Antiparasitic agents Flashcards by tcarlso 3

What are the three common targets of antiparasitic chemotherapy?

Enzymes or processes found only in the parasite
Enzymes/processes found in both us and parasite, but only indispensable in the parasite
Common biochemical functions but with different pharmacological properties

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What is an example of a process that is found in both us and parasite, but indispensable in the parasite?

Purine salvage pathway

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What are the three major intestinal protozoans that we have treatments for?

Giardia
Amebiasis
Trichomoniasis

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What are the two different forms of entamoeba histolytica? What does this cause?

Trophozoite and cysts

Dysentery, brain lesions

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What are the two different forms of giardiasis? What does this cause?

Trophozoite and cysts

Dysentery

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What are the two forms of trichomoniasis? What does this cause?

Trophozoite

metronidazole

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What is the drug used to treat giardia?

metronidazole

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What is the drug used to treat Amebiasis?

metronidazole

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What is the drugs that is used to treat trichomoniasis?

metronidazole

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What is the MOA of metronidazole?

Generates ROS that damages DNA

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What is the parasitic enzyme parasites have, that converts metronidazole to its active form?

PFOR (pyruvate;ferredoxin oxidoreductase)

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What is the route for metronidazole? Is it well absorbed?

Oral

Well absorbed

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What are the side effects of metronidazole?

HA
Dry mouth
n/v/d

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What should pts avoid taking with metronidazole? Why?

EtOH

Has a disulfiram like effect

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Who should be treated with trich infection?

Sexual parters

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How effective is metronidazole in the treatment of amebiasis?

Good at killing trophozoites, but need to use something else to kill the cysts

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Is resistance a problem with metronidazole?

Not really, but trich has increased levels

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How is resistance to metronidazole effected?

Increased in the activity of other oxidoreductase

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What are the two drugs that are used to f/u treatment for amebiasis with metronidazole?

Iodoquinol
or
paromomycin

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What is the MOA of iodoquinol? What is it used to treat? What is significant about its absorption?

unknown

f/u treatment for amebiasis (entamoeba histolytica) to get rid of GUT cysts/trophozoites

Poor absorption, so stays in GI tract lumen

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What are the adverse effects of iodoquinol?

GI discomfort

Optic atrophy in children

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What is paromomycin used to treat? MOA?

Entamoeba histolytica

Aminoglycoside–Inhibits protein synthesis

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Is paromomycin effective against trophozoites that have infected other tissues besides the gut?

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Which is more toxic, paromomycin or iodoquinol?

Iodoquinol

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What is cryptosporidium parvum? What dz does it cause? In whom is it usually symptomatic?

Water borne parasite that causes profuse watery diarrhea Immunocompromised

What is the treatment for cryptosporidium parvum?

Nitazoxanide

What is the MOA of nitazoxanide?

interferes with ferredoxin oxidoreductase (PFOR) (disrupts energy metabolism in the parasite)

How is nitazoxanide administered? Is there resistance against this?

Orally No resistance

What is nitazoxanide used to treat?

Cryptosporidium parvum

What is the treatment for pneumocystis-jirovecii?

trimethoprim-Sulfamethoxazole

What is the treatment for toxoplasma gondii?

Pyrimethamine-sulfadiazine

What is the MOA of sulfonamides?

PABA analogs that inhibit the production of pteroic acid from PABA by the enzyme dihydropteroate synthase

What is the MOA of diaminopyrimidines?

Inhibitors of the enzyme DHFR

What are adverse reactions with sulfa drugs?

Rash

What is the basis for selective toxicity with diaminopyrimidines?

parasite DHFR is inhibited at considerably lower concentrations

What is the major adverse effects of pyrimethamine-sulfa?

Hematological abnormalities

What is administered with pyrimethamine-sulfadiazine to prevent folate toxicity?

Leucovorin

Does pyrimethamine-sulfadiazine affect the dormant tissue cysts of toxoplasma?

Is there resistance to TMP-SMX in T-Gondii? P.Jirovecii?

Yes

What are the two forms of malaria that can hide out in the liver?

Vivax and ovale

What are the five drugs that are used to treat malaria (not the liver form of vivax and ovale)?

``` Chloroquine quinine mefloquine Malarone Artminisine ```

What is the only antimalarial that can kill off the liver parts of vivax/ovale?

Primaquine

What is the MOA of chloroquine?

Unclear, thought to interfere with parasites ability to detoxify compounds

What are the side effects of chloroquine?

HA n/v Dizziness/confusion Blurred vision

What stages of malaria does chloroquine kill?

All asexual stages of plasmodium

Which of the antimalarials has a large resistance? Where in the world is it still effective?

Chloroquine-- Everywhere but west of the panama canal

What is the MOA of quinue?

Hb degradation, may complex with parasite DNA

Which antimalarial has the poorest therapeutic:toxic ratio of all?

Quinine

What are the side effects of Quinine?

Cinchonism | Hypoglycemia (quine induces release of insulin)

What causes the hypoglycemia with Quinine administration?

Release of parasites in the blood stream

What stages of the malaria life cycle does quine affect?

All aexual species

What is the MOA of mefloquine?

Hb degradation, may complex with parasite DNA

What are the odd, adverse side effects of mefloquine?

Neuropsychiatric

Is mefloquine used for prophylaxis? Is it well tolerated?

Yes, and yes

How does the treatment dose of mefloquine compare to the prophylactic dose?

3-5x greater

What is the spectrum of mefloquine? Resistance?

Effective against all species of plasmodium

What is the only drug that can get rid of the liver forms of vivax and ovale?

Primaquine

What is the MOA of primaquine?

Interfere with mitochondrial ETC

What is the major toxicity with primaquine?

RBC lysis with G6PD deficiency

What disease can have a hemolytic anemia with antimalarials?

G6PD deficiency

What is the spectrum of use for primaquine? Resistance?

vivax and ovale There are some emerging resistance

What two drugs comprise malarone? What type of malaria is this effective against? Is there resistance against this?

Atovaquone + proguanil p. falciparum malaria No resistance yet

What is the MOA of atovaquone? Spectrum? How well is it absorbed? How well is it tolerated?

MOA ? Poorly absorbed Effective against plasmodium well tolerated

What is the MOA of proguanil?

Inhibits dihydrofolate reductase (DHFR)

Why is proguanil rarely used alone?

Development of resistance

What is the MOA of doxycycline in malaria treatment?

Thought to inhibit the growth of plasmodium by disrupting protein synthesis

What are the major side effect of doxycycline?

Photosensitivity dermatitis | staining of teeth

What is the spectrum and resistance of doxycycline? Resistance?

Effective against all species of plasmodium Little evidence of resistance

What is the MOA of artemisinin?

Interacts with Fe, ROS generation ?

What are the side effects of artemisinin?

n/d

What is the spectrum of artemisinin? Resistance?

Effective against all malaria, but falciparum has resistant strains

What are the 5 intestinal nematode infections?

``` Enterobius vermicularis Ascaris lumbricoides Necator americanus Trichuris trichiura Strongyloides stercoralis ```

What are the 2 general MOAs of anthelminthics?

Inhibit mitosis in the parasite Causes muscle paralysis of the parasite

What are the three benzimidazoles?

Albendazole Mebendazole Thiabendazole

Why is it that it's alright that there is little gut absorption of benzimidazoles?

Treating worms in the intestines

Do you want to take benzimidazole on an empty stomach? Why or why not?

Yes, to cause greatest effect against parasite

Why are benzimidazoles contraindicated in prego?

inhibit mitosis

What are the side effect of benzimidazoles?

GI | CNS disturbances

What is the spectrum of albendazole/mebendazole?

Pinworms, hookworms, whipworms, ascariasis

What is the spectrum of thiabendazole? (2)

Strongyloides | Cutaneous larval migrans

What is the treatment of choice for strongyloides?

Thiabendazole

What is the treatment for cutaneous larval migrans?

Thiabendazole

What causes cutaneous larval migrans?

Ancylostoma duodenale

What is the MOA of Ivermectin?

Causes hyperpolarization in muscles cells, resulting in paralysis of parasite, with NO effect on mammal cells

What is ivermectin used to treat?

Intestinal and extraintestinal infections of: - Strongyloides - loa loa - O.volvulus (river blindness) - Wuchereria bancrofti (filariasis)

What is the advantage of using ivermectin in treatment of parasites?

Can penetrate into tissues

What is the treatment for river blindness?

Ivermectin

Is there resistance with ivermectin?

No evidence

What is the cause of river blindness?

O Volvulus

What disease does Wuchereria bancrofti cause?

Filariasis

What disease does B. Malayi cause?

Lymphatic Filariasis

What is the MOA of pyrantel pamoate?

Activates cholinergic nicotinic receptors in the somatic muscles of nematodes and thereby produces a depolarizing neuromuscular blockade

What is the drug of choice for pinworm?

Pyrantel pamoate

What are the side effects of pyrantel pamoate?

Well tolerated, but mild GI disturbances

What is the treatment of choice for tapeworms and fluke?

Praziquantel

What are the diseases that praziquantel used to treat?

tapeworm and flukes

What is the MOA of praziquantel?

Increases the Ca permeability of the worm's tegument, causing its depolarization

Is praziquantel well absorbed? Tolerated? What are the side effects?

Well absorbed and tolerate HA, dizziness

What is the treatment for Cysticercosis?

Praziquantel