GI system from Pharm perspective

Question 1

Sympathetic role in GI

Answer 1

relaxes walls at a2, B2

Contracts sphincters at a1

Question 2

Parasympathetic role in GI

Answer 2

Contracts walls, relaxes sphincters, increases secretions all at M3

Question 3

What is the predominant tone in GI tract?

Answer 3

parasympathetic

Question 4

dopamine role in GI

Answer 4

modulatory transmitter in ENS. Direct relaxant effect by activating D2 receptors in LES and fundus and antrum. Inhibits Ach release from intrinsic cholinergic neurons by activating pre-junctional D2 receptors

Question 5

serotonin role in GI

Answer 5

An important transmitter or cotransmitter at excitatory neuron-neuron junctions in ENS (too much=diarrhea)

Question 6

Opiate role in GI

Answer 6

present in some secretomotor and interneurons in ENS–> gastroparesis. Inhibit Ach release and peristalsis. May stimulate secretion.

Question 7

Compare and contrast IBS and IBD and recall treatments

Answer 7

IBS: no physical damage. Treat prevailing symptoms. Due to waxing/waning treat with PARTIAL serotonin agonist like tegaserod. TNF and interleukins play a role
IBD: TNFa has pivotol role, tx with TNFa antibodies–> infliximab (start first with glucocorticoids, if refractory then go on to infliximab)

Question 8

Describe the tx of opiate induced GI dysfunction

Answer 8

Write prescription for narcotic+laxative. Judicial use of opiate antogonists.

Question 9

AE of octreotide

Answer 9

paradoxical fatty diarrhea

Question 10

Describe pill-induced esophagitis

Answer 10

usually in older patients (produce less saliva), instructions will say to sit up for a certain amount of time like bisphosphonates, often seen with ER and gel capsule drugs

Question 11

Explain the role of P-gp and CYP3A in drug bioavailability

Answer 11

Decreased P-gp activity causes increased bioavailability.

CYP3A may be controlled by P-gp

Question 12

Compare and contrast the effects of antacids, H2, and PPIs on concurrent meds

Answer 12

All 3 increase pH–> decrease in bioavailability of antiretrovirals
Antacids chelate drugs like doxycycline, tetracycline, fluroquinolones
H2 and PPIs can inhibit CYP activity
- H2: cim inhibits 1A2, 2D6, 2C19, 3A4; fam decreases theophylline clearance
- PPIs: substrates for CYP2C19, decrease effectiveness of clopidogrel