Antiprotozoal & Antihelmintic Agents Flashcards
Amebiasis
Entamoeba histolytica
Often infects whole household
Can be symptomatic and asymptomatic (but infective)
Treatment of Amebiasis
Luminal stage (infective cysts in intestines but NOT symptomatic) • Treat with luminal amebicide (paromomycin or Iodoquinol)
Systemic stage (trophozoites in liver —> symptoms!) • Treat with tissue amebicide AND luminal amebicide
DOC for Amebiasis
Metronidazole
Giardiasis
Transmission from contaminated water/food
Most common cause of non-bacteria diarrhea in US
“Beaver fever” - zoonotic disease, colonizes in small intestine —> extreme malabsorption
DOC for giardiasis
Metronidazole
Trichomoniasis
Sexually transmitted urogenital parasite
Men asymptomatic
Women —> vaginitis with frothy, yellow discharge
DOC for trichomoniasis
Metronidazole!
Toxoplasmosis
Common in many animals, especially cats
Mild infection in most but fetal infection —> heart problems, hydrocephalus, retinochorioiditis
Pneumocystosis jirovecii/carina
Not a Protozoa but a yeast like fungi
Major cause of death for AIDS patients (PCP)
HIV therapy may include prophalaxis (Bactrim) against this
Tissue amebicides
***Metronidazole
Tinidazole
Emetine and Dehydroemetine
DOC for toxoplasmosis
Pyrimethamine (Daraprim) plus sulfadiazine plus folinic acid
Luminal Amebicides
Iodoquinol
Paromomycin
Tetracycline and Erythromycin
Metronidazole
DOC for Invasive Amebiasis (symptomatic) + luminal amebicide, Giardiasis and trichomoniasis
MOA for Metronidazole
Prodrug, non-enzymatically reduced by reacting with reduced ferredoxin (only found in anaerobes)
Kills amoeba in tissues but not cysts - combine with a luminal amebicide for amebiasis
Metronidazole adverse side effects
Metallic taste
Disulfiram like reaction to alcohol
Tinidazole
Newer drug derived from metronidazole
Same indications as metro
Same use and adverse side effects
Emetine and Dehydroemetine
Alternative to those who don’t respond to metro to tinidazole but super toxic
Cardiotoxic, serious GI effects, teratogenic***
Only used under compassionate investigational new drug protocol
Iodoquinol
Luminal amebicide used against asymptomatic amebiasis (or given together with Metro for symptomatic)
High iodine content —> iodine-induced thyroid enlargement and some serious adverse eye effects (remove immediately if affected)
Paromomycin
Aminoglycoside that can be used for trichomoniasis, giardiasis, or as a luminal amebicide (because not well absorbed but we don’t need it to be)
NOT oto/nephrotoxic like other aminoglycosides because NOT absorbed
Alternative Abx treatment for amebiasis/giardiasis (luminal)
Tetracycline and Erythromycin
Used in conjunction with metronidazole for symptomatic patients
Pyrimethamine (Daraprim) plus Sulfadiazine
DOC for toxoplasmosis
High dose so some problems with bone marrow
Administer with folinic acid (leucovorin) to counteract bone marrow side fx
DOC for pneumocystis pneumonia (PCP)
Trimethoprim plus Sulfamethoxazole (Bactrim)
Also useful against toxoplasmosis but not as good as Daraprim
Can be used as prophylaxis in AIDS patients but often not tolerated
MOA: inhibits folate synthesis
Toxicity: rash
Pentamidine
Effective against PCP (Bactrim better but this can be used when Bactrim contraindicated)
Can be used in nebulizer for prophylaxis but IM is better
Toxicity: HYPOGLYCEMIA
Most antihelmintic interfere with:
Energy metabolism**
Neuromuscular coordination
Microtubular function
Cell permeability
What is the cause of most side effects from antihelminth drugs?
Immune response (allergic) to the dying worms
Albendazole/Mebendazole
DOC for mixed roundworm infections
MOA - inhibit microtubule polymerization by binding to ß-tubulin—> effects worms’ energy metabolism
Little toxicity because not highly absorbed
SOME teratogenicity/embryotoxicity
Pyrantel Pamoate
OTC drug, useful against a variety of nematodes (roundworm, pinworm, and hookworm)
MOA: cholinesterase inhibitor; produces depolarize great neuromuscular blockage in the worm
Few side fx because little is absorbed
Ivermectin
Effective against lots of nematodes
MOA: paralyzes the parasite, intensifies GABA-mediated transmission of signals in the peripheral nerves
Minimal side fx
Praziquantel
DOC for schistosomes
MOA: increasing the worm’s permeability to Ca2+ —> paralysis—>release
Bithionol
Uncoupled oxidative phosphorylation
Only available from the CDC, for use against flukes
