##antiviral drugs

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AntiViral Drugs

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Page 1: ##Antiviral Drugs

AntiViral Drugs

Page 2: ##Antiviral Drugs

Therapy Difficulties

Viruses depend on the host metabolic machinery for replication so selectivity is a problem.

Late clinical symptoms

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Treatment of Respiratory Virus Infections Influenza Type A , B and RSV Immunization is a better approach for type A Antiviral drugs are used when

Allergy 2 the vaccine. Outbreak due 2 Immunological variant of the viruse not

covered by the vaccine Outbreak in an unvaccinated group.

3 groups of drugs Neuraminidase inhibitors. Inhibitors of viral uncoating. Ribavirin.

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Neuroaminidase InhibitorsOseltamivir Zanamivir

Effective against type A,B influenza. They do not interfere with vaccination

process. B4 exposure they prevent infection.

within 24-48 hours they affect the intensity and duration of symptoms.

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Neuroaminidase InhibitorsMode of Action

Neuroaminidase help in the release of the virion from the cell after replication.

Neuroaminidase inhibitors prevent this process and thus preventing the continuing of the virus life cycle

Virions accumulate at the internal infected cell surface

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Neuroaminidase InhibitorsPharmacokinetics

Oseltamivir

1. Orally Active

2. Metabolized by the liver

3. Eleminated in the urine

Zanamivir

1. Inhaled or intranasally.

2. Eliminated in the urine.

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Neuroaminidase InhibitorsAdverse Effects

Oseltamivir

1. GI discomfort

2. Nausea

Zanamivir

1. Irritation of the RT.

2. Avoided in asthma ,chronic obstructive respiratory diseases.

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Inhibitors of Viral UncoatingAmantadineRimantadine

Limited to influenza A viruse. 70-90% effective in the prevention of the

infection if used at the time of exposure of before it.

They reduce the duration and the severity of the symptoms.

Doesn’t impair the vaccination process but used as a supplement to provide protection till the antibodies r produced.

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Inhibitors of Viral Uncoating

Mode of Action Blocking the viral membrane protein M2.

M2 is important as an ion channel for the fusion of the viral membrane with the cell membrane forming the endosome

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Inhibitors of Viral Uncoating

Pharmacokinetics Amantadine

1. A – well absorbed orally

2. D – distributes through out the body and crosses the BBB.

3. M – not extensively metabolized.

4. E – in the urine.

Rimantadine.

1. A – well absorbed orally.

2. D – does not cross the BBB as much as Amantadine.

3. M – metabolized by the liver.

4. E – in the urine.

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Inhibitors of Viral Uncoating

Adverse Effects. Amantadine1. Neurological symptoms.

• Insomnia,dizziness.

2. Carefully employed in patients with

• psychological diseases , cerebral atherosclerosis , renal impairment ,epilepsy.

3. GI intolerance.4. Used with caution in

pregnant and nursing patients.

Rimantadine1. Fewer CNS problems.2. GI intolerance3. Used with caution in

pregnant and nursing patients.

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Inhibitors of Viral Uncoating

Resistance Result from a change in one amino acid of the M2 matrix protein.

Develop in 50% in treated patients Can be tranmitted.

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Ribavarine

Effective against RNA and DNA viruses. Used in the treatment of infants with RSV

infections. Effective in chronic hepatitis C infections

when used with IF-alfa-2b.

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RibavirinMode of Action

The drug is converted into 5’-phosphate derivatives (ribovirin triphosphate)

RTP inhibit GTP formation and interfearing with mRNA formation.

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RibavirinPharmacokinetics

Effective orally and IV A – increased when taken with a fatty meal. Aersol is used in certain resp. conditions

Treatment of RSV infection. D – Retention in all tissues except for the

brain. E – in the urine.

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RibavirinAdverse Effects

Anemia Elevated Billirubin Some teratogenic effects