Antiparasitic drugs Flashcards by Michael Gedestad

which enzyme is unique to parasites?

pyruvate:ferredoxin oxidoreductase (PFOR)

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what are the three targets for antiparasitic chemotherapy?

enzymes found only in parasite (PFOR)
enzymes in both host and parasite but indispensable only in the parasite (purine salvage)
common biochem functions in both host and parasite, but different pharmacological properties (DHFR, microtubule disrupters)

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what organism causes amebiasis?

entamoeba histolytica

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what organism causes giardiasis?

giardia lamblia

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what are the features of giardia, entamoeba, and trichomonas?

anaerobic lumen dwelling protozoans

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what enzyme is expressed by giardia, entamoeba, and trichomonas?

PFOR

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what is the function of PFOR?

converts pyruvate to acetyl CoA

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how does metronidazole (Flagyl) kill parasites?

acts as an electron sink within the cell

activated (reduced) by PFOR under anaerobic conditions

reactive intermediates form which bind to and disrupt protein and DNA structure and function

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what are the main adverse effects of metronidazole (Flagyl)?

disulfiram effect

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what is the drug of choice for treating SYMPTOMATIC DZ?

metronidazole (Flagyl)

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what is the problem with metronidazole in amebiasis treatment?

does not kill cyst forms

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what drugs are effective at eliminating trophozoite and cyst forms of e. histolytica from the LUMEN of the intestine? are they effective in the tissues?

iodoquinol and paromomycin

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when should iodoquinol be used?

following metronidazole

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which drug is less toxic - iodoquinol or paromomycin?

paromomycin

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what are the opportunistic parasitic infections of AIDS patients and the immunocompromised?

cryptosporidium parvum
pneumocystis jirovecii
toxoplasma gondii

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what drug is used against c. parvum?

nitazoxanide

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what is the MOA of nitazoxanide?

PFOR inhibitor - disrupts energy metabolism

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which agents inhibit folate synthesis in parasites, and which organisms do they target?

TMP-SMX - pneumocystis jirovecii

pyramethamine-sulfadiazine - toxoplasma gondii

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what drug is used against pneumocystis jirovecii?

TMP-SMX

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what drug is used against toxoplasma gondii?

pyrimethamine sulfadiazine

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what are the inhibitors of folate synthesis?

sulfonamides

diaminopyrimidines

what is the MOA of the sulfonamides?

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

what is the MOA of diaminopyrimidine?

inhibit DHFR - prevents formation of THF

what is the main adverse reaction of the sulfonamides?

rash

what drug is used to treat toxoplasmosis?

pyrimethamine-sulfadiazine

what drug is administered to prevent folate deficiency from pyrimethadine-sulfadiazine treatment?

leucovorin

what drug can kill the dormant forms of p. vivax and p. ovale?

primaquine

is there resistance to chloroquine?

yes

what are the adverse effects of quinine?

cinchonism - tinnitus, temporary hearing loss, headache, nausea, vomiting hypoglycemia - induces insulin release

what is the MOA of quinine?

eliminates asexual erythrocytic stage of all plasmodium species

what is the main adverse reaction for mefloquine?

severe neuropsychiatric reactions

what is the major toxicity associated with primaquine?

hemolysis in G6PD patients

malarone is a combination of which drugs? what is the clinical use?

atovaquone and proguanil p. falciparum treatment, prophylaxis

what must be checked prior to primaquine administration?

G6PD status

what is the MOA of proguanil?

DHFR inhibitor

what is the indication for doxycycline in malaria treatment?

prophylaxis and treatment

what is the major side effect of doxycycline?

photosensitivity dermatitis

which drug works well against multidrug resistant strains of p. falciparum?

artemisinin

what are the general (proposed) MOAs of antihelminthics?

inhibit mitosis in parasite muscle paralysis of parasite

what are the benzimidazole antihelminthics?

albendazole mebendazole thiabendazole

what is the toxicity associated with benzimidazoles?

thiabendazole GI - anorexia, nausea, vomiting CNS - delirium, hallucinations albendazole and mebendazole GI

which antihelminthic drugs are contraindicated during pregnancy?

benzimidazoles

albendazole and mebendazole are useful against which worms?

ascariasis pinworm hookworm whipworm

what is the clinical use for thiabendazole?

second line for strongyloidiasis (intestinal and tissue) topical for cutaneous larval migrans

what is the MOA of ivermectin?

hyperpolarization is muscle cells - paralysis

ivermectin is the drug of choice for which worm(s) / condition(s)?

strongyloidiasis river blindness, eye worm, filarial worms

what is the drug of choice for strongyloidiasis?

ivermectin

what is the drug of choice for pinworm?

pyrantel pamoate

what is the MOA of pyrantel pamoate?

activates cholinergic nicotinic receptors in somatic muscles of nematodes - neuromuscular blockade

what is the drug of choice for tapeworms and flukes?

praziquantel

what is the MOA of praziquantel?

increases calcium permeability of worm's tegument - causes depolarization