viruses andinfluenza A and B viruses.


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History

Vaccines were effective in preventing many viraldiseases, they could not help once a viral infection

set in. But no drugs to treatviral infections.

Treating the symptoms and waiting for thedisease to run its course.

The first experimental antivirals were developed inthe 1960s, to deal with herpes viruses.


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Virus life cycle

Viruses consist of

1. a genome and

2. a few enzymes stored in a capsule (capsid),

3. and covered with a lipid layer ('envelope').

Viruses cannot reproduce on their own, so theyneed host cell to produce copies of themselves,thus producing the next generation.


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Depending on the species of virus, but they all sharea general pattern:

1. Attachment to a host cell.

2. Release of viral genes and enzymes into the host cell.

3. Replication of viral components using host-cell .

4. Assembly of viral components into complete viral particles.5. Release of viral particles to infect new host cells.


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Vaccines are very effective on stable viruses.

It is difficult to deploy vaccine againstrapidly mutating viruses, such as influenza (which is updated every year) and HIV.

Antiviral drugs are particularly useful in thesecases.


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Anti-viral targeting

The general idea behind antiviral drug design is toidentify viral proteins, that can be disabled.

The targets should be common across many strainsof a virus, so that a single drug will have broadeffectiveness.

For example, a researcher might target a criticalenzyme synthesized by the virus.


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Anti-virals interfere with the ability of a virus to

infiltrate a target cell.

Approaches by life cycle stage :

Entry inhibitor

Uncoating inhibitor


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The virus go through a sequence of steps:

1. beginning with binding to a specific "receptor"

molecule on the surface of the host cell2. and the virus "uncoating" inside the cell

3. and releasing its contents.

Viruses that have a lipid envelope must also fusetheir envelope with the target cell, before they canuncoat.


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The first successful antiviral, acyclovir, is a nucleosideanalogue, and is effective against herpesvirus

infections.

The first antiviral drug to be approved for treating

HIV, zidovudine is also a nucleoside analogue.


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Immune system stimulation

A second category of tactics for fighting viruses.

encouraging the body's immune system to attackthem


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One of the best-known of this class of drugs areinterferons,

which inhibit viral synthesis in infected cells.

Human interferon named "interferon alpha" is well-established as treatment for hepatitis B and C,

and other interferons are also being investigated astreatments for various diseases.


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antivirals key issues

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