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MS2 - Infectious Disease > Antiparasitics > Flashcards

Antiparasitics Flashcards

1
Q

What class of drug is metronidazole?

A

Nitroimidazole

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2
Q

Why is metronidazole toxic to bacteria and parasites but not humans?

A

Pyruvate:ferrodoxin oxidoreductase reduces metronidazole in both prokaryotes. This metabolite is toxic and breaks DNA. In humans, however, the aerobic environment re-oxidizes metronidazole and thus eliminate its toxicity.

Note: this lecturer has metronidazole’s MOA as “enzyme unique to parasite.”

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3
Q

What are two drugs that are related to metronidazole?

A

Nitazoxanide and tinidazole

Tinidazole actually has fewer side effects and is better tolerated.

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4
Q

Metronidazole is contraindicated in what patients?

A
  • First trimester pregnancy
  • Renal insufficiency
  • Hepatic insufficiency
  • Alcoholics (because of disulfiram-like reaction)
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5
Q

Metronidazole is an ____________ of CYP450.

A

inducer

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6
Q

_____________ is commonly used to treat Cryptosporidiosis because it is poorly absorbed and can kill the parasites on the walls of the intestine.

A

Paromomycin

Also, visceral and cutaneous Leishmaniasis

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7
Q

There are two combinations that can treat Toxoplasmosis: ________________.

A
  • pyrimethamine/sulfadiazine

* pyrimethamine/clindamycin

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8
Q

________________ selectively targets parasitic dihydrofolate reductase.

A

Pyrimethamine

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9
Q

Sulfonamides selectively target parasitic _____________.

A

dihydropteroate synthase (substrates PABA and pteridine)

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10
Q

Pentamidine also treats ______________.

A

Leishmaniasis and Trypanosomiasis

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11
Q

How does pentamidine work?

A

It isn’t fully agreed upon, but it might disrupt DNA.

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12
Q

Why is pentamidine given in inhaled form?

A

It is not absorbed orally.

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13
Q

List the three benzimidazoles.

A
  • Thiabendazole (not used because of toxicity)
  • Albendazole
  • Mebendazole
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14
Q

How do the benzimidazoles work?

A

They inhibit microtubule formation, just like vincristine (think of Vin Diesel as the strong man bending the bar at the carnival).

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15
Q

Describe the important differences between mebendazole and albendazole.

A
  • Mebendazole: not absorbed so concentrates in the gut; gets metabolized to inactive products; excreted in bile
  • Albendazole: orally absorbed; distributes to tissues; requires hepatic metabolism for activation; excreted in urine

Because of the above properties, albendazole would be given for neurocysticercosis or hydatid cysts, while mebendazole would be given for intestinal nematodes.

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16
Q

How does pyrantel pamote work?

A

It is an acetylcholine receptor agonist. If it were given intravenously, it would cause paralysis. Fortunately, it is not well absorbed and can be given orally for Enterobiasis.

Ultimately, it concentrates in parasites and causes spastic paralysis.

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17
Q

List two contraindications for pyrantel pamote.

A
  • Liver failure

* Someone taking piperazine

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18
Q

______________ is used for all cestode and trematode (fluke) infections exept hydatid cysts and neurocysticercosis.

A

Praziquantel

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19
Q

Although the mechanism of praziquantel is not known, it’s thought that ______________ may play a role.

A

damaging the integument of the parasite to induce an immune response

20
Q

What two drugs can treat CNS Trypanosomiasis?

A

Melarsoprol and eflornithine

Remember that suramin is for the serum (i.e., the hematologic phase).

21
Q

What drug treats Leishmaniasis?

A

Stibogluconate (like the T-bone steak)

22
Q

When liver cells that have been infected with sporozoites rupture, they release ______________.

A

merozoites

23
Q

The ____________ stage of Plasmodium is infectious to RBCs.

A

merozoite

24
Q

What is a schizont?

A

A replication cycle

25
Q

Which two forms of malaria can lie dormant?

A

P. vivax and P. ovale

26
Q

How do the quinine antimalarials work?

A

Plasmodia metabolize nutrients in an acidic vacuole. When they break down hemoglobin, the heme portion produces oxidative species. The quinine drugs bind to heme and prevent it from polymerizing to its safe form, thus causing the accumulation of ROS.

27
Q

During the febrile stage of malaria, high levels of quinine can be given because ________________.

A

high levels of alpha-1-acid glycoprotein are produced, which binds quinine

Note: because patients often get better with quinine, they down-regulate alpha-1-acid glycoprotein and can have cinchonism.

28
Q

The army did not follow up on those given mefloquine (when it was developed at the Walter Reed Medical Center) and they missed that _______________.

A

mefloquine can cause psychotic disturbances

29
Q

Malarone (atovaquone and proguanil) is very safe. But it can _____________.

A

interact with rifampin, cause rash, and induce nausea

30
Q

_______________ also bind to heme and generate ROS.

A

Artemisinins

31
Q

_____________ is the only drug effective against latent P. vivax or P. ovale.

A

Primaquine (like the primal queen not hypnotized)

32
Q

True or false: metronidazole doesn’t get absorbed and is thus strictly a luminal agent.

A

False. It gets rapidly absorbed and distributes to all tissues, even the CSF.

33
Q

How common is Toxoplasmosis?

A

50% of U.S. adults and 90% of French adults are seropositive by age 50

34
Q

How does suramin work?

A

The mechanism is not fully known, but it’s thought that it may inhibit the parasite glucose metabolic pathway.

35
Q

_____________ has a 1:2,000 incidence of life-threatening adverse effects.

A

Suramin

36
Q

What antiparasitic was brought back on the market due to hair removal side effects?

A

Eflornithine (“It makes your skin as smooth as thE FLOoR.”)

37
Q

What drug treats Strongyloides infection?

A

Ivermectin

38
Q

What are two side effects among the benzimidazoles?

A
  • Albendazole: cholestasis

* Mebendazole and albendazole: teratogens

39
Q

Describe the pharmacokinetics of praziquantel.

A
  • Rapidly absorbed

* 99% eliminated by the liver at the first go

40
Q

A major contraindication to praziquantel is _______________.

A

ocular cysticercosis; the lysing of cestodes in the eye can lead to permanent ocular damage

41
Q

The _____________ stage of P. falciparum and P. malariae is over in four weeks.

A

liver

42
Q

P. falciparum is responsible for roughly ______% of malaria deaths.

A

85

43
Q

When was quinine first used?

A

1633

44
Q

High doses of quinidine can cause ______________.

A

hemolysis, tinnitus, and death

45
Q

Atovaquone works by __________________.

A

disrupting pyrimidine synthesis

46
Q

Proguanil gets metabolized to cycloguanil which is ____________.

A

DHFR inhibitor

MS2 - Infectious Disease (57 decks)

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