Pharm - GI Infections Flashcards
compare effects of toxin A and toxin B in c. diff
toxin A: diarrhea
toxin B: cytotoxic to colonic cells
what are the antibiotics frequently associated with c. diff
- fluoroquinolones
- clindamycin
- later gen cephalosporins
- later gen penicillin
preferred tx for severe, mild, and recurrent c. diff infection
severe: vancomycin
mild: metronidazole
recurrent: fidaxomicin
compare administration b/w vancomycin and metronidazole when treating c. diff
vancomycin: oral
metronidazole: IV or oral; used if oral administration won’t work
what are the families of the three main drugs used to treat c. diff
vancomycin: glycopeptide
metronidazole: 5-nitroimidazole
fidaxomicin: macrolide
when treating e. histolytica, what are the drugs used to:
1) eliminate invading trophozoites
2) eradicate intestinal carriage of the organism
eliminate invading trophozoites: metronidazole or tinidazole
eradicate intestinal carriage of organism: paromomycin or iodoquinol
how to treat asymptomatic carriage of e. histolytica
luminal amebicide
what is the drug of choice for extraluminal amebiasis with e. hystolytica
metronidazole
what must you give with metronidazole or tinidazole when eradicating e. histolytica
luminal amebicide
adverse effects iodoquinol
diarrhea, anorexia, N/V, abd pain, HA, rash, pruritis
what is iodoquinol used for and why
used as a luminal amebicide
- 90% retained in intestine and excreted in feces, so good for treating intraintestinal organisms
what families are paromomycin and iodoquinol in
paromomycin: aminoglycoside
iodoquinol: 8-hydroxyquinolines
first line agent for treating giardia lamblia
- 2nd and 3rd line agents
first line: tinidazole
then nitazoxanide and metronidazole
MOA nitazoxanide
inhibition of pyruvate-ferredoxin oxidoreductase enzyme (which is essential to anaerobic energy metabolism)
- it’s a prodrug
adverse effects nitazoxanide
nausea, anorexia, flatulence, increased appetite, enlarged salivary glands, yellow eyes, dysuria, bright yellow urine
what antidiarrheal and antimicrobial agents are used to treat cryptosporidium parvum
antidiarrheal: loperamide
antimicrobial: nitazoxanide (preferred) and paromomycin
compare treatment for cryptosporidium parvum between HIV patients and otherwise-immunocompromised patients
HIV: antiretroviral therapy + nitazoxanide
other: reduce dose of immunosuppressant + nitazoxanide
diagnosis for nematodes requires ______
visualization of microscopic eggs in feces
describe life cycle of necator americanus and ancylostoma duodenale (hook worms)
penetrates skin in between toes –> larvae travel to lungs –> coughed up and swallowed –> adult worms develop in small intestine –> worms repopulate and release eggs –> eggs excreted in feces –> eggs hatch and larvae live in soil
describe the life cycle of ascaris lumbricoides
consumption of eggs in contaminated food –> larvae penetrate intestine and travel to lung –> coughed up and swallowed –> adult worms develop in small intestine –> worms release eggs –> eggs excreted in feces –> eggs hatch and larvae live in soil
describe the life cycle of strongyloides stercoralis
larvae in soil penetrate human skin –> travels to lungs –> coughed up and swallowed –> mature worms form in small intestine and release eggs –> eggs hatch in intestine (EGGS DO NOT PASS IN STOOL) –> larvae can autoinfect, excrete in feces and infect, or excrete in feces, mature, lay eggs, and new larvae infect
what medications can lead to severe autoinfection with strongyloides stercoralis
immunosuppressive meds
- prednisone in asthma patients
how to diagnose strongyloides stercoralis
larvae in feces and enterotest
describe the life cycle of trichuris trichiura (whip worm)
ingestion of food with infective eggs –> eggs hatch in small intestine –> migrate to cecum and ascending large intestine –> mature adult produces thousands of eggs per day for 1 year
how to diagnose trichuris trichiura (whip worm)
eggs in feces (football shaped)
describe the life cycle of enterobius vermicularis (pinworm)
eggs ingested –> pinworms mature in cecum and ascending large intestine –> females migrate to perianal area at night to lay eggs
what are the 5 nematode tx drugs
1) albendazole
2) mebendazole
3) thiabendazole
4) ivermectin
5) pyrantel pamoate
MOA albendazole, mebendazole, and thiabendazole
inhibits microtubule synthesis which PARALYZES the worms which are then passed in the stool
- a prodrug
compare adverse effects b/w thiabendazole and abendazole and mebendazole
thiabendazole is much more toxic, causes:
- dizziness
- anorexia
- N/V
- can cause irreversible liver failure and stevens johnson syndrome
MOA ivermectin
intensifies y-aminobutyric acid (GABA)-mediated transmission of signals in peripheral nerves of the nematode –> causing PARALYSIS
administration of ivermectin
oral only
MOA pyrantel pamoate
neuromuscular blocking agent causing release of ACh and inhibition of cholinesterase –> causing PARALYSIS
pharmacokinetics pyrantel pamoate
poorly absorbed in GI tract (stays in GI), half of administered dose recovered unchanged in feces
primary, alternative, and poor choice of drugs to treat N. americanus and A. duodenale
primary: albendazole
alternative: mebendazole or pyrantel pamoate
poor: ivermectin
primary and alternate tx for A. lumbricoides
primary: albendazole or mebendazole
alternate: ivermectin
primary and alternate tx for S. stercoralis
primary: ivermectin
alternate: albendazole
primary, alternate, and second alternate tx for T. trichiura
primary: mebendazole
alternate: albendazole
second alternate: ivermectin
primary tx for E. vermicularis
primary: albendazole, mebendazole, and pyrantel pamoate
how to schistosoma mansoni trematodes infect
invade venous system through exposed skin
- eggs must reach fresh water to hatch
describe geographic distribution of S. japonicum, S. mansoni, and S. haematobium (schistosoma spp)
S. japonicum: east asia
S. mansoni: south america and africa
S. haematobium: africa
describe where the organisms reside in S. japonicum, S. mansoni, and S. haematobium (schistosoma spp)
S. japonicum: intestinal tract
S. mansoni: intestinal tract
S. haematobium: bladder
describe where the organism deposits eggs in S. japonicum, S. mansoni, and S. haematobium (schistosoma spp)
S. japonicum: feces
S. mansoni: feces
S. haematobium: urine
describe the life cycle of schistosoma spp. (blood flukes)
eggs hatch in fresh water –> larvae infect and mature within a snail –> mature larvae leave snails and infect humans through exposed skin –> mate in intrahepatic portion of portal venous system –> migrate to veins surrounding intestine or bladder to lay eggs –> eggs enter lumen of intestine or bladder
tx of choice for schistosoma
praziquantel
MOA praziquantel
increases permeability of nematode and cestode cell membranes to calcium –> cause PARALYSIS
adverse effects praziquantel
immediate: HA, dizziness, drowsiness (all from drug)
after several days: low grade fever, pruritis, skin rash (all from dead worm)
describe life cycle of Taenia solium and Taenia saginata
pigs/cows ingest egg from field contaminated by human feces –> larvae disseminate through intestine into muscle –> larvae develop into cysticerci –> human ingests undercooked meat –> tapeworm matures in intestine
compare T. solium and T. saginata in how they infect
T. solium: hooks
T. saginata: suckers
life cycle of diphyllobothrium latum
adult tape worm in human ingestion excretes proglottids w/ eggs –> eggs hatch in water and convert to motile larvae –> ingested by human
how does echinococcus granulosus infect
humans ingest eggs from dog feces –> eggs hatch in intestine and larva form hydatid cysts
tx for cestodes (tapeworms)
praziquantel, niclosamide, albendazole
MOA niclosamide
uncouples oxidative phosphorylation, blocking uptake of glucose –> results in DEATH of parasite
why is niclosamide an alternative tx for tapeworms
it is not effective against hydatid cysts
