antihelminthic drugs Flashcards
taenia saginata
beef tapeworm, global, undercooked meat, cysticercosis
taenia solium
pork tapeworm, global, uncooked pork, cysticercosis
diphyllobothrium latum
largest tapeworm, undercooked fish, robs host of B12, northern hemisphere
schistosomiasis
schisosoma hematobium, mansoni, japonicum
symptoms due to immune reaction to egg - headaches, fatigue, fever, gastrointestinal problems, hepatic fibrosis, ascites, bladder cancer
praziquantel use against
against flatworms (cestodes and trematodes), no action against nematodes
praziquantel mechanism of action
disrupts clacium homeostasis, muscular contraction and spastic paralysis, worms dislodge and die
praziquantel dosing
two or three doses for schistosomiasis
single doses for T. saginata, solium and D. latum (doesn’t kill eggs of T. solium)
praziquantel toxicity
reaction to dying worms, avoid if pregnant, dizziness and drowsiness (avoid driving)
american hookworm
necator americanus, nematode
old world hookworms
ancylostoma doudenale, nematode
hookworm infection
found in soil
infect by penetrating through skin or oral ingestion
feed on intestinal tissue and blood
live up to 15 yrs
pulmonary lesions, skin reactions, intestinal ulcerations, anemia
pinworms - nematode
enterobiasis, widespread in temperate (US)
live in GI, migrate to rectum to lay eggs, causes perianal pruritis, eggs infect fingers/sheets, ingestion of eggs cause new infection cycle
roundworms - nematode
ascariasis developing countries reside in small intestine penetrate intestinal wall, transported to lungs, trachea and reswallowed poor sanitation
whipworm
trichuriasis
subtropics, SE USA
ingesting eggs in contaminated food/liquids
eggs passed in feces, reside in large intestine, 5 cm length
live 5 years in host
irritation, inflammation of colonic mucosa, abdominal pain diarrhea, distension
trichinella spiralis (nematode) causes
trichinosis - diarrhea, abdominal pain, nausea, muscle pain, edema, weakness infection can be intestinal and systemic undercooked pork (feeding on untreated garbage) first round of replication in intestines progeny distributed throughout body
filariasis
lymphatic dwelling filaria, elephantiasis, transmitted by mosquitoes
organisms causing filariasis
nematodes: wuchereria bancrofti (tropical), brugia malayi (asia), brugia timori (indonesia)
eyeworm
loa loa, transmitted by deer flies, often asymptomatic, ocular lesions can cause blindness, africa
river blindness
onchocerca volvulus, transmitted by female blackflies, africa, blindness, dangerous and infects millions in africa/some areas uninhabitable
types of benzimidazoles
mebendazole, thiabendazole, albendazole
benzimidazoles mechanism
binds to tubulin, inhibits formation of microtubules
benzimidazoles pharmacokinetics
poorly absorbed in GI, fatty meal increases absorption
luminal parasites - empty stomach
tissue infections - with fatty meal
albendazole
converted to sulfoxide form - active metabolite
well tolerated in short term treatments
drug of choice for cysticercosis
also used for pinworms, hookworms, ascariasis, trichuriasis, strongyloidiasis
mebendazole
metabolites not active well tolerated in short term treatments teratogenic pinworms, hookworms, ascariasis, trichuriasis (whipworm) strongyloidiasis
thiabendazole
no longer prefered - toxicity (dizziness, anorexia, nausea, vomiting, should not be used in pregnant women)
metabolites not active
diethylcarbamazine
filariasis and loiasis
microfilariae rapidly killed
well absorbed from GI
well tolerated but reactions to dying worms can be severe
systemic inflammation from release of bacterial endosymbiont
ivermectin
strongyloidiasis, primarily onchocerciasis (single dose)
mass treatment programs - once a year, treat for lifespan of adult worm
semisynthetic macrocyclinc lactone
good oral availability
ivermectin mechanism of action
paralyzes microfilariae, allows host cytotoxic cells to adhere
doesnt kill adult worms, blocks release of progeny
intensifies gaba-mediated transmission of signals to peripheral nerves in worm
affects similar channels in mammalian brain but requires 100-fold higher concentration
pyrantel pamoate
OTC
broad spectrum antihelminth
highly effective for pinworms and ascaris
moderately effective for hookworms
against adult and immature worms (not against migratory stages or ova)
pyrantel pamoate mechanism of action
neuromuscular blocking agent, release of acetylcholine and inhibits cholinesterase - worms paralyzed and expelled
pyrantel pamoate - ascariasis
one dose 11mg/kg, 85-100% effective
pyrantel pamoate - pinworms
two doses, two weeks apart, 95% cure rate
scabies
itch from female burrowing feces
treat with 5% permethrin cream, may need to soften skin/bites with salicylic acid first
lice treatment
1% permethrin or pyrethrin, 2nd application 10 days later
spinosad - newer
trichinosis treatment
mebendzole plus corticosteroids
