Pharmacology of GI Infections

Question 1

What 3 drugs can capable of treating C. Difficile?

What are their classes?

Answer 1

Vancomycin - glycopeptide
Metronidazole - 5-nitroimidazole
Fidaxomicin - macrolide

Question 2

In what severity of CDI would Vancomycin be used?

What other level of severity will it treat?

Answer 2

Severe CDI - first line treatment for CDI

Mild CDI - equivalent to metronidazole

Given PO

Question 3

In what severity of CDI would Metronidazole treat?

Answer 3

If PO route won’t work for the pt.

Given PO or IV

Question 4

In what case would you give Fidaxomicin for CDI? Why?

Answer 4

Recurrent CDIs - Spares many anaerobic colonic flora

Question 5

What is the life cycle of E. histolytica?

Answer 5

Trophozoite -> binucleated precyst -> tetranucleated cyst

Question 6

What are the 2 therapeutic goals of treating E. histolytica and which drugs can assist in those goals?

Answer 6

1. Eliminate the invading trophozoites - Metronidazole or Tinidazole
2. Eradicate the intestinal carriage (the bug within the lumen) - Paromomycin or Iodoquinol

Question 7

To ensure eradication of E. histolytica, metronidazole and tinidazole must be given with…

Answer 7

A luminal amebicide (Paromomycin or Iodoquinol). If not, the intraluminal bugs will just re-infect.

Question 8

MOA of Iodoquinol

PKs

Which patients should cautioned about taking?

Answer 8

Unknown

90% retained in the intestine - good because we are treating the intraluminal bug

I- sensitivities

Question 9

What is the major type of treatment given in a Giardia?

What is the first line Rx treatment?

What are 2 other options?

Answer 9

Supportive - correct fluid and E- abnormalities

Tinidazole

Metronidazole, Nitazoxanide

Question 10

MOA of Nitazoxanide

What is unique about it?

Adverse effects?

Answer 10

Inhibition of pyruvate-ferrodoxin oxidoreductase enzyme

It is a prodrug

Flatulence, enlarged salivary glands, yellow eyes/urine

Question 11

What drugs are given to treat Cryptosporidium parvum caused:

Diarrhea
Antimicrobial agents
Fluid management (none)

Answer 11

Anti-diarrheal: Loperamide

Anti-microbial agents: Nitazoxanide (preferred), Paromomycin

Question 12

In a patient with HIV and a C. parvum infection, what should be given?

Answer 12

Antiviral therapy + nitazoxanide

Question 13

Where does the life cycle of C. parvum occur?

Answer 13

Within intestinal epithelial cells

Question 14

What class does nitazoxanide belong to?

What class does paromomycin belong to?

Answer 14

Nitazoxanide: no class

Paromomycin: aminoglycoside

Question 15

Life cycle of Necatur americanus and Ancylostoma (hookworms)?

What other parasite has the same life cycle?

Answer 15

Penetrates skin between toes
Larvae travel to lungs (alveoli)
Larvae grow and are coughed up and swallowed
Adult worms develop in SI
Worms populate and release fertilized eggs
Eggs excreted in feces
Eggs hatch and larvae live in skin

Ascaris lumbricoides

Question 16

Life cycle of Strongyloides stercoralis

Answer 16

Larvae in soil penetrates skin and travels to lungs
Larvae grow in lungs, are coughed up and swallowed to the SI
Mature worms produce eggs
Eggs DO NOT get passed in stool - can create an autoinfection!

Question 17

In which patients may you see a severe auto-infection of Strongyloides infection?

Answer 17

Pts. on immunosuppressant meds - on prednisone and asthma

Question 18

What is unique about the life cycle of Trichuris trichuria?

Answer 18

No larvae, no transit through the intestinal wall, no lung involvement, no eosinophilia, no auto-infection

Question 19

Life cycle of Enterobius vermicularis

Answer 19

Eggs ingested, pinworms mature in the cecum and ascending colon
Females migrate to the perianal region to lay eggs (at night)

Question 20

What drug has the most adverse effects of nematode treatment drugs?

Answer 20

Thiabendazole

Question 21

The majority of anti-parasitic drugs eliminate pathogens by…

Answer 21

Paralysis of bugs - relies on pts. immune system to help clear it

Question 22

Primary treatment of N. americanus and A. duodenale

Answer 22

Albendazole

Question 23

Primary treatment of A. lumbircoides (2)

Answer 23

Albendazole

Mebendazole

Question 24

Primary treatment of S. stercoralis

Answer 24

Ivermectin

Question 25

Primary treatment of T. trichiura

Answer 25

Mebendazole

Question 26

Primary treatment of E. vermicularis (3)

Answer 26

Albendozole
Mebendozole
Pyrantel pamoate

Question 27

How does Schistosoma spp. invade humans?

Answer 27

Through intact skin!

Eggs must reach freshwater to hatch - adults may survive and release eggs for years

Question 28

What is the treatment for Schistosoma?

Answer 28

Praziquantel

Question 29

Praziquantel MOA

Answer 29

Paralysis - causes increased Ca++ permeability of worms’- CM

Immediate: headache, dizziness, drowsiness, lassitude
After a few days: low grade fever, pruritis, rash

Question 30

What is the life cycle of cestodes (tapeworms)?

Answer 30

Pigs/cows ingest egg from field contaminated w/ human feces

Human ingests undercooked meat, tape worm matures in intestines

Question 31

Where does D. latum live?

Answer 31

Raw freshwater fish

Question 32

Echinococcus granulosus comes from…

What are formed in the intestined?

Answer 32

Dogs/sheep - ingested from their feces

Hyatid cysts

Question 33

What 3 drugs are used for cestode therapy?

Answer 33

Praziquantel
Niclosamide
Albendazole

Question 34

What is the only anti-parasitic will kill the bug, rather than paralysis?

Answer 34

Niclosamide - uncouples oxidative phosphorylation

Question 35

Adverse effects of Metronidazole

Answer 35

GI sx
HA
Metallic taste**
Do not take w/ EtOH - will cause it to be vomited