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Pharmacology > Antiparasitics: antiprotozal drugs > Flashcards

Antiparasitics: antiprotozal drugs Flashcards

1
Q

Trypanosoma cruzi is also called ….

its transmitted by …

A

chagas disease

-rejuvid bug transmits it - bug defecates on skin and then later person itches the fecal matter into the skin

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2
Q

Taenia solium, aka …

it causes …

A

pork tapeworm

-causes cysticercosis and neurocyticercosis

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3
Q

Toxicara is typically a ____ infection

-its ____ ___ worm

A

zoonotic

  • dog and cat roundworm
  • people get infected by ingesting infected feces (i.e. ingesting infected soil)
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4
Q

Toxoplasma gondii is most problematic for …

A

pregnant women - can cause birth defects

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5
Q

Trichomonas

-transmission

A

sexually transmitted

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6
Q

Parasitic infections associated with HIV in US

A

Pneumocystic jirovecii
Toxoplasma gondii
Cryptosporidium (assoc. w/ contaminated drinking water)

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7
Q

Parasitic infections associated with HIV globally

A

Malaria
Leishmania
Trypanosoma cruzi

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8
Q

What are the 5 types of human malaria?

A 
Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi
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9
Q

P. falciparum

A

responsible for most deaths
prodominant in tropics
infects all RBCs

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10
Q

P. vivax

A

relapsing malaria - caused by hypnozoites in liver - infects reticulocytes

common in subtropics and temerpate regions

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11
Q

P. ovale

A

relapsing malaria - caused by hypnozoites in liver

found in west Africa

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12
Q

Malaria life cycle

A

-sporozoites injected by mosquito - go to liver

  • liver
    • – merozoites formed
    • – hypnozoites — vivax and ovale latent form causes relapse
  • blood
    • – merozoites invade & divide, rupture RBC, reinvade
    • –sexual stages produce gametocytes
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13
Q

What can happen in terms of effects of malaria?

A
  1. cerebral malaria
  2. severe anemia
  3. metabolic acidosis

drugs that we have don’t treat these symptoms

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14
Q

Can we prevent malaria infection?

A

No, we don’t have drugs that kill sporozoites

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15
Q

What does it mean to be a tissue schizonticide? blood schizonticide?

A

tissue - acts on liver forms

blood - acts on RBC forms

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16
Q

What do gametocides do?

A

kill sexual stages & prevent transmission to mosquito

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17
Q

What drug works against both merozoites and hyp?

A

primaquine

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18
Q

What drugs are effective against merozites only?

A

atovaquone

artemisinins

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19
Q

Drugs that are effective against blood stages?

A 
chloroquine
mefloquine
artemisinins
quinine
doxycyline & tetracycline
clindamycin
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20
Q

What factors must be considered when treating someone for malaria?

A
  1. types of infecting parasite
  2. area where infection was required - this determines the resistance pattern
  3. clinical status of the patient
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21
Q

Artemisinin

  • what important feature does it have?
  • mechanism?
A
  • Endoperoxide active group (required for the functioning of this drug)
  • Mech not clear, but may involve toxic free radicals
    • – active compound likely produced through interaction with intracellular iron
22
Q

What is one of the big advantages of artemisinin?

what is the disadvantage?

A

It acts very quickly on the blood schizonticide
— 4 log reduction in parasite numbers in 48 hours

Short half-life

23
Q

Artemisinin is active against … ?

What is it recommended for?

A

Active against all

Recommended for treatment of chloroquine-resistant P. falciparum

24
Q

Artemisinin combination therapy

  • what is it combined with?
  • what is the idea behind this therapy?
  • what is the down side?
A

combined with mefloquine or lumefantrine

idea is to combine it with something that has a long half life

artemisinin is better tolerated that most drugs so we don’t want to adversely affect patient with addition of another drug

25
Q

How does artemisinin kill?

A

concentration dependent killing - meaning the higher the dose, the more effective the killing

26
Q

What are the artemisinin derivates and how are they administered?

A
  1. artemisinin - oral
  2. artesunate - oral, IV, IM, rectal
  3. dihydroartemisinin - oral
  4. artemether - oral, IM, rectal
27
Q

Artemisinin adverse effects

A

nausea, vomitting, diarrhea, dizziness

embryotoxic - not recommended in first trimester for uncomplicated malaria

28
Q

How do 4-substituted quinolines work? Why does this work?

Resistance?

A

Interfere the polymerization of heme

Parasite ingests large amounts of Hg and degrade it. Free heme is toxic, so parasites polymerize it into hemozoin. The drugs prevent this pairing of heme molecules

R: Associated with lack of accumulation in food vacuole

29
Q

Pharmacokinestics of chloroquine (generally)

A
  1. well absorbed
  2. very large Vd - slowly released from tissues
  3. initial half life of 3-5 days; terminal half life of 1-2 months
30
Q

The effect of chloroquine is best seen with what kind of mechanisms of killing?

A

Time-dependent killing

note: this makes sense with the properties

31
Q

What is the primary mechanism by which resistance was developed to chloroquine?

A

Mutations in PfCRT1

  • localized to food vacuole
  • causes reduce accumulation
32
Q

Adverse effects of chloroquine

A

Adverse - Pruritus (esp Africans)

33
Q

CONTRAINDICATIONS of chloroquine

A

Contraindications

  1. psoriasis or prophyria
  2. retina or visual field defects
  3. myopathy
34
Q

Other chloroquine related compounds

A
  1. mefloquine
  2. lumefantine
  3. piperaquine
  4. amodiaquine
  5. halofantrine
  6. tafenoquine
35
Q

Quinine and Quinidine act against?
Active against what others?
First line for what malaria?
Administration?

A

rapidly acting against blood schizonticide

active against Plasmodium and babesiosis

first line for falciparium

administration - oral for uncomplicated, IV for severe

36
Q

What CYP are quinine and quinidine metabolized by?

A

CYP3A4

  • can raise levels of warfarin and digoxin
  • interacts with antiretroviral drugs
37
Q

Adverse effects of quinine

A

Cinchonism

  • tinnitus
  • headache
  • nausea
  • dizziness
  • flushing
  • visual distrubances

Cardiotoxicity

Can stimulate uterine contractions

Hemolysis

  • G6PD deficiency
  • blackwater fever

Severe hypotension can occur from too-rapid infusion

38
Q

MELFLOQUINE [Larium]

Used for what types of malaria?
Adverse effects?

A

erythrocytic forms - falciparum & vivax

used for both prophylaxis and rx

Adverse effects - neuropsychiatric toxicity

39
Q

What things are seen with neuropsychiatric toxicity?

A

seizures
toxic psychosis
sleep disturbances

^recall, this is seen with MELFLOQUINE

40
Q

Primaquine

Used for what stages?

A

Drugs of choice for liver stages of P. vivax and P. ovale

Its the only drug active against hyponozoites

It is gametocidal against all four malaria parasites

41
Q

Primaquine contraindications?

Avoid in?

A

Contraindications

  • G6PD deficiency
    • –predisposes to hemolytic anemia
    • –pregnancy - fetus is G6PD deficieny

Avoid in

  • history of granulocytopenia or methmoglobinemia
  • receiving potentially myelosuppressive drugs
  • disorders that commonly include myelosuppression
42
Q

Sulfadoxine targets …

A

DHPS (dihydropteroate synthase)

43
Q

Pyrimethamine proguanil targets …

A

DHFR (dihydrofolate reductase)

44
Q

Fansidar =

A

prymethamine-sulfadoxine

  • folate synthesis inhibitors
  • slow acting erythroctic schizonticide
45
Q

Use of antifolates

-recommendation. why?

A
  • use of single antifolates not recommended
  • synergistic effect allows 20-fold reduction in dose of each component
  • combo chosen because of matching pharmacokinetics (both have long half-lives)
46
Q

Other uses of antifolates

A
  1. toxoplasmosis
  2. pneumocystis

(Pyrimethamine is 1000-fold selective for plasmodium)

47
Q

Why is use of single antifolates not recommended?

A

resistance develops easily

48
Q

Malarone is a combination of ..?

A

proguanil and atavaquone

49
Q

What is atavaquone’s mechanism of action?

A
  • disrupts mitochondrial electron transport

- failed when used alone due to rapidly developed resistance

50
Q

What antibiotics have been showed to be effective as anti-malarials?

Why are these effective?

A
  1. tetracycline
  2. doxycycline
  3. clindamycin
    (1-3 are blood schizonticides)

Parasite has a plant like organelle called apicoplasts - they carry out biochemical processes. These antibiotics target the organelle

Pharmacology (45 decks)

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