91 - GI drugs I Flashcards
Sympathetic stimulation releases a _____ amount of viscid saliva rich in ______; Parasympathetic stimulation releases ________ rich in ________.
small; mucous
copious; amylase
What are the hormones that control acid secretion in an endocrine and paracrine fashion respectively? What cells are involved respectively?
Endocrine:
Gastrin from antral G cells, reach parietal cells (CCK1 receptor) via systemic circulation; and EC-like cells (CCK 2 receptor)
Paracrine:
Histamine, from enterochromaffin-like cells
In cephalic phase, gastric secretion occurs _______ the food enters the oral cavity.
It is stimulated via vagal pathways involving _______and _______ innervation of ganglia in the ________ plexus.
before;
preganglionic;
parasympathetic;
submucosal
In gastric phase, distension or stimulation of _______receptors increases acid via local reflexes.
Sensory
As prostaglandins is protective to the gastric wall, inhibition of ______ will cause an increase incidence of ulcer.
COX 1
arachidonic acid - COX 1 > PG
Which 3 pharmacological classes can stimulate acid secretion? Give example of each class.
- Histamine receptor agonist
- histamine
* as allergy might appear if bound to H1 receptors, H1 receptors needed to be blocked by H1 antagonist: Mepyramine, such that histamine can bind to H2 receptors. - H2 selective agonist
- Betazole
(“Better, So?”) - Gastrin analogue
- Pentagastrin
- similar to c-terminus of gastrin
Which 3 pharmacological classes can reduce acid secretion? Give example of each class.
- M1 antagonist
- pirenzepine - H2 competitive antagonist
- Cimetidine, Ranitidine (Less DDI), Famotidine - Proton pump inhibitor
- Omeprazole, pantoprazole, lansoprazole (potent, irreversible)
How does M1 antagonists like pirenzepine work to reduce acid secretion?
Block acetylcholine on submucosal plexus and myenteric plexuses(M1).
Reduce postganglionic acetylcholine and histamine releases.
- submucosal plexus ganglia have both nicotinic and M1 receptors, but will only block M1
- relieve pain
- low CNS penetration
What effects does H2 competitive like cimetidine and ranitidine bring when it reduces acid secretion?
- It promotes ulcer healing
- it is long acting with high potency (PA2 is around 8)
- also used in treatment for GERD
- also inhibit P450
How does PPI like omeprazole work to reduce acid secretion? Where is it absorbed?
They are absorbed in the duodenum.
- slow acting prodrug
- goes around circulation to reach acidic canaliculi of parietal cells, binds irreversibly to H+/K+-ATPase
- becomes sulphenamide which forms disulphide links with cysteine residue of alpha subunit od H+/K+ pump
- for GERD and Gastrinoma
Name 2 pharmacological classes that protect the mucosal wall.
Give 3 examples of the first class.
Prostaglandin analogue.
- Misoprostol
- Sucralfate
- Carbenoxolone sodium
Long term steroid/ NSAIDS therapy.
Misoprostol A. increases mucus and HCO3- B. decreases blood flow C. decreases acid outflow D. should not be used during pregnancy E. Vomiting is a side effect.
A,C,D
B: should be increases blood flow
E. Diarrhea (mild) is the side effect.
Sucralfate
A. should be taken after meals
B. stimulates prostaglandin and mucous secretion
C. cross links at high pH
D adhere to ulcer site to prevent pepsin attack
B and D
A: given in empty stomach
C: cross links at low pH and then adhere to ulcer site to prevent pepsin attack
What is triple therapy?
What is its purpose and what can it prevent?
Triple therapy =
PPI/ H2 antagonist + 2-3 antibiotics (amoxycillin, clarithromycin, metronidazole) for 2 weeks.
Purpose: heal ulcer
Can prevent recurrence of ulcers.
_____ can be used in quadruple therapy.
It is given in empty stomach, not to mix with food.
Bismuth
