Antiparasitic drugs Flashcards
which enzyme is unique to parasites?
pyruvate:ferredoxin oxidoreductase (PFOR)
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)
what organism causes amebiasis?
entamoeba histolytica
what organism causes giardiasis?
giardia lamblia
what are the features of giardia, entamoeba, and trichomonas?
anaerobic lumen dwelling protozoans
what enzyme is expressed by giardia, entamoeba, and trichomonas?
PFOR
what is the function of PFOR?
converts pyruvate to acetyl CoA
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
what are the main adverse effects of metronidazole (Flagyl)?
disulfiram effect
what is the drug of choice for treating SYMPTOMATIC DZ?
metronidazole (Flagyl)
what is the problem with metronidazole in amebiasis treatment?
does not kill cyst forms
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
no
when should iodoquinol be used?
following metronidazole
which drug is less toxic - iodoquinol or paromomycin?
paromomycin
what are the opportunistic parasitic infections of AIDS patients and the immunocompromised?
cryptosporidium parvum
pneumocystis jirovecii
toxoplasma gondii
what drug is used against c. parvum?
nitazoxanide
what is the MOA of nitazoxanide?
PFOR inhibitor - disrupts energy metabolism
which agents inhibit folate synthesis in parasites, and which organisms do they target?
TMP-SMX - pneumocystis jirovecii
pyramethamine-sulfadiazine - toxoplasma gondii
what drug is used against pneumocystis jirovecii?
TMP-SMX
what drug is used against toxoplasma gondii?
pyrimethamine sulfadiazine