Pharmacology of GI Infections (Sheehy) Flashcards
Describe metronidazole
prodrug that is active against anaerobic bacteria and anerobic protozoal microorganisms (in class 5-nitroimidazoles)
MOA metronidazole
Dependent on activation by susceptible organisms. Anaerobic organisms with high redox potential will donate electrons to metronidazole. Metronidazole is then able to cause radical-mediated DNA damage to organisms. Can by catalytically recycled
Resistance to metronidazole
increase intracellular O2 levels
Adverse effects metronidazole (2)
1) metallic taste in patient’s mouth
2) disufiram-like effect (induces vomiting if patient drinks EtOH during or 3 days after therapy has ended)
Drugs used for C. diff
1) vancomycin –> severe CD
2) metronnidazole –> mild
3) fidaxomicin –> recurrent CD
how is are C diff drugs administered?
vanco –> oral
metronidazole –> IV
fixamicin –> oral
drugs given for H. pylori infection
1) omeprazole
2) metronidazole
3) tetracycline
4) bismuth salicylate
When is an entamoeba histolytica infection pathogenic?
pathogenic if red blood cells are in the cytoplasm
describe life cycle E. Histolytica
trophozoite –> binucleated precyst –> tetranucleated cyst
E. histolytica: eliminate invading trophozoites (drugs)
Metronidazole
tinidazole
*must be given with luminal amebicide
E. histolytica: eradicate intestinal carriage of the organism (luminal amebicide) drugs
paromomycin
iodoquinol
*no effect on extraintestinal organisms
contraindications iodoquinol
do not use on patients with iodine allergies
What can happen with gastrointestinal invasion of E. histolytica?
goes into portal circulation causing liver abscesses, pulmonary abscesses, and often death
Drugs for giardia
first line –> tinidazole
- metronidazole not approved
- nitazoxanide
Is there blood in stool with giardia?
No
Course of infection cryptosporidium parvum in immune competent vs. immunocompromised patient
immune competent: self-limiting
immunocompromised: severe, life threatening diarrhea, 3-17 liters per day
Drug for C. Parvum
Nitazoxanide
Goal in treatment of immunocompromised patient with Cryptosporidium parvum
restore immune function
Life cycle Nectar americanus/ancyclostoma duodenale (hook worms)
penetrate skin on toes, develop in intestines and eggs excreted in feces
life cycle Ascaris lumbricoides
consume eggs in food, eggs released in feces, but worms stay in the intestine and can lead to obstruction
life cycle strongyloides stercoralis
penetrate skin, release eggs in intestines where they hatch (eggs NOT in stool) can lead to autoinfection or larvae in stool (worse with immunosuppressants)
life cycle trichuris trichiura (whip worm)
injest eggs in food, eggs hatch in intestines and lay more eggs in intestines. No larvae, no transit into intestine wall, no lung involvement, no autoinfection, football eggs in feces
life cycle enterobius vermicularis (pinworm)
eggs ingested and female then migrates and lays eggs at perianal area, hand to mouth transmission by itching (scotch tape test)
primary drug for N. Americanus/A.duodenale
albendazole
primary drugs for A. lumbricoides
albendazole/mebendazole
primary drug for s. sterocoralis
ivermectin
primary drug T. trichiura
mebendazole
primary drugs E. vermicularis
- albendazole
- mebendazole
- pyrantel pamoate
MOA albendazole
inhibits microtubule synthesis to paralyze worms
MOA mebendazole
inhibits microtubule synthesis to paralyze worms
MOA Ivermectin
intensifies GABA transmission in peripheral nerves
MOA thiabendazole
inhibits microtubule synthesis to paralyze worms
MOA pyrantel pamoate
releases ACh and blocks cholinesterase to paralyze worms
MOA praziquantel
increases membrane permeability to Ca2+ resulting in paralysis
MOA niclosamide
uncouples oxidative phosphorylation, blocking glucose uptake, leading to actual death of worm
drug of choice Schistosoma
Praziquantel
drugs for cestodes
- praziquantel
- niclosamide
- albendazole
