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Erica's ID 3 > Antiparasites > Flashcards

Antiparasites Flashcards

1
Q

Major killers from parasitic infections

A
  1. Malaria
  2. Schisto
  3. Trypanosomiasis
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2
Q

Why do most of these drugs get selectively concentrated into the parasite?

A

This is due to GI absorption and location of the parasites

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3
Q

Nitroimidazoles

A
  • pro-drug targets an enzyme that is unique to the parasite
  • causes oxidative damage to the parasite due to free radical.
  • Safe in humans because of aerobic respiration regenerating the parent drug
  • Renal excretion
  • Target : anaerobes
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4
Q

You have a pt that comes in with severe diarrhea and fatty stools after traveling and having ice in their drink. What do you treat them with?

A

Metronidazole because they have giardiasis.

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5
Q

What does metronidazole taste like?

A

Like chewing a battery… so metallic and nasty.

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6
Q

Adverse reactions / contraindications of metronidazole

A
  • HA and Nausea
  • Peripheral neuropathy
  • 1st trimester preg
  • Liver disease
  • Renal dysfunction
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7
Q

Drug interactions of metronidazole

A
  • Alcohol induces disulfiram like state (n/v)
  • Disulfiram
  • Inducers of hepatic enzymes
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8
Q

Paromomycin

A

Aminoglycoside antibiotic
MOA: binds to A-site of ribosomes to inhibit protein synthesis
- Low absorption so concentrated in parasite in gut.

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9
Q

What do you treat with paromomycin

A
  • Amebiasis
  • Leishmanias
  • Cryptosporidiosis
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10
Q

Treatment of toxo

A

Pyrimethamine _ sulfadiazine or if sulfa allergy go for clindamycin

  • antifolate combinations that selectively target parasite enzymes
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11
Q

Where do sulfonamides inhibit?

A

PABA + pteridine —X—> Dihydropteroic acid

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12
Q

Where does pyrimethamine inhibit?

A

@ DHFR

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13
Q

Pentamidine treats..?

A

Used mostly for P. carinii for PCP, alternative to TMP-SMX

West african Trypanosomiasis

Visceral Leishmanias

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14
Q

How does pentamidine work

A

Inhibit SAM decarboxylase to disrupt polyamine biosynthesis

Bind minor groove of DNA to inhibit protein synthesis

Inhibit type II topoisomerase

Interferes with glucose metabolism

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15
Q

Drug interactions of pentamidine

A

Methotrexate - DHFR inhibitor

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16
Q

Which route of administration of pentamidine is used today, and how is it tolerated?

A

Inhalation and it is well tolerated with few side effects

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17
Q

Benzimidazoles treat what…?

A

Nematode infections

Focus on mebendazole and albendazole because thiabendazole has lots of side effects.

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18
Q

MOA of Benzimidazoles

A

Inhibit microtubule formation by binding the beta-tubulin to prevent formation of alpha/beta dimers

Selectively binds to parasite tubulin (100x fold selectivity over human)

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19
Q

What causes the selectivity for benzimidazoles?

A

Humans have a point mutation: Phe200–>Tyr which introduces an -OH group that the drug won’t pick.

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20
Q

Mebendazole

A
  • Poor absorption so good concentration in parasite
  • 95% bound to plasma protein
  • Metabolism to inactive products
  • Bile elimination
  • Use in uncomplicated nematode infections
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21
Q

Albendazole

A
  • Better absorption
  • Systemic distribution
  • Metabolism to sulfoxide required for activity
  • Renal elim
  • Use for cysticercosis
22
Q

Are the benzimidazoles safe in pregnancy?

A

No! Not safe in pregnancy of

23
Q

You have someone with symptomatic epilepsy presenting to your clinic and you suspect cysticercosis. What do you treat with?

A

Albendazole

24
Q

Pyrantel Pamoate

A

Use for roundworm, hookworm, and pinworm infections

  • concentrates in parasite
  • MOA = ACh receptor agonist = spastic paralysis of worm

Contraindications:
- liver dysfunction

DDI:
- Piperazine - Ach receptor antagonist

25
Q

Praziquantel

A

Use for tapeworm and flukes besides cysticercosis

MOA: Ca2+ ionophore - induces tegmental damage and activates the immune system. induces paralysis, detachment and excretion

26
Q

When do you avoid praziquantel?

A
  • if there is a risk of neurocysticercosis because it can cause permanent damage
  • Don’t use in pregnancy
27
Q

What treats leishmania?

A

Sodium stibogluconate

28
Q

Treatment goals of malaria infection

A
  1. Prophylaxis to prevent infection
  2. Treat acute febrile stage of infection
  3. Eradicate latent forms
29
Q

Chloroquine

A
  • Used to treat erythrocytic stage of malaria
  • More potent and less toxic than quinine
  • Anti-cancer drug targeting autophagy
30
Q

MOA of Chlorquine

A
  • Concentrates in food vacuoles
  • Inhibits heme polymerization
  • inhibits peroxidase and catalase activity
  • generates oxidative stress
31
Q

What does failure to respond to chloroquine mean?

A

Resistant infection

32
Q

Adverse reactions to chloroquine

A
  • transiently high dose
  • CV effects
  • CNS dysfunction (coma, confusion, convulsion)

Symptoms of cinchonism

33
Q

Quinine

A
  • treatment of MDR malaria

- Used as a combo drug with lots of Abx

34
Q

MOA of quinine

A
  • Inhibits parasite feeding mechanism
  • Generates oxidative stress

Resistance:
- Increased levels of PfMDR protein Pgh-1

35
Q

Cinchonism

A
  • Visual impairments
  • Auditory tinnitus
  • GI n/v rashes
36
Q

Pharmacokinetics of quinine

A
  • during febrile stages it binds an a-1-acid glycoprotein which lowers bioavailability and decreases the half life.
  • during afebrile stages get higher availability and lower half life.

If not responding to drug early on, try to lower dose so that you don’t have side effects.

If loading dose is IV, switch to oral as soon as possible

37
Q

DDIs of Quinine

A

May raise plasma levels of anticoagulants and cardiac glycosides

38
Q

Adverse reactions of quinine

A
  • Cinchonism
  • Stimulates pancreatic beta-cells
  • Hypotension
  • Hemolysis in G6PD deficiency
39
Q

Mefloquine

A
  • Alternative treatment of erythrocytic stages of chloroquine resistant malaria
  • Prophylaxis during pregnancy
  • Causes a lot of psychotic disturbances
40
Q

MOA of mefloquine

A
  • same as chloroquine (oxidative stress)
41
Q

Adverse reactions of mefloquine

A
  • safe drug if you don’t get the psychoses
42
Q

Malarone

A
  • combo drug (atovaquone + proguanil)

- used for P. falciparum malaria, PCP, and toxo

43
Q

Adverse effects of malarone

A

Rash - history of skin reactions

44
Q

DDIs of malarone

A

Rifampin -used to treat pulmonary infection to reduce plasma levels

45
Q

MOA of malarone

A

DHFR inhibitor

Increases the efficacy of atovaquone to collapse protein gradient

46
Q

Contraindications to malarone

A

Don’t give to kidney disease people.

47
Q

Primaquine

A
  • ONLY drug to treat latent forms of malaria
  • Use in combo with blood schizonticide (chloroquine)
  • Gametocidal activity

Reserve this for latent because it’s the only one we have and you don’t want resistance to develop!

48
Q

Artemisinin

A
  • The drug of choice for MDR malaria in endemic areas

- Use in combo with chloroquine

49
Q

MOA of artemisinin

A
  • interacts with heme and prevents heme polymerization
50
Q

What problems did we have with using artemisinin

A
  • Requires 6 day treatment.. hard to get people to do

- Quick resistance developed in SE Asia

51
Q

MOA of primaquine

A
  • Inhibit electron transport chains.
52
Q

Adverse reactions to primaquine

A
  • GCPD deficiency leads to hemolytic anemia and can be life threatening!! ALWAYS TEST!

Erica's ID 3 (13 decks)

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