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AntiViral Drugs
Therapy Difficulties
Viruses depend on the host metabolic machinery for replication so selectivity is a problem.
Late clinical symptoms
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.
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.
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
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.
Neuroaminidase InhibitorsAdverse Effects
Oseltamivir
1. GI discomfort
2. Nausea
Zanamivir
1. Irritation of the RT.
2. Avoided in asthma ,chronic obstructive respiratory diseases.
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.
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
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.
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.
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.
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.
RibavirinMode of Action
The drug is converted into 5’-phosphate derivatives (ribovirin triphosphate)
RTP inhibit GTP formation and interfearing with mRNA formation.
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.
RibavirinAdverse Effects
Anemia Elevated Billirubin Some teratogenic effects
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