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pharmaco > antifungal and antiprotozoal > Flashcards

antifungal and antiprotozoal Flashcards

1
Q

what can anti fungal drugs be split into? what kind of drugs are there

A
  1. For subcutaneous and systemic mycotic infections
    a. Amphotericin B
    b. Antimetabolites antifungals like flucytosine
    c. Echinocandins
    i. Caspofungin
    d. Azole antifungals
    i. triazoles
    1. For cutaneous mycotic infections
      a. Nystatin
      b. Squalene epoxidase inhibitors
      i. Terbinafine
      c. Azole antifungals
      Imidazoles
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2
Q

What is amphotericin B

A

○ A naturally occurring polyene antifungal
Produced by streptomyces nodosus

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3
Q

what does amphotericin do

A

○ Binds to ergosterol in plasma membranes of sensitive fungal cells to form pores
○ Pores disrupts membrane function
§ Allows electrolytes and small molecules to leak from the cell and resulting in cell death

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4
Q

what is amphotericin active against

A

candida albicans

cryptococcus neoformans

many strains of aspergillus

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5
Q

How as amphotericin B administered

A

topical or slow IV

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6
Q

why must amphotericin B coformulated with sodium deoxycholate

A

because they are insoluble in water, can coformulate to form liposomes

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7
Q

How is the CSF penetration of amphotericin B

A

poor CSF penetration, increases with inflammation

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8
Q

how is amphotericin B excreted

A

low level of drugs and metabolite appear in urine over a long period of time, some eliminated in bile.

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9
Q

What are the adverse reactions of amphotericin B

A

fever and chills

nephrotoxicity (most important)
- can cause renal vasoconstriction, can reduce glomerular filtration rate by more than half. Need hydrate patients adequately

hypotension, shock like fall in blood pressure

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10
Q

What is 5- flucytosine

A

○ Is a water soluble fluorinated pyrimidine analogue

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11
Q

What does 5-FC do

A

interferes with fungi DNA synthesis and protein synthesis

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12
Q

is 5-FC fungistatic or fungicidal

A

fungistatic

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13
Q

What is 5-FC usually paired with

A

amphotericin B, which allows 5-Fc to penetrate the cell

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14
Q

what is the pk of 5-FC

A

○ Well absorbed orally
○ Penetrates into CSF
○ 80% of given dose excreted unchanged in urine
Dose must be adjusted in patients with compromised renal function

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15
Q

What are the adverse effects of 5-FC

A

GI effects

Bone marrow suppression which is the most serious

hepatotoxicity

Cat C in pregnancy

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16
Q

What is the mechanism for echinocandins

A

○ Inhibits the activity of glucan synthase complex, resulting in loss of structural integrity of cell wall

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17
Q

what is the distribution of echinocandin

A

○ Undergo extensive protein binding unable to penetrate into CSF

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18
Q

what antifungal activity does caspofungin have

A

§ Good first line option for patients with invasive candidiasis including candidemia

§ Second line option for invasive aspergillosis in patients with who cannot take or failed amphotericin B

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19
Q

what are some adverse effets

A

GIT related symptoms like fever, chills, rashes, skin flushing, thrombocytopenia

20
Q

What is the mechanism of triazole

A

○ Inhibit C-14 a-demethylase ( a CYP450 enzyme). Blocks the demethylation of lanosterol to ergosterol
○ Inhibition of ergosterol biosynthesis disrupts membrane structure and function
§ Inhibits fungal cell growth

21
Q

What are the adverse effects of itraconazole and voriconazole

A

itraconazole associated with cardiotoxicity

voriconazole associated with neurotoxicity

22
Q

What kind of resistance could happen to triazoles

A

○ Mutations in the C-14 a-demethylase gene that lead to decreased azole binding
○ Some strains of fungi have developed efflux pumps that pump the azole out of the cell

23
Q

What are some adverse effects of triazoles

A

nausea, vomiting, headache, skin rashes, hepatotoxicity, Interferes with CYP450 enzymes resulting in drug drug interactions

24
Q

What are the contraindications for triazoles

A

azoles are considered teratogenic, should be avoided in pregnancy unless benefits outweigh risk

25
Q

What is the pregnancy cat for fluconazole itraconazole and voriconazole

A

cat C for the first 2, cat D for the last

26
Q

What is imidazole indicated for

A

○ Have a wide range of activity including candida
-Topical imidazoles have a variety of uses
-Tinea corporis( affect arms, legs and trunk)
- Tinea cruris ( jock itch, affect groin area
-Tinea pedis
- Vulvovaginal and oropharyngeal candidiasis

27
Q

What are some adverse effect of miconazole

A

§ Contact dermatitis, vulvular irritation, edema
§ Gi disturbance when taken orally
Oral use of clotrimazole is associated with elevated liver enzymes

28
Q

What is nyastatin

A

a polyene antifungal with its structure, mechanism of action, resistance profile similar to amphotericin B

29
Q

What is nyastatin used to treat

A

○ Treat oropharyngeal candidiasis, intravaginally for vulvovaginal candidiasis, or topically for cutaneous candidiasis

30
Q

what is the mechanism of action for terbinafine

A

○ Inhibits squalene epoxidase, block the biosynthesis of ergosterol

31
Q

what is terbinafine active against

A

trichophyton, a genus of fungy that causes tinea infections

32
Q

What is terbinafine used for

A

○ Oral terbinafine treat dermatophyte onychomycoses ( fungal infection of nails) and tinea capitis( scalp infection)
§ Because need to accumulate in keratin for it to be effective
○ Topical terbinafine
§ Used to treat tinea pedis, tinea corporis, and tinea cruris

33
Q

What is the pharmacokinetics of terbinafine

A

○ Bioavailability 40% only due to first pass metabolism
§ Highly protein bound and deposited in skin, nails and adipose tissues
○ Oral terbinafine extensively metabolised by several cyp450 isoenzymes
Mainly excreted via urine

34
Q

who should avoid using terbinafine

A

patients with moderate to severe renal impairment or hepatic dysfunction

35
Q

What are some adverse effects of terbinafine

A

Gi disturbance, headache, rash

36
Q

what are some contraindications of terbinafine

A

should not be given to nursing mothers as it accumulates in breast milk

is an inhibitor of yp450 isoenzyme, concomitant use with substrates of that isoenzyme may result in an increase of adverse effects against those agents

37
Q

What are the types of antiprotozoal agent

A

metronidazole

38
Q

What activity does metronidazole have

A

have activity against luminal and systemic infections

39
Q

What is the mechanism of action of metronidazole

A

§ Nitro group of metronidazole serve as electron acceptor, forming reduced cytotoxic free radicals that result in protein and DNA damage
□ Results in the death of the E. histolytica trophozoites

40
Q

What is metronidazole indicated against

A

anaerobes

		§ Used in localised and aggressive periodontitis in combination with amoxicillin or ciprofloxacin, and in anaerobic infections
		§ May be used in conditions involving obligate anaerobes such as fusobacterium prevotella, porphyromonas species such as dentoalveolar abscess and pericoronitis
		§ Amebic infections caused by protozoa like e. histolytica, trichomonas vaginalis, giardia lambila
		§ Anaerobes like bacteroides specifies and CDAD
  • H pylori
41
Q

how is metronidazole absorbed

A

completely and rapidly absorbed after oral administration

42
Q

how is metronidazole distributed

A

§ Distributes well throughout body and tissues and fluids
□ Therapeutic levels can be found in vaginal and seminal fluids, saliva, breast milk, CSF

43
Q

How is metronidazole metabolised

A

Hepatic oxidation of metronidazole side chain by mixed function oxidase, followed by glucuronidation to form at least 2 major active metabolites, which are reduced to inactive metabolites by gut flora

44
Q

what can affect the rate of metabolism of metronidazole

A

concomittant treatment with inhibitors of CYP450

45
Q

What are the adverse effects of metronidazole

A

GI, nausea, vomiting, epigastric disease
unpleasant metallic taste

optical and peripheral neuropathy
oral moniliasis
may potentiate effect of warfarin, avoid taking with alcohol

pharmaco (19 decks)

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