Antiparasitic agents Flashcards
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
What is an example of a process that is found in both us and parasite, but indispensable in the parasite?
Purine salvage pathway
What are the three major intestinal protozoans that we have treatments for?
Giardia
Amebiasis
Trichomoniasis
What are the two different forms of entamoeba histolytica? What does this cause?
Trophozoite and cysts
Dysentery, brain lesions
What are the two different forms of giardiasis? What does this cause?
Trophozoite and cysts
Dysentery
What are the two forms of trichomoniasis? What does this cause?
Trophozoite
metronidazole
What is the drug used to treat giardia?
metronidazole
What is the drug used to treat Amebiasis?
metronidazole
What is the drugs that is used to treat trichomoniasis?
metronidazole
What is the MOA of metronidazole?
Generates ROS that damages DNA
What is the parasitic enzyme parasites have, that converts metronidazole to its active form?
PFOR (pyruvate;ferredoxin oxidoreductase)
What is the route for metronidazole? Is it well absorbed?
Oral
Well absorbed
What are the side effects of metronidazole?
HA
Dry mouth
n/v/d
What should pts avoid taking with metronidazole? Why?
EtOH
Has a disulfiram like effect
Who should be treated with trich infection?
Sexual parters
How effective is metronidazole in the treatment of amebiasis?
Good at killing trophozoites, but need to use something else to kill the cysts
Is resistance a problem with metronidazole?
Not really, but trich has increased levels
How is resistance to metronidazole effected?
Increased in the activity of other oxidoreductase
What are the two drugs that are used to f/u treatment for amebiasis with metronidazole?
Iodoquinol
or
paromomycin
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
What are the adverse effects of iodoquinol?
GI discomfort
Optic atrophy in children
What is paromomycin used to treat? MOA?
Entamoeba histolytica
Aminoglycoside–Inhibits protein synthesis
Is paromomycin effective against trophozoites that have infected other tissues besides the gut?
No
Which is more toxic, paromomycin or iodoquinol?
Iodoquinol
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?
No
Is there resistance to TMP-SMX in T-Gondii? P.Jirovecii?
Yes