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Pharm > 2: Antihelminthics > Flashcards

2: Antihelminthics Flashcards

1
Q

how do parasites differ from other parasites?

A
  • multiply outside of their definitive host

- evade immune system: chronic infections last for lifetime of host

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2
Q

what is the most common helminth infection?

A

ascaris

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3
Q

describe echinococcosis:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • from echinococcus granulosus (dog tapeworm)
  • infection: large, hydatid cysts in liver, lung, brain
  • anaphylactic rxn can occur if cyst ruptures
  • follows ingestion of eggs in dog feces
  • intermediate host: sheep
  • ddx: CT scan or biopsy of infected tissue
  • tx: albendazole and surgical excision of intact cysts
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4
Q

describe taeniasis (pork):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • from Taenia solium (pork tapeworm)
  • infection: intestines - diarrhea, but most asymptomatic
  • follows ingestion of larvae in undercooked pork
  • ddx: detection of proglottids in stool
  • tx: niclosamide
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5
Q

describe cysticercosis:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Taenia solium larvae
  • infection: cysticerci in brain - seizures, headache, vomit - and in eyes
  • follows ingestion of eggs from human feces
  • ddx: CT, MRI, or biopsy
  • tx: praziquantel, albendazole, and/or surgery
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6
Q

describe taeniasis (beef):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Taenia saginata (beef tapeworm)
  • infection: intestine but no cysticerci, most asymptomatic
  • follows ingestion of larvae in undercooked or raw beef
  • ddx: detection of proglottids in stool
  • tx: niclosamide
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7
Q

describe diphyllobothriasis:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Diphyllobothrium latum (fish tapeworm)
  • intestinal disease
  • follows ingestion of larvae in undercooked or raw fish
  • ddx: detection of characteristic eggs in stool
  • tx: niclosamide
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8
Q

life cycle of pork/beef tapeworms

A

eggs in environment -> cattle/pigs ingest plants contaminated by eggs or gravid proglottids -> oncospheres hatch, penetrate intestinal wall, and circulate to musculature -> oncospheres develop into cysticerci in muscles -> humans infected by ingesting raw/undercooked meat

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9
Q

how does cysticercosis develop in humans?

A

oncospheres hatch in intestine, invade wall, and migrate to striated muscles, brain, liver, and other tissues -> develop into cysticerci

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10
Q

describe enterobiasis (pinworm disease):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Enterobius vermicularis
  • infection: pruritis ani, white worms visible in stool or perianal region
  • follows infestion of eggs (humans only host)
  • ddx: scotch tape test
  • tx: mebendazole or pyrantel pamoate
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11
Q

what is the most common helminthic infection in US?

A

pinworm

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12
Q

describe ascariasis (roundworm):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Ascaris lumbricoides
  • infection: larvae grow in intestine - abdominal sx, including obstruction; may pass through blood to lungs
  • second most common to pinworms
  • follows ingestion of soil containing eggs
  • ddx: detection of characteristic eggs in stool
  • tx: pyrantel pamoate or mebendazole
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13
Q

describe trichuriasis (whipworm):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Trichuris trichiura
  • infection: usually asymptomatic, but can get abdominal pain, diarrhea, flatulence, rectal prolapse
  • follows ingestion of soil with eggs
  • ddx: identify characteristic eggs in stool
  • tx: mebendazole
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14
Q

describe hookworm disease:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Ancyclostoma duodenale, Necator americanus
  • infection: attaches to intestinal mucosa - anorexia; ulcer-like sx, chronic intestinal blood loss - anemia
  • follows direct skin penetratino by larvae found in soil
  • ddx: identify characteristic eggs in stool
  • tx: pyrantel pamoate or mebendazole
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15
Q

describe strongyloidiasis (threadworm):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Strongyloides stercoralis
  • infection: benign in healthy folks, can be fatal in immunocompromised due to dissemination to CNS or other deep organs (hyperinfection syndrome)
  • follows direct skin penetration by larvae found in soil
  • ddx: identify larvae in stool
  • tx: thiabendazole, albendazole, or ivermectin
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16
Q

describe onchocerciasis (river blindness):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Onchocerca volvulus
  • infection: subcutaneous nodules, prurutic skin rash, ocular lesions -> blindness
  • follows bite of blackfly
  • ddx: detection of microfilariae in skin biopsy
  • tx: ivermectin and/or surgery
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17
Q

describe visceral larva migrans:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Toxocara canis
  • infection: young kids - matures in intestines, then migrates to liver, brain, eyes
  • only larvae cause disease
  • follows ingestion of eggs from dog feces
  • ddx: detect larvae in tissue
  • tx: mebendazole or thiabendazole
18
Q

describe filariasis (elephantiasis):

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Wuchereria bancrofti or Brugia malayi
  • infection: block flow of lymph, causes edematous arms, legs, and scrotum
  • follows bite of infected female Anopheles and Culex mosquitos
  • ddx: microfilariae in blood
  • tx: combo of diethylcarbamazine and albendazole
19
Q

describe trichinosis: -what worm?

  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Trichinella spiralis
  • encysts in tissue
  • follows eating encysted larvae in undercooked pork
  • allergic manifestations treated for sx and not with antihelminthic drugs
  • ddx: locating coiled, encysted larvae in muscle biopsy
  • tx: early stages - thiabendazole, no tx for late stages
20
Q

describe dracunculiasis:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Dracunculus medinensis
  • infection: skin inflammation and ulceration
  • follows drinking water containing intermediate host copepods in which the larvae live
  • ddx: find head of worm in skin lesion or larvae released from a skin lesion following contact with water
  • tx: removing subcutaneous worms by surgery
21
Q

describe loiasis:

  • what worm?
  • describe infection sx?
  • transmission?
  • intermediate host?
  • diagnosis?
  • treatment?
A
  • Loa loa
  • infection: larvae crawl under skin, leaving characteristic tracks; enter eye - visible in subconjunctival space around iris
  • follows by deer fly bites; no animal reservoirs and humans are only definitive host
  • ddx: detection of microfilariae in blood
  • tx: diethylcarbamazine
22
Q

top 5 trematodes (flukes)

A
  • clonorchis sinensis (Chinese or oriental liver fluke)
  • Paragonimus westermani (lung fluke)
  • Schistosoma mansoni (blood fluke)
  • Schistosoma haematobium (blood fluke)
  • Schistosoma japonicum (blood fluke)
23
Q

what are three benzimidazoles on the market?

A
  • mebendazole (first in class)
  • thiabendazole (toxicity limits use)
  • albendazole (useful in GI and tissue infections)
24
Q

benzimidazoles mechanism of action

A
  • binds to tubulin only in helminths

- inhibits formation of microtubules (caps them on plus end, continue to be shortened on minus end)

25
Q

what is the drug of choice for cysticercosis? what is this drug also used to treat?

A

albendazole

  • pinworms
  • hookworms
  • ascariasis
  • trichuriasis
  • strongyloidiasis
26
Q

metabolism of albendazole

A

variable absorption

-rapidly turned into albendazole sulfoxide - active

27
Q

what is mebendazole used for?

A
  • pinworms
  • hookworms
  • ascariasis
  • trichuriasis
28
Q

why is thiabendazole no longer preferred?

A

due to toxicity and potential teratogen

29
Q

what is praziquantel used for?

A

highly effective against cestodes and trematodes
-no activity against nematodes

drug of choice for all schistosomiasis

  • two or three doses yield high cure rates
  • used in mass treatment programs

single dose kills 100% of taenia saginata, taenia solium, and Diphyllo…. latum (but doesn’t kill solium eggs)

30
Q

mechanism of action of praziquantel

A

at low concentrations - increased muscular activity

  • contraction and spastic paralysis
  • worms detach from blood vessel walls
  • migrate from mesenteric veins to the liver

at high concentrations - tegumental damage and exposes a number of tegumental antigens (more effective here)
-clinical effect correlates with tegument changes

may also disrupt calcium homeostasis

31
Q

what is the drug of choice for strongyloidiasis and onchocerciasis?

A

ivermectin

32
Q

what is ivermectin, structurally?

A

a semisynthetic macrocyclic lactone

33
Q

mechanism of action of ivermectin

A
  • paralyzes microfilariae
  • binds to Glu-activated Cl- channels found in nematode nerve or muscle cells
  • causes hyperpolarization by increasing intracellular [Cl-]
  • also binds with high affinity to GABA-gated and other ligand-gated Cl- channels
  • allows host cytotoxic cells to adhere
  • does not kill adult worms, but blocks release of progeny!
34
Q

besides onchocerciasis, what is ivermectin also used for?

A
  • ascariasis
  • enterobiasis
  • strongyloidiasis
  • filariasis
35
Q

what is pyrantel pamoate? what is it used for?

A

broad-spectrum antihelminth

  • available OTC
  • highly effective for treatment of pinworms and ascaris
  • active against adult and immature worms (not against migratory stages or ova)
36
Q

mechanism of action of pyrantel pamoate

A
  • depolarizing neuromuscular blocking agent
  • causes release of ACh and inhibiton of AChE
  • worms are paralyzed and expelled
37
Q

clinical uses of pyrantel pamoate

A
  • ascariasis - one dose is 85-100% effective

- pinworms - 2 doses two weeks apart - 95% cure rate

38
Q

AE of pyrantel pamoate

A

mild and infrequent

39
Q

scabies:
- what causes it?
- infection causes what?
- treatment?

A
  • Sarcoptes scabiei
  • infection: itching dermatosis - female mites burrow superficially beneath the stratum corneum and deposit up to 3 eggs/d; itching and rash from sensitization rxn directed against excreta in burrows
  • tx: permethrin cream (5%) and may need to pretreat with 6% salicylic acid if crusted scabes
40
Q

treatment of lice

A

treat live lice if detected

  • 10 min application of 1% permethrin or pyrethrins
  • requires 2nd application 10d later

chronic infestations - 0.5% malathion

newer pediculicides contain benzyl alcohol, dimethicone, or SPINOSAD

Pharm (19 decks)

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