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Antibiotic > Anti-viral > Flashcards

Anti-viral Flashcards

1
Q

Anti-viral for CMV

A

Ganciclovir

Valganciclovir

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2
Q

Anti-viral for HSV, VZV

A

Acyclovir

Valacyclovir

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3
Q

Mechanism of Action for

acyclovir and valacyclovir

A

Acyclovir is an acyclic guanosine analog.
it is approximately 10 times more potent against HSV-1 and HSV-2 than against VZV.

Acyclovir requires three phosphorylation steps for activation. It is converted first to the monophosphate derivative by the virus specified thymidine kinase and then to the di- and triphosphate compounds by host cell enzymes.

Acyclovir triphosphate inhibits viral DNA synthesis by two mechanisms: competition with deoxyGTP for the viral DNA polymerase, resulting in binding to the DNA template as an irreversible complex;
and
chain termination following incorporation into the viral DNA

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4
Q

Mechanism of action for Ganciclovir and valganciclovir

A

Ganciclovir is an acyclic guanosine analog that requires activation by triphosphorylation before inhibiting the viral DNA polymerase. (to become drug triphosphate)
Thus interfering with Viral DNA synthesis.

Acts as a competitive substrate for DNA polymerase leading to chain termination following its incorporation into viral DNA.

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5
Q

Mode of administration of Anti-HSV

A

acyclovir ——– Oral, IV, topical

valacyclovir = oral

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6
Q

Mode of administration of Anti-CMV

A

ganciclovir ———-IV , intravitreal

Valganciclovir——– Oral

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7
Q

Absorption for acyclovir

A

low (15-20%)

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8
Q

absorption for valacyclovir

A

54-70%

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9
Q

absorption ganciclovir

A

0%

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10
Q

absorption valganciclovir

A

60% recommended to take with food

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11
Q

Distribution of acyclovir

A

diffuse readily to all tissue

CSF 20-30%

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12
Q

Distribution of valacyclovir

A

CSF ~50%

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13
Q

Distribution of ganciclovir

A

CSF ~50%

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14
Q

Acyclovir metabolism

A

hepatic

thru oxidation and hydroxylation

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15
Q

valacyclovir metabolism

A

hepatic and intestinal hydrolysis

to acyclovir

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16
Q

ganciclovir metabolism

A

0

17
Q

valganciclovir metabolism

A

rapidly hydrolyzed in the intestinal wall and liver to ganciclovir

18
Q

Elimination of acyclovir , valacyclovir , ganciclovir and valganciclovir

A

Renal:

glomerular filtration and active secretion.

19
Q

half life acyclovir

A

2.5-3.3h

20
Q

half life valacyclovir

A

serum x5 more than acyclovir

2.5-3.3h

21
Q

half life ganciclovir

A

4h

can be removed by hemodialysis

22
Q

half life valganciclovir

A

4h

can be removed by hemodialysis

23
Q

Clinical application of acycovir and valacyclovir

A

Genital herpes, varicella and zooster treatment, herpes encephalitis.

Prophylactic use of acyclovir in patients on immunosuppressants undergoing transplant or radiation therapy, who are all at risk of infection from reactivation of the virus frequent recurrence of HSV infection of genitalia

24
Q

Clinical application of Ganciclovir and valganciclovir

A

Ganciclovir:

  1. for systemic CMV infection in HIV and immunocompromised patients.
  2. As maintenance therapy for Cytomegalovirus (CMV) retinitis in immunocompetent patients

Valganciclovir
1. Valganciclovir has recently been shown to reduce transmission of genital HSV

25
Q

Side effect of acyclovir and valacyclovir

A
  1. GIT-related symptoms
  2. Renal dysfunction from IV administration (due to deposition of drug in renal tubules) (Caution: give drug slowly (over 1 hr or more), and ensure adequate hydration).
  3. CNS-related:
    i. headache
    ii. encephalopathy – tremors, with IV doses
  4. Hematologic
    i. thrombotic thrombocytopenic purpura (TTP);
    ii. hemolytic uremic syndrome (in immunocompromised patients given valacyclovir).

Non-teratogenic compared to ganciclovir

26
Q

Side effect of ganciclovir and alganciclovir

A
  1. Bone marrow suppression, particularly neutropenia (less with the oral route)
  2. GIT-related: diarrhoea, nausea, vomiting
  3. irreversible aspermatogenesis at high doses
  4. potential mutagenicity and carcinogenesis;
  5. teratogenicity and possible embryotoxicity.
    Women are to avoid pregnancy until at least 90 days
    after the end of treatment.
  6. CNS-related: headache

More toxic than acyclovir

27
Q

DDI for acyclovir and valacyclovir

A

nephrotoxic agents

Probenecid and cimetidine decrease acyclovir clearance and increase exposure.

28
Q

DDI for gancicloir and valgancicloir

A

Imipenem

  • enhance the ADR effect of imipenem and increase risk of seizure

NNRTI

  • enhance the ADR effect of reverse transcriptase inhibitors (nucleoside)
  • hematologic toxicity is of specific concern.

High fat meal
- increase AUC by 30%

Antibiotic (21 decks)

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