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D&D Unit 4 > Anti-viral Agents (complete) > Flashcards

Anti-viral Agents (complete) Flashcards

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1
Q

What are the different classifications of anti-viral agents for flu?

A

1) Inhibition of viral neuraminidase

2) Inhibition of uncoating

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2
Q

What are the different classifications of anti-viral agents for herpes?

A

1) Inhibition of viral genome replication (viral DNA polymerase)
2) Inhibitors of viral penetration

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3
Q

What are the different classifications of anti-viral agents for RSV?

A

Only one type

1) Purine nucleoside analogy

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4
Q

What are the different classifications of anti-viral agents for cytomegalovirus?

A

1) Inhibition of viral DNA polymerase
2) Ganciclovir/Valganciclovir
3) Foscarnet

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5
Q

What are the two anti-virals for flu that are neuraminidase inhibitors?

A

1) Oseltamivir

2) Zanamivir

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6
Q

Describe the mechanism of action for neuraminidase inhibitors of flu

A
  • Works against influenza A and B
  • If NA activity is blocked virions clump at cell surface => decrease viral infectivity
  • NA inhibition impairs viral penetration through mucin secretions => decreased infection of other respiratory epithelial cells
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7
Q

Describe flu’s resistance to NA inhibitors

A
  • It’s rare

- If it does happen, through mutations in neuraminidase or hemagluttinin

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8
Q

How is oseltamivir absorbed?

A

PO

  • a prodrug
  • 80% bioavailability
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9
Q

How is zanamivir absorbed?

A

Via inhalation

Goal: to deliver to respiratory tract

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10
Q

How is oseltamivir eliminated?

A
  • kidneys (glomer filtration-tubular secretion)

- Dosage must be changed if pt has renal probs

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11
Q

How is zanamivir eliminated?

A
  • 10-20% of inhaled dose is absorbed

- Remainder excreted via urine

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12
Q

Describe the clinical use of oseltamivir

A 
Who:
Children (>1yo) and adults)
When: 
Start w/in 48hrs of symptoms
Purpose:
decreases severity and duration of flu

Can be given prophylactically => 70-90% effective in prevention

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13
Q

Describe the clinical use of zanamivir

A 
Who:
Those >7yo
When:
Start w/in 2 days of symptoms
Purpose:
Shorten duration -- decrease lower respiratory tract complications
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14
Q

What are the adverse rxns associated with oseltamivir?

A
  • Nausea and vomiting
  • Abdominal pain

Decreased if taken w/food

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15
Q

What are the adverse rxns associated with zanamivir?

A

Cough, brochospasm

CAN BE SEVERE

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16
Q

What are the two anti-virals for flu that inhibit uncoating?

A

1) Amantadine

2) Rimantadine

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17
Q

Describe the mechanism of action for uncoating inhibitors for flu

A
  • Blocks virally-encoded H+ ion channel —AKA: M2 protein

- Prevents the pH change necessary for uncoating!

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18
Q

Describe flu’s resistance to uncoating inhibitors

A
  • Mutations in transmembrane domains of M2 proton channel

- Can no longer block that channel

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19
Q

How are amantadine/rimantadine absorbed?

A

effective PO

ACCUMULATES in LUNGS

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20
Q

How is amantadine excreted?

A

Unchanged in urine

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21
Q

How is rimantadine excreted? Discuss the limits of its distribution

A
  • Hepatic elimination

- Increased protein-bind limits distribution to CNS

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22
Q

Describe the clinical uses of amantadine and rimantadine. Why is use currently limited?

A
  • Used for prophylaxis and tx of influenza A

- Limited use: b/c of RESISTANCE

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23
Q

What are the adverse rxns associated with amantadine?

A
  • Insomnia
  • Concentration difficulty
  • Lightheadedness/dizziness
  • Headache
  • GI upset
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24
Q

What are the adverse rxns associated with rimantadine?

A

Better than amantadine but similar effects

CNS probs not as bad b/c of decreased CNS penetration

  • Insomnia
  • Concentration difficulty
  • Lightheadedness/dizziness
  • Headache
  • GI upset
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25
Describe the mechanism of action of acyclovir and its analogs
- Diffuse into cell => triphosphorylated by intracellular kinases - The Acyclo triphosphate inhibits viral DNA polymerase (more sensitive than human DNA poly) - A DNA chain terminator w/ irreversible binding btwn DNA poly and terminated chain
26
Describe the selectively toxic effects of acyclovir in herpes tx
- 1st phosphorylation step by herpes-encoded thymidine kinase - Only occurs in infected cells
27
Describe viral resistance to acyclovir and its analogs
MOST COMMON: - Reudction/loss of expression of viral thymidine kinase Also: - altered TK substrate specificity - altered affinity of viral DNA poly activity Resistance happens mainly in *immunosuppressed pts* receiving extended acyclovir tx regimens
28
How is acyclovir absorbed?
poor PO - PO, topically, IV
29
How is valacyclovir absorbed?
- valyl ester prodrug of acyclovir | - 80-90% bioavailability
30
How is penciclovir absorbed?
- Topical ONLY | - poor PO
31
How is famciclovir absorbed?
- Diacetyl ester of penciclovir | - 70% bioavailability
32
Describe the distribution of acyclovir and its analogs
Cross cell membrane => phosphorylated => 'trapped' intracellularly
33
How are acyclovir and penciclovir eliminated?
- Kidneys | - t1/2s significantly prolong w/ kidney probs or in neonates
34
Describe the clinical use of acyclovir in primary infections of HSV 1&2
- Beneficial if given in first 48-72hrs - Oral acyclovir => 3-5doses/day for 7-10 days - Oral famiciclovir (tid) or valacyclovir (bid) for 7-10 days - Topical acyclovir/penciclovir requires frequent administration
35
Describe the clinical use of acyclovir in recurrent infections of HSV 1&2
- Treatment considerations: severity, recurrence fq, cost, pt preference, partner uninfected or not (may require chronic tx) - Ranges from no tx to epsidodic tx to chronic suppressive tx based on the above
36
Describe the clinical use of acyclovir in treatment of primary infection of varicella zoster (aka chicken pox)
- No tx for kids <12yo - Acyclovir (qid for 5d) for adults -- uncomplicated - Acyclovir IV (tid for 7d) if immunosuppressed or severe complications
37
Describe the clinical use of acyclovir in treatment of recurrent infection of varicella zoster (aka shingles)
- More beneficial if started in first 72 hrs - Oral acyc (3-5 doses/day) => 7d - IV for immunosuppressed
38
Describe the adverse rxns associated with acyclovir and its analogs
- Tolerated well PO: only headache, n/v - IV route or valacyclovir: CNS effects (confusion, hallucinations, seizures) - Renal tox w/ IV --- decreases w/ hydration - Preg cat B
39
Describe the mechanism of action of docosanol
- Long chain saturated alcohol => inhibits replication of lipid-enveloped viruses - Prevents fusion btwn cellular and viral envelope membranes => blocks viral entry into cell!!
40
Describe the clinical uses of docosanol
- Available over-the-counter (ABREVA) - Topical tx: 5xday - Must begin w/in 12 hrs of symptoms
41
Describe the adverse rxns associated with docosanol
Well-tolerated
42
Describe the mechanism of action of ganciclovir and valganciclovir
- phosphorylated to Gan-MP by viral kinase (UL97) => then active Gan-TP by host kinases - Gan-TP incorporated into replicating viral DNA => slows and ceases DNA elongation
43
Describe how cytomegalovirus develops resistance to ganciclovir and valganciclovir
- Mutations in activating kinase (UL97) | - Mutations in viral DNA poly target (UL54)
44
How is ganciclovir absorbed?
- poor PO, still given PO | - given IV or intraocularly
45
How is valganciclovir absorbed?
- Valyl ester prodrug of ganciclovir - Has 60% bioavailability PO
46
How is foscarnet absorbed?
IV only - poor oral bioavailability and GI intolerance
47
How is cidofovir absorbed?
IV only - nucleotide analog
48
How is ganciclovir eliminated?
Kidney - Filtration and secretion
49
How is foscarnet eliminated?
Kidney
50
How is cidofovir eliminated?
- Tubular secretion An active metabolite w/ long intracellular t1/2 Can be admin'd w/ probenecid to block secretion and decrease nephrotoxicity
51
Describe the clinical use of ganciclovir in treatment of cytomegalovirus
- Induction/maintenance tx of CMV retinitis in immunocompromised pts - Used to prevent CMV in transplant pts Given IV or ocular implant
52
Describe the clinical use of valganciclovir in treatment of cytomegalovirus
- Treats CMV retinitis PO => bid for 21d, then once/d
53
Describe the clinical use of foscarnet in treatment of cytomegalovirus
- Treats CMV retinitis in pts w/ AIDS IV => q8-12h for 14-21d, then once/d
54
Describe the clinical use of cidofovir in treatment of cytomegalovirus
CMV retinitis if no response to ganciclovir or foscarnet IV => once/wk x 2, then q2weeks
55
Describe the adverse rxns associated w/ ganciclovir and valganciclovir
- Myelosuppression (esp. IV route) | - Also nausea, diarrheam fever, rash, insomnia, headache
56
Describe the adverse rxns associated w/ foscarnet
RENAL IMPAIRMENT!! => hypocalcemia CNS abnormalities (HA, tremor, seizures, hallucinations)
57
Describe the adverse rxns associated w/ cidofovir
Proximal tubular nephrotoxicity (dose dependent) Neutropenia, uveitis
58
Describe the mechanism of action of ribavirin
- purine nucleoside analog - inhibits DNA & RNA viruses - MOA not completely understood - Converted to ribavirin-TP by *cellular* kinases => interferes w/ GTP & NA synthesis - Inhibits GTP-dependent 5' capping of viral mRNA - May increase mutagenesis rates => viral suicide
59
Describe how RSV develops resistance to ribavirin
No resistance observed to date
60
How is ribavirin absorbed?
PO - Bioavailability (45-64%) goes up w/ fatty meals
61
How is ribavirin eliminated?
Hepatic metabolism => renal excretion of unchanged drug
62
Describe the half-life variation of ribavirin
Varies w/ route of admin - Inhalation (children): 6-11 hrs - Oral for hep C (adults): initial plasma t1/2 = 43hrs --- steady state >150 hrs
63
Describe the clinical uses of ribavirin in treatment of RSV
- RSV brochiolitis and pneumonia in hospitalized kids => inhalation - RSV infection (w/IVIG) in BM transplant and other immunocompromised pts - Also used in hep C => PO
64
Describe the adverse rxns associated w/ ribavirin when administered via inhalation
- Well-tolerated --- can cause conjunctival/bronchial irritation - Acute deterioration of resp function in pts w/ brochospastic lung disease - high incidence of headache/conjunctivits in HC workers Preg category X!!!
65
Describe the adverse rxns associated w/ ribavirin when administered via PO
- oral-systemic => used for Hep C - Hemolytic anemia!! - When given w/ interferon (another Hep C drug) => more cough, pruritus, rash
66
What is palivizumab?
Humanized monoclonal AB to RSV F glycoprotein
67
When is palivizumab used?
RSV immunoprophylaxis in infants w/ congenital heart disease
68
How is palivizumab administered?
- Given IM monthly - Max of 5 doses Before beginning of RSV season (usually Nov)
69
What are some issues associated w/ palivizumab?
Expensive --- benefits vary among risk groups - Generally well-tolerated w/ rare severe hypersensitivity rxn (<1 per 100K)

D&D Unit 4 (18 decks)

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