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4q Pharm Test2 > Antiviral agents > Flashcards

Antiviral agents Flashcards

1
Q

What is a virus?

A
  • contains 1 or more strands of DNA or RNA, often with an outer protein or lipoprotein coat
  • intracellular parasites, so hard to develop drugs that kill viruses without harming the host
  • drugs prevent entry of cituses into cells, block replication of cirus in the cell
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2
Q

3 approaches used for tx & prevention of viral dz

A
  • immunological control (vaccination)
  • stimulation of natural resistance mechanisms in the host
  • chemotherapy
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3
Q

5 stages of viral replication

A
  1. ATTACHMENT & PENETRATION
  2. UNCOATING: protein coat of virus dissolved, liberates viral RNA or DNA
  3. SYNTHESIS OF VIRAL COMPENENTS: virus takes over host cell nucleus and replicates its DNA or RNA, then makes proteins
  4. PACKAGING AND ASSEMBLY OF VIRUS PARTICLE: viral genome maybe encapsulated by viral protein, multiple membranes or no protein
  5. RELEASE OF VIRUS: some are released rapidly, others slowly
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4
Q

HSV causes what?

A

a variety of lesions, including herpetic gingivostamatitis, herpes labialis, herpes zoster and eczema herpeticum

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5
Q

Which 2 drugs are most frequently used to tx herpes

A

oral acyclovir or valcyclovir

IV tx may be needed if herpes infection is severe or life threatening

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6
Q 
Acyclovir (Zovirax) &
Valcyclovir (Valtrex):
what are they?
effective against?
toxicity?
A

synthetic guanosine derivative
very effective against HSV1 & HSV2
low toxicity
Very low toxicity

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7
Q

-cyclovirs : how do they work

A

CYCLOVIRS must be phosphorylated by VIRAL THYMIDINE KINASE to monophosphate compound which can be taken up by cell

PHOSPHORYLATION MORE RAPIE (30-300x) in HERPES INFECTED CELLS than non-HSV infected cells

phosphorylation to triphosphate by host enzymes allows for COMPETITION WITH deoxyGTP

INHIBITS VIRAL DNA POLYMERASE; cases chain termination, which stops DNA replication

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8
Q

acyclovir toxicity and resistance

A

b/c acyclovir is very CONCENTRATED in infected cells, it is virtually NON-TOXIC to normal cells at therapeutic doses

RESISTANCE can develop; viruses may decrease their level of thymidine kinase or alter the DNA polymerase

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9
Q

Acyclovir, Valcyclovir: route of admin/availability

A

active, orally, topically or IV, but oral bioavailability of acyclovir is low

Valcyclovir (Valtrex): a pro-drug with high bioavailability which is given orally & converted to acyclovir->higher serum levels, higher effectiveness

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10
Q

Uses of Acyclovir, Valcyclovir

A

topically: herpes keratitis

orally & applied topically for GENITAL HERPES, increases healing of lesions by 3-5d, decreases duration of pain, new lesions

used chronically to tx recurrent herpes

IV ADMINISTRATION for herpes simplex encephalitis or neonatal herpes

tx of varicella zoster infections (shingles, post-herpetic neuralgia)

prophylaxis in immunocompromised pts post-organ transplant

tx of herpetic gingivostamatitis & recurrent intraoral herpes simplex

longterm suppressive tx recommended for tx of eczema herpeticum

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11
Q

Acyclovir, Valcyclovir side effects

A

MINIMAL w/ORAL use: naseua, diarrhea, headache (rarely)

-high IV dose may case renal tubular obstruction; this is avoided by HYDRATION & slow infusion

SAFE IN PREGNANCY

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12
Q

Tifluridine (Viroptic):
what is it?
used for?
main toxicity?

A

fluorinated thymidine analogue which inhibits viral DNA synthesis

used TOPICALLY for HERPES infections RESISTANT TO ACYCLOVIR

main toxicity: visual haze & discomfort

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13
Q 
Famciclovir (Famvir): 
use 
mechanism/conversion
excreted by?
(C) side effects
A
  • converted in vitro to PENCICLOVIR (Denavir)
  • used for management of acute HERPES ZOSTER (SHINGLES) or recurrent genital herpes
  • phosphorylated by VIRAL THYMIDINE KINASE like acyclovir
  • excreted by kidney, renal fxn important
  • nausea, HA & diarrhea common
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14
Q

Docosanol (Abreva):
how does it work?
use?
SEs?

A
  • inhibits fusion btwn host cell plasma membrane & herpes simplex virus (HSV) envelope; prevents entry of virus into the cell
  • used TOPICALLY for COLD SORES
  • available OTC
  • may irritate skin or cause HA
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15
Q 
Ganciclovir Sodium (Cytovene);
Valganciclovir (Valcyte)
A

synthetic analogues of guanosine, similar to acyclovir, but slightly more toxic

active against CMV & herpes

PHOSPHORYLATED by thymidine kinase in cells infected w/HERPES
& by VIRAL PROTEIN KINASE PHOSPHOTRANSTERASE IN CMV INFECTED CELLS

once phosphorylated, inhibits DNA polymerase, suppresses DNA chain elongation & inhibits CMV replication

VALGANCICLOVIR: prodrug w/much higher oral absorption than ganciclovir

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16
Q

Uses of valganciclovir, ganciclovir

A

VALGANCICLOVIR used ORALLY for prophylaxis & therapy of CMV infections

used prophylactically in organ transplant pts to reduce risk of developing CMV, herpes

IV to tx life or sight threatening CMV infections

OCULAR IMPLANT which lasts 5-8mos is available for tx of CMV retinitis

17
Q

Valganciclovir, ganciclovir toxicity

A

NEUTROPENIA: mainly when given IV, esp. when COMBINED WITH ZIDOVUDINE

other adverse effects: fever, rash, phlebitis, confusion, HA, coma, seizures and abnormal LFTs

18
Q 
Cidofovir (Vistide)
used to tx (2)
structure/mechanism
unique feature
side effects
A

used for CMV RETINITIS & HERPES infections

cytosine analogue, inhibits viral DNA polymerase

doesn’t need intracellular activation=USEFUL AGAINST STRAINS RESISTNAT TO GANCICLOVIR

may cause renal tubular necrosis (prevented w/hydration & probenicid)

SEs: oclar hypotonia, uveitis & probenacid-related hypersensitivity

19
Q

Foscarnet (Foscavir)

A

directly inhibits HSV DNA POLYMERASE & HIV reverse trascriptase

USED TO TX ACYCLOVIR-RESISTANT HERPES infections & CMV RETINITIS (often in aids)

only IV, sometime w/ganciclovir

eliminated by kidney so toxicity includes RENAL INSUFFICIENCY
hypo or hypercalcemai when combined w/pentamidine
malaise, N/V, fatigue, HA, CNS disturbances, seizures, hallucinations, genital ulcers may occur from high levels in urine, esp men

20
Q

Fomivirsen (Vitravene): how does it work, indication, SEs

A

-ANTISENSE COMPOUND complementary to a mRNA sequence in CMV; inhibits protein synthesis & viral replication
admin by INTRAVITREAL injection
-used for tx of CMV retinitis in AIDS pts who failed other therapy
-can be used w/either foscarnet of ganciclovir

SEs: OCULAR INFLAMMATION & VISUAL IMPAIRMENT

21
Q

Oseltamivir (Tamiflu): type of med, action, administration, activation, excretion

A

NEURAMINIDASE INHIBITOR active against both influenza A & B

INHIBIT RELEASE OF VIRUS FROM INFECTED CELLS

oral admin

activated in gut & liver, excreted by the kidney; also used for tx of bird flu

some forms seasonal H1N1 have become resistant

22
Q

Zanamivir (Relenza): type of med, action, administration, activation, excretion

A
  • NEUROAMINIDASE INHIBITORS active against influenza A & B
  • INHIBIT RELEASE OF VIRUS FROM INFECTED CELLS
  • give INTRANASALLY or by ORAL INHALER b/c it is not absorbed orally
  • tx is initiated 35-48h after onset of symptoms, & lasts for 5 days
23
Q

adverse effects of Zanamivir (3)

A

may WORSEN RESPIRATORY FXN in patients with chronic obstructive pulmonary dz
or
cause BRONCHOSPASM in asthmatics

causes nasal & throat discomfort

24
Q

adverse effects of Oseltamivir (2)

A

NAUSEA & VOMITING, reduced if taken with food

25
Q

Amantidine, Rimantadine
how do they work?
use?

A

block UNCOATING of virus, inhibiting release of viral nucleic acids into the cell cytoplasm
-well absorbed orally
prevents/tx INFLUENZE TYPE A1 (ASIAN) in HIGH RISK pts
PROPHYLACTIC use reduces incidence & severity of sxs
may decrease duration for sxs by 1-2d

rarely used since development of oseltamacir

26
Q

Amantadine, Rimantadine: side effects

amantadine?

rimantadine”

both?

A

amantadine increases DOPAMINE RELEASE & may cause CNS EFFECTS: HALLUCINATIONS, confusion, anxiety, irritability, anorexia

rimantadine: doesn’t cross BBB & doesn’t have CNS effects
both: NAUSEUA, dizziness, occasional vomiting

4q Pharm Test2 (7 decks)

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