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Infection > Antivirals > Flashcards

Antivirals Flashcards

1
Q

Are antivirals virustatic or virucidal?

A

•All are virustatic, none are virucidal

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2
Q

Why are there limited viral proteins that are potential targets for antiviral drugs?

A

As viruses utilise host cell enzymes in order to replicate

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3
Q

What are the targets of antivirals?

A

Stages of the viral replication

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4
Q

What are most antivirals composed of?

A

Most antivirals are nucleoside anologues, therefore inhibiting nucleic acid synthesis

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5
Q

What are the stages of antiviral drug therapy?

A

Receptor binding

Cell entry

Uncoating

Nucleic acid synthesis, integration (retroviruses), transcription, viral protein synthesis

Assembly

Release

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6
Q

When might antiviral treatment begin?

A

Prophylaxis

Pre-emptive therapy (when evidence of infection, but before symptoms are apparent)

Overt disease

Suppressive therapy - (to keep viral replication below the rate that causes tissue damage in asymptomatic infected patient)

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7
Q

Why might maintenance treatment be needed after successful treatment of an episode of overt infection?

A

Antivirals do not eradicte virus from latently infected cells (e.g herpes viruses)

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8
Q

What viral infections are antivirals used for?

A

Herpes viruses: HSV 1 and 2, VZV, CMV (aciclovir, famciclovir)

HIV

Hepatitis: Hep B and Hep C (tenofovir)

Respiratory: Influenza - oseltamivir, zanamivir, respiratory syncytial virus (RSV - ribavarin)

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9
Q

When are antivirals given to someone with herpes simplex?

A

Mucocutaneous: oral, genital, eye, skin

Encephalitis

Immunocompromised - any site

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10
Q

When are antivirals given to someonewith chickenpox?

A

In those at icnreased risk of complications…

neonate

Immunocompromised

Pregnant

Immunocompetent adult - only begun within 24 hours of onset of rash

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11
Q

What is the specification before giving antivirals to someone with shingles?

A

Only decreases post-herpetic neuralgia in the immunocompetent patient if begun within 72 hours of onset of symptoms

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12
Q

What are the antivirals used for HSV and VSV?

A

aciclovir oral, IV, eye ointment, cream

valaciclovir oral

famciclovir oral

foscarnet IV

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13
Q

How does aciclovir work?

A
  • Aciclovir is converted by viral thymidine kinase to ACVMP,
  • ACVMP then converted by host cell kinases to ACV-TP (triphosphate)
  • ACV-TP, in turn, competitively inhibits and inactivates HSV-specific DNA polymerase
  • preventing further viral DNA synthesis
  • without affecting the normal cellular processes
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14
Q

When is CMV treated with antivirals?

A

Only life threatening - or sight threatening CMV infections

e.g HIV patients (CMV retinitis, colitis), transplant recipients(pneumonitis)

May also be used to treat neonates with symptomatic congenital CMV infection

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15
Q

What are potential drugs for CMV?

A

Gangciclovir IV, ocular implant

Valganciclovir (oral)

Cidofovir (IV)

Foscarnet (IV)

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16
Q

What is the effect of combined anti-retroviral therapy?

A

Restores immune function in AIDS

Decreaes opportunistic inections

17
Q

What are antivirals for chronic hepatitis B?

A

No drug is consistently able to eradicate hepatitis B infection completely.

The goals of the treatment are HBeAg seroconversion, reduction in HBV DNA and normalisation of LFTs.

Indications for treatment include - High viral load in the presence of active hepatitis (as demonastrated by elevated serum transaminases) and/or evidence of inflammation and fibrosis on histology)

Pegylated interferon alpha (subcut.) - most effective in patients with a viral load and serum transaminases greater than twice the upper limit. Interferon is contraindicated in the presence of cirrhosis.

Nucleoside/tide analogues - these inhibit reverse transcription of pre-genomic viral RNA. Major concern is the selection of antiviral-resistant mutations with lon-term treatment. (This is particularly important with older agents such as lamivudine, which may also promote resistance to newer agents as a result of previous antiviral exposure. Tenofovir and entecavir are potent anti-virals with a high barrier to genetic resistance - most appropriate first-line treatment.

Tenofovir

Entecavir

Adefovir

Lamivudine

Emtricitabine

Telbivudine

18
Q

How long are antivirals for chronic Hep C given?

A

Often 12 to 48 weeks

19
Q

What are the current therapies for chronic hepatitis C?

A

Main aim of the treatment is to eradicate infection.

Cure of the virus is defined as loss of the virus from serum 6months after completing therapy .

Pegylated interferon alpha (subcut) and ribavarin (oral).

Main side effects of pegylated interferon are flu-like symptoms, irritability and depression.

Main side effects of ribavarin are haemolytic anaemia and teratogenicity.

PLUS protease inhibitors (tripple therapy) such as telaprevir and boceprevir.

TRIPLE THERAPY : Pegylated interferon alpha and ribavarin and protease inhibitor (telaprevir)

New directly acting antivirals, incombination (daclatasvir, sofosbuvir)

20
Q

How are oseltamivir and zanamivir used?

A

Used in both treatment and prophylaxis of influenza A and B

Not always indicated but if used, should start within 48 hours of onset of symptoms/contact

21
Q

What is the treatment for respiratory syncytial virus?

A

Ribavarin - rarely indicated

22
Q

How do you test for resistance amongst antivirals?

A

Phenotypic - can virus grow in the presence of compound (HSV)

Genotypic - sequence genome and identify resistance-associated mutations (HIV)

23
Q

When would you suspect a resistant form of HSV?

A

In immunocompromised if there is no response to appropriate antiviral doses within 7 days

24
Q

What is the second line treatment for HSV and CMV if they are resistance to aciclovir?

A

Foscarnet - usually effective

25
Q

When is HIV resistance testing performed?

A

At baseline diagnosis, failing therapy or new treatment approach for other reasons (side effects)

26
Q

When are trough and peak levels of acivlovir needed to be measured?

A

When there is renal impairment

27
Q
A

Infection (17 decks)

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