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GI 2 Exam 1 > Pharm - GI Parasites > Flashcards

Pharm - GI Parasites Flashcards

1
Q

gram positive, spore forming, anaerobic rod

- antibiotic-associated pseudomembranous diarrhea and colitis

A

C. difficile

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2
Q

which C. diff toxin is an enterotoxin, causing diarrhea?

A

toxin A

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3
Q

which C. diff toxin is a cytotoxin -> cytotoxic to the colonic cells?

A

toxin B

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4
Q

what does C. diff infection in the colon lead to?

A

red inflamed mucosa with areas of white exudate (pseudomembranes on the surface) of the large intestine

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5
Q

what antibiotics are frequently associated with C. diff infection?

A
  • fluoroquinolones
  • clindamycin
  • cephalosporins
  • penicillins
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6
Q

what antibiotics are rarely associated with C. diff infection, and thus can be used as treatment?

A
  • vancomycin
  • metronidazole
  • fidaxomicin
  • NOTE: aminoglycosides, tetracyclines mentioned on table
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7
Q

what is the preferred treatment for severe C. diff infection?

A

vancomycin

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8
Q

what is the preferred treatment for mild C. diff infection?.

A

metronidazole

  • has disulfrum-like effect (pt will throw up if taken with alcohol) KNOW THIS
  • also causes metallic-taste in mouth
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9
Q

what is the preferred treatment for recurrent C. diff infection?

A

fidaxomicin

- spares many anaerobic colonic flora

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10
Q

what is the most common cause of duodenal ulcers ad chronic gastritis?

A

H. pylori

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11
Q

what are the key drugs used to treat H. pylori infection?

A
  • omeprazole (PPI)
  • metronidazole
  • tetracycline
  • bismuth subsalicylate
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12
Q

“classic amoeba”

- trophozoites invade intestinal mucosa -> portal blood circulation -> liver abscesses

A

Entamoeba histolytica

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13
Q

what is the life cycles of entamoeba histolytica?

A

trophozoite -> binucleated precyst -> tetranucleated cyst (what is pathogenic)

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14
Q

what drugs are used to eliminate the invading trophozoites?

A

metronidazole or tinidazole

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15
Q

what drugs are used to eradicate intestinal carriage of the organism (luminal amebicide)

A
  • *paromomycin** or iodoquinol

- no effect on extraintestinal organisms

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16
Q

when would you use luminal amebicide agents?

A

for asymptomatic carriers (cysts or trophozoites without internalized red blood cells in the cytoplasm)

NOTE: both metronidazole and tinidazole still given with luminal amebicide, to ensure eradication of infection)

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17
Q

what luminal amebicide is contraindicated in a patient with an iodine allergy/sensitivity?

A

iodoquinol

- used as luminal amebicide, no effect against extraintestinal organisms

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18
Q

what is the MOA of iodoquinol?

A

halogenated hydroxyquinoline

- 90% is retained in the intestine and excreted in the feces

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19
Q

what are the adverse effects of iodoquinol?

A

diarrhea, anorexia, nausea, vomiting, abdominal pain, headache, rash, pruritis

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20
Q

kite-shaped trophozoite, 5% of US adults and infected (mostly asymptomatic)

  • coat small intestine, interfering with fat absorption
  • do NOT invade the intestinal wall -> do NOT cause bloody stool
  • gassy, frothy diarrhea
  • must examine stool for cytst
A

giardia lamblia

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21
Q

what are the pharmacological agents used to treat giardia lamblia?

A

tinidazole (first line agent)

- or nitazoxanide

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22
Q

this drug inhibits the pyruvate-ferredoxin oxidoreductase enzyme (which is essential to anaerobic energy metabolism)
- is a prodrug, what is it’s active metabolite?

A

nitazoxanide
- active metabolite is tizoxanide

  • rapidly absorbed, excreted in urine and feces
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23
Q

what are the adverse effects of nitazoxanide?

A

nausea, anorexia, flatulence, increased appetite, enlarged salivary glands, yellow eyes, dysuria, bright yellow urine

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24
Q

oocyst with 4 motile sporozoites

  • life cycle occurs within intestinal epithelial cells (causing diarrhea and abdominal pain)
  • self limiting if immunocompetent
  • can be life threatening if immunocompromised (3-17 L/day)
A

cryptosporidium parvum

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25
Q

what is the treatment for cryptosporidium parvum?

- antidiarrheal AND antimicrobial

A
  • antidiarrheal: loperamide (Sheehy’s favorite, the failed opioid that’s just a diarrhea med now)
  • antimicrobial: nitazoxanide (preferred), or paromomycin
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26
Q

what drug therapy is given for cryptosporidium parvum treatment in HIV patients?

A

antiretroviral therapy + nitazoxanide

- the main goal is to restore immune function

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27
Q

usually macroscopic helminth (dx requires visualization of microscopic eggs in feces)
- no immune response to worms, but response to dead worms and eggs (elevation of eosinophils)

A

nematodes

28
Q

nematode that penetrates bare skin between toes

- larvae travel to lungs (alveoli) -> grow, are coughed up and swallowed -> adult worms dvlp in small intestine

A

necator americanus and ancylostoma duodenale (hook worms)

29
Q

worm eggs excreted in feces -> larvae penetrate intestine and travel to lung -> larvae grown, are coughed up, and swallowed -> worms dvlp in small intestine -> release fertilized eggs in fecels

A

ascaris lumbricoides

30
Q

larvae in soil, penetrates human skin, travels to lungs -> larvae grow in lungs -> coughed up and swallowed -> EGGS ARE NOT PASSED IN STOOL!!!

A

strongyloides stercoralis

- hatched larvae can autoinfect, extrete in feces -> infect, or excrete in feces, lay eggs, and new larvae -> infect

31
Q

vomiting, abdominal bloating, diarrhea, anemia, wt loss

  • immunospuuressive medications can lead to severe auto-infection
  • dx: larvae in feces, enterotest
A

strongyloides stercoralis

32
Q

simple life cycle: ingestion of food with infective eggs -> eggs hatch in small intestine, migration to cecum and ascending large intestine -> mature adult produces thousands of eggs per day for 1 year
- NO LARVAE, NO TRANSIT THROUGH INTESTINAL WALL, NO LUNG INVOLVEMENT, NO EOSINOPHILIA, NO AUTO-INFECTION!

A

trichuris trichiura (whip worm)

33
Q

which worm has football shaped eggs?

A

trichuris trichura

34
Q

eggs ingested, pinworms mature in cecum and ascending colon -> female migrates to perianal area (at night to lay eggs) -> eggs infectious 4-6 hours later

  • severe perianal itching -> hand-mouth transmission
  • no eosinophilia
A 
enterobius vermicularis (pinworm)
- SCOTCH TAPE TEST!
35
Q

what are the two broad spectrum oral anti-heminthic agents?

A

albendazole and mebendazole

- (worms are bendy!)

36
Q

what is the MOA of albendazole and mebendazole?

A

inhibit microtubule synthesis, paralyzing worms -> worms passed in stool
- are prodrugs, active metabolite produced after the first pass effect

37
Q

what are the pharmacokinetics of thiabendazole?

A

rapidly absorbed after ingestion, largely excreted in urine, can be absorbed from the skin
- NOTE: same MOA as albendazole/mebendazole (just diff side groups)

38
Q

what are the adverse effects of thiabendazole?

A

dizziness, anorexia, nausea, vomiting
- irreversible liver failure, fatal Stevens-Johnson syndrome

NOTE: much more toxic than albendazole/mebendazole (so it isn’t used much!)

39
Q

what is the MOA of ivermectin?

A

intensifies y-aminobutyric acid (GABA)-mediated transmission of signals in peripheral nerves of the nematode

40
Q

rapidly absorbed, oral only, wide distribution, excretion in feces

  • adverse effects are uncommon
  • should not be combined with other drugs that enhance GABA activity (barbituates, benzodiazepines, valproid acid)
A

ivermectin

41
Q

neuromuscular blocking agent, causes release of acetylcholine and inhibits cholinesterase

  • results in paralysis and expulsion of the nematode
  • poorly absorved from GI tract, half administered dose recovered unchanged in feces
  • infrequent/transient adverse effects
A

pyrantel pamoate

42
Q

albendazole is the primary drug for which 3 worms?

A
  • n. americanus/ a.duodenale
  • a. lumbricoides
  • e. vermicularis
43
Q

mebendazole is the primary drug for which 3 worms?

A
  • a. lumbricoides
  • t. trichiura
  • e. vermicularis
44
Q

ivermectin is the drug of choice for which worm?

A

s. stercoralis

45
Q

pyrantel pamoate in the drug of choice for which worm?

A

e. vermicularis

46
Q

what are the 3 primary drugs used to treat e. vermicularis?

A
  • albendazole
  • mebendazole
  • pyrantel pamoate
47
Q

what are the 2 primary drugs used to treat a. lumbricoides?

A
  • albendazole

- mebendazole

48
Q

these worms are extremely common worldwide, found in fresh water
- invade venous system through exposed skin -> eggs must reach fresh water to hatch -> adult worms are able to survive and release eggs for years (NOT killed by immune system -> molecular mimicry)

A

schistosoma spp (blood flukes)

49
Q

where are S. japonicum worms found?

  • where do they reside?
  • where do they deposit eggs?
A

Eastern Asia

  • intestinal tract
  • feces
50
Q

where are S. mansoni worms found?

  • where do they reside?
  • where do they deposit eggs?
A

South America and Africa

  • intestinal tract
  • feces
51
Q

where are S. haematobium worms found?

  • where do they reside?
  • where do they deposit eggs?
A

Africa

  • bladder
  • urine
52
Q

eggs hatch in fresh water, larvae infect and mature within a snail -> infect humans (exposed skin) -> mate in intrahepatic portion of portal venous system -> migrate to veins surrounding intestine of bladder to lay eggs -> eggs enter the lumen of intestine or bladder to be excreted

A

schistosoma spp (blood flukes)

53
Q

dermatitis (immediate), Katayama fever (fever, hives, bronchospasm, hepatosplenomegaly 4-8 weeks later), chronic fibrosis (d/t egg deposits that don’t make it to bladder)

A

schistosoma spp.

54
Q

what is the treatment for schistosoma?

A

praziquantel

55
Q

what is the MOA of praziquantel?

A

increases the permeability of nematode and cestode cell membrane to calcium -> paralysis, dislodgment, and death

56
Q

what are the pharmackoinetics of praziquantel?

A

oral administration, rapidly absorbed, excreted mainly by the kidneys

57
Q

what are the adverse effects of praziquantel?

A

headache, dissiness, drowsiness, fatigue (drug’s fault)

- after several days: low grade fever, pruritis, skin rash (dead worm’s fault, body clearing infection)

58
Q

acquired by ingestion of undercooked pork containing larvae

  • attaches via hooks
  • diagnosed by proglottids and/or eggs in feces
A

taenia solium

59
Q

acquired by ingestion of indercooked beef

  • attaches via suckers
  • diagnosed by proglottids and/or eggs in feces
A

taenia saginata

60
Q

pigs/cows ingest eggs from field contaminated with human feces -> larvae disseminate through intestine into muscle of the aminal -> larvae develop into cysticerci -> humans inject undercooked meat -> tapeworm matures in intestine

A

taenia solium and taenia saginata

- clinically manifests as weight loss nad malnutrition

61
Q

acquired by ingesting larvae in raw freshwater fish

  • adult tape worm in human ingestion excretes gradis proglottids with eggs -> eggs hatch in water and convert to motile larvae -> ingested by human
  • dx by proglottids and eggs in feces
A

diphyllobothrium latum

- few abdominal symptoms, worm absorbs vitamin B12 (anemia)

62
Q

extra-intestinal tapeworm infection
- dogs and sheep perpetuate the life cycle with a human acting as a dead end: humans ingest eggs from dog feces -> eggs hatch in intestine and larva form hydatid cysts

A

echinoccus granulosus

63
Q

what 3 drugs are used for cestode treatment?

A
  • praziquantel
  • niclosamide
  • albendazole
64
Q

what is unique about niclosamide?

A

it is the only drug that KILLS (rather than paralyzing) the worm
- but it isn’t used often d/t side effects, long duration of therapy, and limited availability

65
Q

what is the MOA of niclosamide?

A

uncouples oxidative phosphorylation, blocking uptake of glucose
- not effective against hydatid cysts

GI 2 Exam 1 (22 decks)

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