Antiparasitic drugs Flashcards
OTC treatment for lice
naturally occurring pyrethins
Synthetic pyrethroids
Prescription options for lice
Spinosad 0.9% topical suspension
Benzyl alcohol lotion 5%
Ivermectin lotion 0.5%
Malathion lotion 0.5%
Spinosad MOA
Natural product produced by the bacterium Saccharopholyspora spinose
Activation of nicotinic acetylcholine receptors leading to rapid nervous system death
Pyrethrins MOA
Esters of chrysanthemic acid (II is more effective)
Activation of voltage-gated sodium channels
Entorobiasis (pinworm infection)
Most common helminthic infection worldwide
Fecal-oral transmission
Diagnosis: tape test
Treatment for helminths
Benzimidazoles
Bezimidazoles MOA
Binds to tubulin
Inhibits formation of microtubules
Benzimidazoles cap microtubules
Microtubules continue to be shortened from minus end
Inhibits cell division, secretion of parasite molecules, glucose uptake
Albendazole
Drug of choice for pinworms
Variable absorptions
Rapidly converted to albendazole sulfoxide–>active metabolite
Also used for cysticercosis, hookworms, ascariasis, trichuriasis, and strongyloidiasis
Pyrantel pamoate
Broad-spectrum antihelminth
OTC
Highly effective
Highly insoluble: improves utility for intestinal infections)
Pyrantel pamoate MOA
Depolarizing neuromuscular blocking agent
Causes release of acetylcholine and inhibition of cholinesterase
5 human malaria parasites
Plasmodium flaciparum:
- responsible for most malaria deaths
Plasmodium vivax:
- relapsing malaria–>hypnozoites in liver
Plasmodium ovale
- relapsing
Plasmodium malariae
Plasmodium knowlesi
Tissue schizonticides
kill liver stage parasites
Blood schizonticides
kill erythrocytic forms
Gametecytocides
kill sexual stages
block transmission
Artemisinin
Structure: sesquiterpene lactone endoperoxide
Endoperoxide is the active group
Not active against liver stage or hypnozoites
Commonly paired with longer t1/2 drugs
Astemisinin MOA
Must be activated via heme-iron in food vacuole
May form free radicals and/or inhibit PI3K
Insoluble: only used orally
Artemisinin resistance
mutations in Kelch 13 gene
delays progress through the life cycle
4-substituted quinolines
Interfere with heme polymerization
Resistance associated with lack of accumulation in food vacuole
Chloroquine
Well absorbed orally
Large Vd
Hydroxychloroquine is more commonly stocked in U.S pharmacies
Chloroquine resistance
Mutations in PfCRT1
- localized to food vacuole
- causes reduced accumulation of chloroquine
Overexpression of PfCRT1
Primaquine
8-aminoquinoline
DOC for liver stages (actively growing and hypnozoites*) of P. vivax and P. ovale (in combination with chloroquine)
Metabolized by CYP2D6
Primaquine MOA
Hydroxylation by CYP2D6
Produces H2O2
Primaquine pearls
High risk of hemodialysis in G6PD deficiency
Should not be used in pregnancy
Contraindication: granulocytopenia
Doxycycline
Target components of apicoplast: plant-like organelle
Paired with quinine or quinidine for treatment of falciparum malaria
Used for chemoprophylaxis in areas with high resistance to mefloquine
