Pharmacology of GI Infections (Sheehy)

Question 1

Describe metronidazole

Answer 1

prodrug that is active against anaerobic bacteria and anerobic protozoal microorganisms (in class 5-nitroimidazoles)

Question 2

MOA metronidazole

Answer 2

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

Question 3

Resistance to metronidazole

Answer 3

increase intracellular O2 levels

Question 4

Adverse effects metronidazole (2)

Answer 4

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)

Question 5

Drugs used for C. diff

Answer 5

1) vancomycin –> severe CD
2) metronnidazole –> mild
3) fidaxomicin –> recurrent CD

Question 6

how is are C diff drugs administered?

Answer 6

vanco –> oral
metronidazole –> IV
fixamicin –> oral

Question 7

drugs given for H. pylori infection

Answer 7

1) omeprazole
2) metronidazole
3) tetracycline
4) bismuth salicylate

Question 8

When is an entamoeba histolytica infection pathogenic?

Answer 8

pathogenic if red blood cells are in the cytoplasm

Question 9

describe life cycle E. Histolytica

Answer 9

trophozoite –> binucleated precyst –> tetranucleated cyst

Question 10

E. histolytica: eliminate invading trophozoites (drugs)

Answer 10

Metronidazole
tinidazole
*must be given with luminal amebicide

Question 11

E. histolytica: eradicate intestinal carriage of the organism (luminal amebicide) drugs

Answer 11

paromomycin
iodoquinol

*no effect on extraintestinal organisms

Question 12

contraindications iodoquinol

Answer 12

do not use on patients with iodine allergies

Question 13

What can happen with gastrointestinal invasion of E. histolytica?

Answer 13

goes into portal circulation causing liver abscesses, pulmonary abscesses, and often death

Question 14

Drugs for giardia

Answer 14

first line –> tinidazole

• metronidazole not approved
• nitazoxanide

Question 15

Is there blood in stool with giardia?

Answer 15

No

Question 16

Course of infection cryptosporidium parvum in immune competent vs. immunocompromised patient

Answer 16

immune competent: self-limiting

immunocompromised: severe, life threatening diarrhea, 3-17 liters per day

Question 17

Drug for C. Parvum

Answer 17

Nitazoxanide

Question 18

Goal in treatment of immunocompromised patient with Cryptosporidium parvum

Answer 18

restore immune function

Question 19

Life cycle Nectar americanus/ancyclostoma duodenale (hook worms)

Answer 19

penetrate skin on toes, develop in intestines and eggs excreted in feces

Question 20

life cycle Ascaris lumbricoides

Answer 20

consume eggs in food, eggs released in feces, but worms stay in the intestine and can lead to obstruction

Question 21

life cycle strongyloides stercoralis

Answer 21

penetrate skin, release eggs in intestines where they hatch (eggs NOT in stool) can lead to autoinfection or larvae in stool (worse with immunosuppressants)

Question 22

life cycle trichuris trichiura (whip worm)

Answer 22

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

Question 23

life cycle enterobius vermicularis (pinworm)

Answer 23

eggs ingested and female then migrates and lays eggs at perianal area, hand to mouth transmission by itching (scotch tape test)

Question 24

primary drug for N. Americanus/A.duodenale

Answer 24

albendazole

Question 25

primary drugs for A. lumbricoides

Answer 25

albendazole/mebendazole

Question 26

primary drug for s. sterocoralis

Answer 26

ivermectin

Question 27

primary drug T. trichiura

Answer 27

mebendazole

Question 28

primary drugs E. vermicularis

Answer 28

• albendazole
• mebendazole
• pyrantel pamoate

Question 29

MOA albendazole

Answer 29

inhibits microtubule synthesis to paralyze worms

Question 30

MOA mebendazole

Answer 30

inhibits microtubule synthesis to paralyze worms

Question 31

MOA Ivermectin

Answer 31

intensifies GABA transmission in peripheral nerves

Question 32

MOA thiabendazole

Answer 32

inhibits microtubule synthesis to paralyze worms

Question 33

MOA pyrantel pamoate

Answer 33

releases ACh and blocks cholinesterase to paralyze worms

Question 34

MOA praziquantel

Answer 34

increases membrane permeability to Ca2+ resulting in paralysis

Question 35

MOA niclosamide

Answer 35

uncouples oxidative phosphorylation, blocking glucose uptake, leading to actual death of worm

Question 36

drug of choice Schistosoma

Answer 36

Praziquantel

Question 37

drugs for cestodes

Answer 37

• praziquantel
• niclosamide
• albendazole