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USMLE step 1 Rapid Review > Antivirals > Flashcards

Antivirals Flashcards

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USMLE® Step 1 flashcards
1
Q

Uncoating of a virus is blocked by which antiviral agent?

A

Amantadine

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2
Q

Amantadine specifically treats which infection by blocking viral uncoating?

A

Influenza A

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3
Q

Nucleic acid synthesis is blocked by which two antiviral classes?

A

Purine/pyrimidine analogs and reverse transcriptase inhibitors; usually antiretroviral drugs

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4
Q

Viral release from cells is blocked by which group of antiviral inhibitors?

A

Neuraminidase inhibitors (influenza)

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5
Q

What is the mechanism of action of amantadine when used as an antiviral agent?

A

Blocking viral penetration/uncoating (remember: “a man to dine” takes off his coat)

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6
Q

Amantadine is used to treat which two diseases?

A

Influenza A and Parkinsons disease

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7
Q

What three toxicities are associated with amantadine?

A

Ataxia, dizziness, and slurred speech; (remember: Amantadine blocks influenza A, and rubellA and causes problems with the cerebellA)

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8
Q

Which has fewer central nervous system adverse effects, amantadine or rimantidine?

A

Rimantidine, because it does not cross the blood-brain barrier

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9
Q

What is the mechanism of viral resistance to amantadine?

A

Mutated M2 protein has made 90% of all influenza A strains resistant to amantadine

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10
Q

In addition to use as an antiviral agent, why is amantadine useful in Parkinsons disease?

A

It causes release of dopamine from nerve terminals

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11
Q

Which enzymes do zanamivir and oseltamivir (Tamiflu) inhibit?

A

Influenza neuraminidase, decreasing release of progeny virus

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12
Q

Which strains of influenza do zanamivir and oseltamivir (Tamiflu) inhibit?

A

Both influenza A and B

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13
Q

The mechanism of action of ribavirin is through inhibiting the synthesis of _____ nucleotides by competitively inhibiting the enzyme _____ _____ _____.

A

Guanine; inosine monophosphate dehydrogenase

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14
Q

Which two infections is ribavirin used to treat?

A

Chronic hepatitis C virus and respiratory syncytial virus

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15
Q

What is a potential toxicity of ribavirin use?

A

Hemolytic anemia

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16
Q

What patient population should ribavirin not be given to?

A

Pregnant mothers (it is teratogenic)

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17
Q

What is the mechanism of action of acyclovir?

A

Acyclovir is a guanosine analog that terminates chains of viral DNA into which it is incorporated

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18
Q

Name three viruses for which acyclovir is used.

A

Herpes simplex virus, varicella zoster virus, and Epstein-Barr virus

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19
Q

Should acyclovir be used to treat herpes zoster?

A

No; famciclovir is more effective

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20
Q

What is the mechanism of resistance developed by viruses to counteract acyclovir?

A

Loss of viral thymidine kinase

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21
Q

True or False? Acyclovir is effective against latent herpes simplex virus and varicella-zoster virus infections.

A

False; it has no effect on latent forms of these infections

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22
Q

Acyclovir is used to treat herpes infections in what areas/organs?

A

Mucocutaneous (cold sores), genital, herpes simplex virus encephalitis

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23
Q

Why does acyclovir interfere with viral DNA synthesis and not human DNA synthesis?

A

Acyclovir requires monophosphorylation by herpes simplex virus/varicella zoster virus thymidine kinase and formation of a triphosphate form by cellular enzymes

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24
Q

How do viruses develop resistance to acyclovir?

A

Lack of thymidine kinase

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25
Q

How does ganciclovir work?

A

Ganciclovir is a guanosine analog that inhibits viral DNA polymerase

26
Q

Which viral infection is ganciclovir used to treat?

A

Cytomegalovirus (in immunocompromised patients)

27
Q

What four toxicities are associated with ganciclovir use?

A

Leukopenia, neutropenia, thrombocytopenia, and renal toxicity

28
Q

Name the two mechanisms of resistance cytomegalovirus develops against ganciclovir.

A

Mutated viral DNA polymerase, lack of viral kinase

29
Q

Which drug is more toxic, acyclovir or ganciclovir?

A

Ganciclovir

30
Q

What modifications must ganciclovir undergo before becoming active?

A

Formation of a 5’ -monophosphate by either herpes simplex virus/varicella zoster virus thymidine kinase or cytomegalovirus viral kinase and a triphosphate by cellular kinases; this process ensures that it targets viral replication and spares human cells.

31
Q

Foscarnet ____ (does/does not) require activation via phosphorylation by viral kinase.

A

Does not

32
Q

Foscarnet inhibits viral _____ (DNA/RNA) polymerase by binding to the _____ binding site of viral kinase.

A

DNA; pyrophosphate (remember: FOScarnet is a pyroFOSphate analog)

33
Q

For which two infections is foscarnet used?

A

Cytomegalovirus retinitis in the immunocompromised and acyclovir-resistant herpes simplex virus

34
Q

What is the major toxicity of foscarnet?

A

Nephrotoxicity

35
Q

Mutation in which enzyme allows cytomegalovirus or herpes simplex virus to be resistant to foscarnet treatment?

A

DNA polymerase

36
Q

Protease inhibitors end in which suffix?

A

-navir (remember: NAVIR [never] Tease a ProTEASEinhibitor)

37
Q

Name five protease inhibitors.

A

Saquinavir, ritonavir, indinavir, nelfinavir, and amprenavir

38
Q

What are the major toxicities of most protease inhibitors?

A

Gastrointestinal intolerance (nausea, diarrhea), hyperglycemia, and lipid abnormalities

39
Q

What adverse effect is specific to indinavir?

A

Thrombocytopenia

40
Q

Name six nucleoside reverse transcriptase inhibitors.

A

Zidovudine, didanosine, zalcitabine, stavudine, lamivudine, and abacavir (remember: Have YOU DINED[vudine] with my NUCLEAR family?)

41
Q

Name three nonnucleoside reverse transcriptase inhibitors.

A

Nevirapine, Efavirenz, Delavirdine (remember: Never Ever Deliver nucleosides)

42
Q

Reverse transcriptase inhibitors prevent which viral process from occurring?

A

Incorporation of viral DNA into the host genome

43
Q

What toxicities are associated with both nucleoside and nonnucleoside reverse transcriptase inhibitors?

A

Neutropenia, anemia, and peripheral neuropathy

44
Q

Which cause lactic acidosis: nucleoside reverse transcriptase inhibitors or nonnucleoside reverse transcriptase inhibitors?

A

Nucleoside reverse transcriptase inhibitors

45
Q

Which cause rash: nucleoside reverse transcription inhibitors or nonnucleoside reverse transcriptase inhibitors?

A

Nonnucleoside reverse transcriptase inhibitors

46
Q

What nucleoside reverse transcriptase inhibitor used to treat HIV can cause a megaloblastic anemia?

A

Zidovudine

47
Q

What is the name of the combination therapy that is used to treat HIV and that includes a cocktail of protease inhibitors and reverse transcriptase inhibitors?

A

Highly active antiretroviral therapy

48
Q

Which nucleoside reverse transcriptase inhibitor is used for general prophylaxis and during pregnancy to reduce fetal transmission risk?

A

Zidovudine

49
Q

At what point should highly active antiretroviral therapy be initiated in an HIV-positive individual?

A

When the viral load is high or when CD4+ cell count is < 500 cells/mm³

50
Q

In the treatment of HIV infection, what viral process does enfuvirtide inhibit?

A

Fusion

51
Q

What toxicities are associated with enfuvirtide?

A

Hypersensitivity reactions, subcutaneous injection site reaction, increased risk of bacterial pneumonia

52
Q

How does enfuvirtide block entry and replication of viruses?

A

Binding the gp41 subunit, inhibiting the conformational shift required for CD4 cell fusion

53
Q

When is enfuvirtide used clinically?

A

It is added to other antiretroviral drugs when standard regimens have failed

54
Q

How can the bone marrow suppression associated with reverse transcriptase inhibitors be reduced?

A

By treatment with granulocyte-macrophage colony-stimulating factor and erythropoietin

55
Q

What viral process is blocked by enzyme inhibition with protease inhibitors?

A

Maturation of new viruses

56
Q

What are interferons?

A

Endogenous human glycoproteins that induce an anti-viral state in cells

57
Q

What two clinical conditions are treated by interferon therapy?

A

Chronic hepatitis B and C virus infections and Kaposi sarcoma

58
Q

What clinical condition is treated by interferon beta-1a therapy?

A

Multiple sclerosis

59
Q

What clinical condition is treated by interferon γ therapy?

A

Nicotinamide adenine dinucleotide phosphate oxidase deficiency

60
Q

What is the major toxicity of the interferons?

A

Neutropenia

61
Q

In addition to blocking viral DNA and RNA synthesis, interferons also induce what enzyme to encourage viral mRNA degradation?

A

Ribonuclease

USMLE step 1 Rapid Review (6 decks)

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