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Drug Mechanisms > Antivirals > Flashcards

Antivirals Flashcards

1
Q

Drug used in the treatment of Herpes Simplex Virus and Varicella Zoster Virus

A

Acyclovir

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2
Q

Mechanism of action for Acyclovir

A

It inhibits DNA synthesis in two ways. It competitively inhibits deoxyGTP which cause DNA template strand to bind to an inactive complex. It can also incorporate itself in the DNA strand and cause chain termination.

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3
Q

Toxicity of Acyclovir

A

Nausea, vomiting, and headache

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4
Q

Mechanism of resistance to Acyclovir

A

Alteration of thymidine kinase or DNA polymerase

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5
Q

Which drugs don’t require activation by thymidine kinase?

A

Cidofovir, foscarnet, and trifluridine

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6
Q

What is the only anti-HSV IV drug available?

A

Acyclovir

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7
Q

What is required to activate Acyclovir?

A

Three phosphorylation steps: first converted to monophosphate derivative and then to di- and tri- derivatives by host’s cellular enzymes

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8
Q

What 3 drugs are used to treat Cytomegalovirus?

A

Ganciclovir, Cidofovir, and Foscarnet

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9
Q

Mechanism of action of Ganciclovir

A

Competitively inhibits DNA polymerase and causes termination of the growing DNA strand

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10
Q

Mechanism of action of Cidofovir

A

Acts as a potent inhibitor and alternative substrate for viral DNA polymerase

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11
Q

Mechanism of action of Foscarnet

A

Inhibits viral DNA polymerase, RNA polymerase, and HIV reverse transcriptase without activation by phosphorylation. It blocks the pyrophosphate binding site of these enzymes and inhibits cleavage of pyrophosphate from deoxynucleotide triphosphates

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12
Q

Mechanism of resistance to Ganciclovir

A

Mutations in UL97 which activates the drug and UL54 which results in mutant DNA polymerase

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13
Q

Toxicity to Ganciclovir

A

Myelosuppression and Retinal detachment (in patients with CMV retinitis)

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14
Q

How many times greater is the activity of Ganciclovir against CMV compared to Acyclovir?

A

100 times greater

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15
Q

Toxicity to Cidofovir

A

Dose-dependent nephrotoxicity and decreased intraocular pressure

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16
Q

What type of analog is cidofovir?

A

Cytosine analog

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17
Q

What activates Cidofovir?

A

Human cell kinases

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18
Q

Toxicity of foscarnet

A

Nephrotoxicity, anemia, and CNS toxicity (headache, hallucinations, and seizures)

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19
Q

What type of analog is foscarnet?

A

It is an inorganic pyrophosphate analog

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20
Q

What viruses does foscarnet act against in-vivo?

A

HSV, VZV, CMV, and HIV-1

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21
Q

What two drugs are Nucleoside/Nucleotide Reverse Transcriptase Inhibitors?

A

Zidovudine and Tenofovir

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22
Q

What drug is a Non-Nucleoside/Nucleotide Reverse Transcriptase Inhibitor?

A

Nevirapine

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23
Q

Mechanism of action of Zidovudine and Tenofovir?

A

Binds to the DNA polymerase catalytic site on the reverse transcriptase enzyme which competitively inhibits DNA polymerase activity, and can be incorporated into the viral DNA chain causing termination

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24
Q

Mechanism of resistance to Zidovudine and Tenofovir?

A

viral mutations and there is cross-resistance between NRTIs

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25
Q

Toxicity to Zidovudine and Tenofovir

A

Lactic acidemia and hepatomegaly

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26
Q

What is important about NRTIs in pregnancy?

A

Zidovudine is used to prevent vertical transmission from mother to child. If the mother is already in labor, Zidovudine can still be used.

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27
Q

What activates NRTIs?

A

human cell kinases in the cytoplasm

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28
Q

Mechanism of action for Non-Nucleoside/Nucleotide Reverse Transcriptase Inhibitors

A

Binds directly to sites on the reverse transcriptase enzyme resulting in allosteric inhibition of RNA and DNA-dependent DNA polymerase activities

29
Q

Mechanism of resistance to Non-Nucleoside/Nucleotide Reverse Transcriptase Inhibitors

A

Viral mutations. No cross-resistance between NRTIs and NNRTIs or protease inhibitors

30
Q

Toxicity to Non-Nucleoside/Nucleotide Reverse Transcriptase Inhibitors

A

GI intolerance and skin rash

31
Q

Do NNRTIs need to be activated?

A

No

32
Q

What is Nevirapine used for in pregnant women?

A

It is used to prevent transmission of HIV from mother to child via breastfeeding

33
Q

What can occur within the first 6 weeks of treatment with Nevirapine?

A

Fulminant hepatitis

34
Q

Which drugs are inhibitors of p450 CYP3A4?

A

Nevirapine, Ritonavir (protease inhibitors), Telaprevir, Boceprevir, Terbinafine, and Simeprevir

35
Q

Which drugs are inducers of p450 CYP3A4?

A

Griseofulvin and NNRTIs

36
Q

What drug class is ritonavir?

A

Protease inhibitor

37
Q

Mechanism of action for ritonavir

A

Inhibits the protease enzyme which inhibits cleavage of the gag-pol enzyme which results in the production of immature, non-infectious viral particles

38
Q

Mechanism of resistance to ritonavir

A

genotypic mutations (usually in monotherapy). Cross-resistance between protease inhibitors and appears to require a minimum of 4 substitutions in the gene

39
Q

Toxicity to ritonavir

A

Lipodystrophy, increase in triglyceride and LDL levels, glucose intolerance, and insulin resistance

40
Q

What types of HIV does ritonavir inhibit?

A

HIV-1 and HIV-2

41
Q

What drug class is Enfuvirtide?

A

Fusion inhibitor

42
Q

Mechanism of action for Enfuvirtide

A

blocks entry into the cell by binding to gp41 subunit on the viral envelope glycoprotein preventing conformational changes required for fusion of the virus

43
Q

Mechanism of resistance to Enfuvirtide

A

It’s still being studied. There is no cross-resistance between enfuvirtide and other antiretroviral drugs

44
Q

Toxicity to Enfuvirtide

A

Injection site reactions and hypersensitivity reactions

45
Q

Structure of Enfuvirtide

A

synthetic-amino-acid peptide

46
Q

Route of administration for Enfuvirtide

A

Subcutaneous injection

47
Q

What drug class is Maraviroc?

A

CCR5 Antagonist

48
Q

Mechanism of action for Maraviroc

A

Binds to and blocks CCR5 on CD4 cells blocking HIV from invading CD4 cells. This only works in patients with CCR5-tropic disease so a patient must undergo testing/screening to determine tropism of their HIV infection before using Maraviroc

49
Q

Toxicity to Maraviroc

A

Hepatotoxicity, cardiovascular events, increased risk of infections and malignancy

50
Q

What two receptors does HIV use to invade CD4 cells?

A

CCR5 and CXCR4

51
Q

What drug class is Raltegravir?

A

Integrase Strand Transfer Inhibitors

52
Q

Mechanism of action for Raltegravir

A

Inhibits the integrase enzyme preventing viral DNA from integrating with cellular DNA

53
Q

Mechanism of resistance to Raltegravir

A

mutations in the integrase enzyme

54
Q

Toxicity to Raltegravir

A

Increased serum creatine kinase, myopathy, rhabdomyolysis

55
Q

What is Raltegravir used for?

A

HIV-1 strains that are resistant to other antiretroviral drugs

56
Q

What drug combination is used for Pre-Exposure Prophylaxis for HIV

A

Tenofovir and Emtricitabine

57
Q

How can a patient become resistant to Tenofivir and Emtricitabine?

A

If they take the drugs and actually have the HIV infection

58
Q

What is the treatment option for Post-Exposure Prophylaxis for HIV?

A

3 or more active antiretroviral drugs

59
Q

What drugs are used in antiretroviral therapy?

A

Zidovudine, Tenofovir, Nevirapine, Ritonavir, Enfuviratine, Maraviroc, and Raltegravir

60
Q

What drugs are used in Anti-hepatitis therapy?

A

Adefovir, Interferon Alfa, Ribavirin, Telaprevir + Boceprevir, Simeprevir, Sofosbuvir, and Sofosbuvir + Ledipasvir

61
Q

Mechanism of action of Adefovir

A

Phosphorylated by cellular kinases to the active metabolite. Once activated, it competitively inhibits DNA polymerase and results in chain termination after incorporation into the viral DNA

62
Q

Toxicity of Adefovir

A

Dose-dependent nephrotoxicity, Lactic acidosis, and hepatomegaly

63
Q

Mechanism of action of Interferon alpha

A

Binds to specific membrane receptors on the cell surface and initiate enzyme induction, suppression of cell proliferation, immunomodulatory activities, and inhibition of viral replication. Following binding to receptors, IFNs activate the JAK-STAT signal-transduction pathway and leads to nuclear translocation of a cellular protein complex that binds to genes containing and IFN-specific response

64
Q

Mechanism of resistance to Interferon alpha

A

blocking production or activity of selected IFN-inducible antiviral proteins

65
Q

Toxicity to Interferon alpha

A

Flu-like syndrome, thrombocytopenia, anemia, hypotension, neuropsychiatric, and should not be administered during pregnancy

66
Q

What can interferon alpha do to the immune system?

A

Modify it

67
Q

What products have longer half-lives, slower clearance, and steadier serum concentrations allowing for less frequent dosing?

A

Pegylated products

68
Q

Mechanism of action for Ribavirin

A

Interferes with the synthesis of guanosine triphosphate, inhibits capping of viral mRNA, and inhibits viral RNA-dependent RNA polymerase

69
Q

Toxicity to Ribavirin

A

Hemolytic anemia, depression, and shouldn’t be administered during pregnancy

Drug Mechanisms (9 decks)

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