52-Antiparasitic Drugs Flashcards
3 targets for antiparasite therapy?
1-Enzymes or processes found only in the parasite (PFOR; folate synthesis)
2-Enzymes or processes found in both parasite and host but indispensable only in the parasite (purine salvage pathways)
3-Common biochemical functions found in both parasite and host, but with different pharmacologic properties (DHFR; microtubule disrupters)–different binding affinity to parasite and host
Metronidazole mechanism
activated by PFOR in anaerobic conditions. Used for trichomoniasis, giardiasis and amebiasis (doesn’t kill cyst forms in amebiasis)
Why follow up Metronidazole treatment with something else? what?
doesn’t kill cyst forms. Use Iodoquinol or paromomycin to eradicate cyst forms
Iodoquinol use and adverse effects
use to eliminate trophozoite and cyst forms of E. histolytica (amebiasis) in lumen (poorly absorbed)
causes optic atrophy and permanent vision loss in kids
also 20 day regimen!
Paromomycin
Similar to Iodoquinol, but less toxic and shorter regimen (7 days)
Nitazoxanide use and MOA
use for cryptosporidiosis (common in AIDS patients)
Interferes with PFOR
Sulfonamides
names and mechanism
sulfamethoxazole and sulfadiazine
PABA analogs that block folate synthesis by inhibiting dihydropteroate synthase. Pyrimethamine-Sulfadiazine treatment can induce folate deficiency so administer folinic acid to avoid deficiency
Diaminopyrimidines
names and mechanism
pyrimethamine and trimethoprim
inhibit the enzyme DHFR and block folate synthesis. Inhibits parasite DHFR at much lower concentrations than the mammalian.
sulfonamides adverse reactions
rash and hemolysis
Treatment choice for toxoplasmosis?
Pyrimethamine-Sulfadiazine
higher doses for active disease and lower dose for lifelong maintenance
Treatment for Pneumocystis jirovecii infection?
Trimethoprim-Sulfamethoxazole
higher doses for active disease and lower dose for lifelong maintenance
Chloroquine
malaria drug with big time resistance. Don’t give this one very often
Quinine
3 adverse
Poorest therapeutic:toxic ratio of all antimalarial drugs causes cinchonism (vestibulocochlear) and hypoglycemia (which can already be a problem in chronic infection)
Mefloquine
malaria drug with neuropsychiatric reactions in .5% of patients being treated for malaria
Primaquine
use, adverse
The only antimalarial with activity against liver (hypnozoite) forms of P. vivax and P. ovale.
Can cause hemolysis in people with G6PD deficiency!
Malarone
malaria drug combination of atovaquone and proguanil.
proguanil inhibits DHFR
Doxycycline
use, adverse
can be used for malaria prophylaxis or treatment.
causes photosensitivity dermatitis and stains teeth in children
Artemisinin Derivatives
extracted from “chinese wormwood”
works against drug resistant strains.
Antihelminthic drugs MOA
can inhibit mitosis (benzimidazoles) or cause muscle paralysis (ivermectin, pyrantel pamoate, and praziquantel)
Benzimidazoles
names and side-effects/contraindications
Albendazole, mebendazole, thiabendazole
All have GI side-effects and thia has CNS disturbances. Contraindicated for pregnancy and kids under 2
What drugs used to treat ascariasis, pinworm, hookworm and whipworm?
albendazole/mebendazole
What to treat strongyloidiasis and cutaneous larval migrans?
Thiabendazole
Ivermectin MOA and use?
causes hyperpolarization in muscle cells.
drug of choice for strongyloidiasis
Pyrantel Pamoate MOA and use?.
activates cholinergic nicotinic receptors in nematodes which paralyzes them.
drug of choice for pinworm
“pyrantel pamoate paralyzed pinworm”
Treatment of choice for tapeworm and fluke infections?
Praziquantel
Praziquantel MOA, use/dose
increases calcium permeability of worm’s tegument
flukes: 3 doses single day
tapeworms: single dose
cysticercosis: two weeks
