Antimicrobial Chemotherapy 2 Flashcards

1
Q

What can fungi be divided into

A
Yeasts
Filamentous fungi (moulds)
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2
Q

What can be used to treat fungi

A

Anti-fungal drugs

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3
Q

What are the categories of anti-fungal drugs

A

Polyenes
Azoles
Allylamines
Echinocandins

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4
Q

What is the mechanism of action for polyenes

A

They bind to ergosterol that is present in the fungal cell wall but not in the bacterial cell wall
This results in an increase in the permeability of the cell wall

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5
Q

What are polyene drugs active against

A

Yeasts

Filamentous fungi

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6
Q

What is a disadvantage of polyene drugs

A

They bind to other sterols (e.g. cholesterol) in mammalian cell membranes and this is the reason for their toxicity

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7
Q

Which polyene can be used intravenously and what is it used for

A

Amphotericin B

Used for serious systemic fungal infection

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8
Q

Describe amphotericin B

A

It is exteremely toxic and has a wide range of side effects (e.g. renal, hepatic and cardiac toxicity)
The lipid complexed formulations of this drug offer a reduced incidence of such side effects

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9
Q

What is nystatin

A

A polyene drug available for topical use only

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10
Q

What do azoles do

A

Inhibit ergosterol synthesis

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11
Q

Name some azoles

A
Old:
Miconazole
Ketoconazole
Newer:
Fluconazole
Voriconazole
Itraconazole
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12
Q

Describe fluconazole

A

Used for oral and parenteral treatment of yeast infections
Has no serious toxicity problems
Resistance among some Candida species is emerging
Resistance can emerge during treatment

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13
Q

Describe itraconazole

A

Active against both yeasts and filamentous fungi, including Aspergillus spp. and dermatophytes.

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14
Q

What does voriconazole treat

A

Aspergillosis

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15
Q

Describe the mechanism of action for allylamines

A

They suppress ergosterol synthesis but act at a different stage of the synthetic pathway from azoles

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16
Q

Name an allylamine

A

Terbinafine (only one in common use)

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17
Q

What are allylamines active against

A

Dermatophyte infections of the skin
(e.g. ringworm, athlete’s foot) and nails (onychomycosis)

Mild infections will be treated topically and more serious infections
(including onychomycosis) orally

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18
Q

Describe the mechanism of action for echinocandins

A

They inhibit the synthesis of glucan polysaccharide in several types of fungi

They are fungicidal against the Candida species and inhibit the growth of several Aspergillus species

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19
Q

Name some echinocandins

A

Micafungin
Caspofungin
Anidulafungin

20
Q

What does virustatic agents

A

Those that inhibit growth and/or replication

21
Q

What are virucidal agents

A

Those that will kill the virus

22
Q

Are anti-viral drugs virucidal or virustatic

A

Virustatic

23
Q

How do anti-viral drugs tend to work

A

Many are nucleoside analogues which

interfere with nucleic acid synthesis

24
Q

How can the treatment of herpes be effective

A

If started early

Will not erdicate any of the viruses

25
Q

What do anti-herpes virus drugs treat

A

Herpes simplex virus
Cytomegalovirus
Varicella-zoster virus
Epstein-Barr virus

26
Q

What is aciclovir

A

An anti-herpes virus drug

A nucleoside analogue

27
Q

What is aciclovir active against

A

Herpes Simplex

Varicella Zoster

28
Q

What must occur for aciclovir to become active

A

Be converted into its active form by an enzyme (thymidine kinase) coded for by the virus genome

29
Q

What is an advantage of aciclovir

A

It’s specific for virus-infected cells and

has very low toxicity for uninfected host cells

30
Q

When is the IV and oral forms of aciclovir used

A

IV: treats severe infections (e.g. herpes encephalitis and VZV pneumonitis)
Oral: cold sores (caused by HSV reactivation)

31
Q

Name some anti-herpes virus drugs (at least 3)

A
Valaciclovir
Famciclovir
Valganciclovir
Foscarnet
Ganciclovir
Cidofovir
32
Q

Describe valaciclovir

and famciclovir

A

Oral agents related to aciclovir

They can treat HSV and shingles

33
Q

What is foscarnet used for

A

HSV, VZV and CMV infections
Highly nephrotoxic
Only given through IV

34
Q

Describe ganciclovir

A

Active against CMV
Toxic and given by IV infusion
Use is largely restricted to treating life or sight threatening infections in the immunocompromised
(e.g. AIDS, transplant recipients)

35
Q

What is valganciclovir

A

Pro-drug of ganciclovir
Oral alternative for some CMV situations
Bone marrow toxicity so close blood count monitoring required

36
Q

When is cidofovir used

A

For CMV retinitis

when other anti-viral drugs are inappropriate

37
Q

What is zidovudine

A

First Treatment for HIV (1987)
A nucleoside analogue which interferes with the action of reverse transcriptase.
It is virustatic

38
Q

What can zidovudine cause

A

Anaemia and neutropaenia

39
Q

How is a HIV patients response to treatment monitored

A

Their viral load and CD4+ cell count

40
Q

How is chronic hepatitis B and C treated

A

With pegylated interferon-a

Hep C also uses oral ribavirin

41
Q

What has limited the use of pegylated interferon-a

A

Its low response rate, serious side effects and

the high cost of treatment

42
Q

What can be used for the treatment of influenza A and B

A

Zanamivir and Oseltamivir

43
Q

What can be used for the treatment of severe respiratory syncytial virus

A

Ribavirin is occasionally used

It must be inhaled as a fine spray to reach the site of infection in the lungs as administration is difficult

44
Q

What is genotypic analysis

A

Helps in choosing rational treatment in selected patients
(e.g. in HIV infection, where the viral load is rising
despite adherence to treatment, or for HSV, VZV or CMV
not responding clinically to apparently adequate dosage).

45
Q

When is drug monitoring used

A

To ensure therapeutic,
but not toxic, serum levels are achieved
For aciclovir, this is usually restricted to patients
with significant renal impairment