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GI Pharm > Drugs for HCV and HBV > Flashcards

Drugs for HCV and HBV Flashcards

1
Q

What is the MOA of Tenofovir disoproxil

A

Pro-drug for tenofovir. Nucleotide analog of AMP - gets phosphorylated = diphosphate form inhibits HBV polymerase and produces chain termination

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2
Q

What is the MOA of Entecavir

A
  • guanosine nucleotide analog

- triphosphate form inhibits HBV polymerase

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3
Q

What is the MOA of adefovir

A
  • AMP analong

- diphosphate form incorportated into viral DNA producing chain termination

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4
Q

What is MOA of lamivudine and emtricitabine

A

L-isomer of cytosine

- triphosphate form inhibits HBV polymerase

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5
Q

What do you need to worry about anti-viral resistance for HBV infxns

A
  • tends to be structure specific
  • adefovir and tenofovir have acyclic phosphonate structure
  • entecavir has a d-cyclopentane
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6
Q

What are some general characteristics for HBV anti-viral drugs?

A
  1. little or no CYP interaction
  2. renal function in important - dose reduction in renal dysfuntion.
  3. Entecavir has longest half life
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7
Q

How is bioavailability affected in HBV drugs?

A
  1. Tenofovir – take w/ high fat meal
  2. Entecavir - food delays absorption
  3. rest - food has no substantial effect
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8
Q

What are ADEs for Tenofovir

A
  1. Rental toxicity - so test creatinine and BUN, avoid concurrent usage of nephrotoxic agents like NSAIDS
  2. Bone pain, bone fractures, pain in extremities, muscle pain –> Osteoporosis -> give Ca and Vit D supplements
  3. Hepatic toxicity - lactic acidosis, steatosis. Check LFTs. This is common in W, obesity, alcoholism, prolonged drug exposure
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9
Q

What is thought to be the mechanism of the renal and hepatic toxicity for anti-virals

A

inhibits mitochondrial DNA polymerase

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10
Q

When you have a co-infxn of HBV and HIV, what should you give the patient?

A
  • tenofovir, entecavir = truvada

- don’t use lamivudine and emtricitabine

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11
Q

ADS for adefovir, Lamivudine, entecavir

A
  1. adefovir - renal toxicity and hepatic
  2. Lamivudine - renal tox
  3. entecavir - renal and hepatic tox
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12
Q

What is the MOA of interferons

A

Antiviral, antiproliferative, and immunomodulatory.

  • binds to receptor, activates TK (Jak/STAT) –> produces several IFN stimulated enzymes.
    1. Endoribonucleases cleave ssRNA
    2. Inibitory effects upon dsRNA
    3. inhibition of viral penetration, uncoating, assemly, and release
    4. enhances lytic effects of cytotoxic T cells
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13
Q

IFN ADEs

A
  1. Acute FLS following injection - can treat w/ antipyretics
  2. Dose limiting Neurophysc issues, myelosuppression w/ granulocytopenia, and thrombocytopenia. Hepatotoxic - checks LFTs.
  3. Monitor thyroid function and give appriopriate treatments for symptoms and continue antiviral treatment.
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14
Q

MOA of ribavirin

A
  1. enhanced host T cell immune clearance of HCV
  2. inhibit IMPDH w/ depletion of pools of GTP (essential substrate for viral RNA synthesis)
  3. direct inhibition of HCV replication
  4. RNA virus mutagenesis drives HCV to error
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15
Q

What effect does ribavirin have on the clinical dz of HCV

A

transiently reduces HCV RNA but normalizes ALT; syngerizes w/ IFN to decrease risk of viral relapse

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16
Q

ADE of ribavirin

A

Hemolytic anemia, fatal/nonfatal MI, difficulty breathing, male mediated tertaogenicity

17
Q

bioavability of ribavirin

A
  • increased w/ high fat meal
  • very large Vd and long half life - extensive uptake into cells
  • NO CYP action
18
Q

MOA of Telaprevir and Boceprevir

A

NS3/4A serine protease inhibitors

19
Q

Bioavailability of Telaprevir and Boceprevir

A
  1. less effective in AA
  2. produces benefit in naive pts and those relapsing on combo therapy
  3. Take w/ food ( high fat for telaprevir)
  4. Hepatic metabolism w/ elimination in stool
  5. extensively bind plasma proteins
20
Q

What is the ADE of telaprevir

A
  1. fatigue, anemia, nausea

2. BBW for serious rash

21
Q

ADE of Boceprevir

A

fatigue, anemia, nausea

22
Q

Pharm characteristics for Telaprevir and Boceprevir

A
  1. Telaprevir : substrate and inhibitor for CYP3A4 and Pgp
  2. Boceprevir : metabolized by aldoketoreductase and CYP3A4/PgP
    * co admin w/ strong CYP3A4 inducers or w/ drugs reliant on CYP3A4 or Pgp contraindicated.

GI Pharm (7 decks)

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