GI drugs pg 372 and bile/bilirubin physio

Question 1

osmotic laxatives: examples and mechanism

Answer 1

lactulose, polyethylene glycol (magnesium hydroxide, magnesium citrate). they provide an osmotic load to draw water out. lactulose also treats hepatic encephalopathy since gut flora degrade it into metabolities that promote nitrogen excretion as NH4+

Question 2

infliximab: mechanism, use, toxicity

Answer 2

monoclonal antibody against TNF-alpha.
used in ankylosing spondilitis, ulcerative colitis, crohn disesae, psoriasis, rheumatoid arthritis
toxicity: fever, hypotension, infection INCLUDING REACTIVATION of TB

Question 3

sulfasalazine: mechanism and use

Answer 3

used for crohn and ulcerative colitis.
combination of sulfapyridine (antibiotic) and 5-aminosalicylic acid (anti-inflammatory). activated by colonic bacteria
used for crohn disease and ulcerative colitis

Question 4

sulfasalazine toxicity

Answer 4

malasie, nasuea, sulfonamide toxicity, oligospermia (reversible)

Question 5

ondansetron: mechanism and use.

Answer 5

5-HT antagonist and centrally-acting anti-emetic. decreases vagal stimulation. used for severe nausea and vomiting, as is seen in cancer patients or post-op.

Question 6

metoclopramide mechanism and use

Answer 6

this is a D2 receptor antagonist that increaess resting tone, contractility, LES tone, and motility. it doesn’t effect colonic transport time.
it is good for diabetic and post-surgerical gastroparesis, and is also an anti-emetic.

Question 7

metoclopramide toxicity

Answer 7

increases parkinsonian effects. interacts with digoxin and diabetic agents. contraindicated in pts with small bowel obstruction or parkinson disease.
(also caues restlessness, drowsiness, fatigue, depression, nausea, diarrhea).

Question 8

Describe the bilirubin pathway

Answer 8

RBCs –> heme –> unconjugated/indirect bilirubin. Unconjugated bilirubin is not water soluable, so it must circulate in the blood bound to albumin. It is then delivered to the liver, where UDP gucuronosyl transferase converts it to soluable, conjugated bilirubin (conjugated with glucuronic acid). conjugated bilirubin is delivered to the gut. gut bacteria convert it to urobilinigin. most urobilinigen stays in the gut and is converted to brown stercobilin. some urobilinogen goes back to the bloodstream. the kidney may excrete it in its yellow urobilin form.

Question 9

Where are Peyers patches located? What do they do? What kinds of cells do they contain?

Answer 9

lamina propria and submucosa of the ileum. they contain M cells, which present antigen to immune cells. they are unencapsulated lymph tissue. When B cells are stimulated in the germinal center of the peyer patches, they mature to make secretory IgA antibodies.

Question 10

What are the functions of bile?

Answer 10

1. fat digestion and absorption; also critical for fat soluble vitamins
2. only way for the body to actively excrete cholesterol
3. antimicrobial activity via membrane disruption.

Question 11

What is the most important enzyme in bile synthesis?

Answer 11

cholesterol 7-alpha hydroxylase