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Pharmacology > Antiviral Agents > Flashcards

Antiviral Agents Flashcards

1
Q

Antiherpes drugs

A
  • Acyclovir
  • Ganciclovir
  • Cidofovir
  • Foscarnet
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2
Q

Acyclovir

A
  • Active aganist HSV-1/2 and VZV
  • Activated to acyclovir triphosphate, a competitive substrate for DNA polymerase –> cause chain termination and incorporation into viral DNA
  • Oral: used for treatment of mucocutaneous and genital herpes lesions. Also for prophylaxis in immunocompromised patients
  • IV: used for severe herpes disease, including encephalitis and neonatal HSV infection
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3
Q

Ganciclovir

A
  • Active against HSV and CMV
  • Triphosphorylated to form a nucleotide that inhibits DNA polymerase, do not cause chain termination
  • Used for prophylaxis and treatment of CMV retinitis and other CMV infections in immunocompromised patients
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4
Q

Cidofovir

A
  • Inhibits DNA polymerase of HSV, CMV, adenovirus and papillomavirus
  • Its phosphorylation does not require viral kinase
  • Used in CMV retinits, mucocutaneous HSV infections, and in genitaø warts
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5
Q

Foscarnet

A
  • Does not require phosphorylation for activity
  • Inhibits viral RNA polymerase, DNA polymerase, and HIV reverse transcriptase
  • Alternative drug for prophylaxis and treatment of CMV infections
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6
Q

Nucleoside reverse transcriptase inhibitors

A
  • Zidovudine (ZDV)
  • Didanosine (ddI)
  • Zalcitabine (ddC)
  • Lamivudine (3TC)
  • Stavudine (d4T)
  • Abacavir
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7
Q

Nucleoside reverse transcriptase inhibitors: Mechanism of action

A
  • Prodrugs converted by host cell kinases to triphosphates
  • Competitively inhibit binding of natural nucleotides to the dNTP-binding site of reverse transcriptase
  • Act as chain terminators
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8
Q

Zidovudine (ZDV)

A
  • Frequently used in combination drug regimens (HAART)
  • Used in prophylaxis against HIV infection
  • Azole antifungals and protease inhibitors may increase plasma levels of zidovudine
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9
Q

Nonnucleoside reverse transcriptase inhibitors

A
  • Nevirapine
  • Delaviridine
  • Efavirenz
  • Tenofovir
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10
Q

Nonnucleoside reverse transcriptase inhibitors: Mechanism of action

A
  • Do not require phosphorylation to be active
  • Do not compete with nucleoside triphosphate
  • Bind to a site on reverse transcriptase different form NRTIs
  • No cross-resistance with NRTIs
  • Resistance caused by pol gene mutation
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11
Q

Nevirapine

A
  • Currently used in alternative combination regimens
  • Effective i preventing HIV vertical transmission when given to mother at the onset of labor and to the neonate
  • Can cause Steven-Johnson syndrome
  • Blood levels increased by cimetidine and macrolides, decreased by rifampin
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12
Q

Delaviridine

A
  • Drug reaction major problem with this drug

- Metabolized by both CYP3A4 and CYP2D6

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13
Q

Efavirenz

A
  • Effective in HIV treatment when used in combination with 2 NRTIs
  • Metabolized by P450 - involved in drug interactions
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14
Q

Tenofovir

A
  • Do not require bioactivation via host cell kinases
  • Completly inhibits reverse transcriptase and cause chain termination
  • Used in HAART regimens
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15
Q

Protease inhibitors

A
  • Indinavir
  • Ritonavir
  • Saquinavir
  • Nelfinavir
  • Amprenavir
  • Lopinavir
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16
Q
  • Protease inhibitors: Mechanism of action
A
  • Inhibit the active site in the viral enzyme, aspartate protease (HIV-1 protease)
  • This enzyme is coded by the pol gene, and cleaves precursor polyproteins to form the final structural proteins of the mature virion core
  • Caused disorders in carbohydrate and lipid metabolism - hyperglycemia and insulin resistance, or hyperlipidemia
17
Q

Indinavir

A
  • Bioavailability inhibited in the presence of food

- Serum levels are increased by azole antifungals and decreased by rifamycins

18
Q

Ritonavir

A
  • Should be taken with meals

- Most common adverse effect: GI irritation and bitter taste

19
Q

Fusion inhibitors

A
  • Enfuviritide

- Maraviroc

20
Q

Enfuviritde

A
  • Binds to th gp41 subunit of the viral envelope glycoprotein
  • Prevent the conformational changes required for the fusion of the viral and cellular membranes
  • Resistance: mutation in env gene
  • Administered subcutaneously
21
Q

Anti-influenza agents

A
  • Amantadine
  • Rimantadine
  • Oseltamivir
  • Zanamivir
22
Q

Amantadine, Rimantadine

A
  • Inhibit an early step in replication of the influenza A virus
  • Prevent “uncoating” by binding to a protein M2 = protein that function as a proton ion channel required at the onset of infection to permit acidification of the virus core, which in turn activates viral RNA transcriptase
  • Used as prophylaxis against influenza A virus with 80% efficacy
23
Q

Oseltamivir, Zanamivir

A
  • Inhibits neuraminidases (NA) produced by influenza A and B viruses.
  • NA cleaves sialic acid residues from viral proteins and surface proteins of infected cells. Its function is to promote virion release and to prevent clumping of newly released virions
  • Used to impede viral spread
24
Q

Anti-hepatitis agents

A
  • Interferon-α (INF-α)
  • Lamivudine
  • Ribavirin
  • Adefovir
25
Q

Interferon-α: Mechanism of action

A
  • Increase the activity of Janus kinases (JAKS)
  • JAKS phosphorylate signal transducers and activators of transcription (STATS) to increase the formation of antiviral proteins
  • Activate host cell ribonuclease that preferentially degrades viral mRNA
  • Also promote formation of natural killer cells that destroy infected liver cells
26
Q

Interferon-α: Clinical

A
  • Used in chronic HBV as an individual agent or in combination with Lamivudine
  • Used in combination with Ribavirin to reduce progression of acute HCV to chronic HCV infection
  • Used in treatment of Kaposi’s sarcoma, papillomatosis, and topically for genital warts
27
Q

Adefovir

A
  • Competitively inhibit HBV DNA polymerase
  • Incorporate into viral DNA –> chain termination
  • Used to suppress HBV replication and improves liver histology and fibrosis
28
Q

Lamivudine

A
  • NRTI
  • Active in chronic HBV
  • Can be used in lower doses for hepatitis than for HIV infection - longer intracellular half-life in HBV
  • Suppresses HBV replication and is remarkably nontoxic
29
Q

Ribavirin

A
  • Inhibits guanosine triphosphate formation
  • Prevents capping of viral mRNA
  • Block RNA-dependent RNA polymerase
  • Inhibit replication in influenza A and B, parainfluenza, RSV, paramyxoviruses, HCV, and HIV
  • Used in combination with INF-α in chronic HCV infection in patients with compensated liver disease

Pharmacology (16 decks)

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