36)Antiviral drugs

Question 1

Antiviral drugs

Answer 1

Used to treat viral infections

Many antiviral drugs are purine or pyrimidine analogues

Many are prodrugs ⇢ must be phosphorylated by viral/cellular enzymes in order to become active

Question 2

Classification

Answer 2

Anti-herpes viral agents

• Acyclovir, Valacyclovir
• Idoxuridine + Tromantadine

Anti-influenza viral agents

• Amantadine, Rimantadine
• Oseltamivir + Zanamivir

Used too treat cytomegalovirus infection:

• Ganciclovir, Cidofovir + Fomivirsen

Question 3

Classification - Anti-retroviral agents/Anti-HIV drugs + Drugs used for viral hepatitis

Answer 3

NRTIs - Nucleoside reverse transcriptase inhibition

• Zidovudine + Didanosine

NNTIs - Non ‘’

• Nevirapine

Protease inhibitors

• Ritonavir

Used for viral hepatitis

• Interferon alpha + Ribavirin

Question 4

Characteristics

Answer 4

• Able to enter cells infected by a virus
• Interfere with viral nucleic acid synthesis/regulation
• Interfere w/ability of virus to bind to cells
• Stimulates body’s immune system - healthy immune system works synergistically w/drug
• Purine/Pyrimidine analogues
• Clinical efficiency ⇢ depends on achieving inhibitory concentration at site of infection within infected cells

Question 5

Acyclovir

Answer 5

PD ⇢ inhibits viral DNA synthesis

PKs:⇢ poor oral absorption, Lipophilic + excreted by kidneys mainly

Side effects:

• Nausea, diarrhoea + headache
• Rashes, sweating + ⇣ BP
• Nephrotoxicity + Neurotoxicity

Clinical use

• Treats herpes simplex + varicella-zoster virus

Question 6

Anit-Influenza drugs

Answer 6

Caused by 3 RNA viruses- Influenza A, B or C

Neuraminidase inhibitors ⇢ Oseltamivir + Zanamivir

• Inhibit neuraminidase enzyme ⇢ locks virus into cell
• Oseltamivir ⇢ orally taken ⇢ prevents flu for those over 1 yrs age
• Zanamivir ⇢ treats those over 7 yrs
• Both immediately effective after flu symptoms have set
• Side effects ⇢ Nausea, vomiting, runny nose, cough + diarrhoea

M2 protein inhibitors ⇢ adamantane derivatives

Question 7

HIV treatment NRTIs

Answer 7

Nucleoside Reverse transcriptase inhibitors ⇢ Zidovudine + Didanosine

• Prevent acute infection of cells ⇢ do not affect already infected cells
• Resistance to these may occur ⇢ ineffective long term
• Side effects ⇢ neuropathy
• Zidovudine ⇢ hepatotoxicity
• Didanosine ⇢ pancreatitis

Question 8

NNTIs

Answer 8

Nevirapine

• Non nucleoside antimetabolites
• Prone to adverse DDIS
• Side effects ⇢ rash + CNS toxicity

Question 9

Protease inhibitors

Answer 9

Saquinavir

• Inhibit protease enzyme ⇢ responsible for virus assembly
• Side effects ⇢ unusual fat distribution + insulin resistance