GI

Question 1

How is acid secreted into gastric lumen?

Answer 1

AcH, Histamine, Prostaglandin, and Gastrin bind to their receptors on the membrane of parietal cell. AcH and gastrin mobilize Ca+ which triggers proton pump. Histamine and prostaglandins activate adenylyl cyclase, increase cAMP, which activates protein kinase and proton pump. Histamine is most important and final mediator of gastric acid secretion

Question 2

Omeprazole

Answer 2

Proton pump inhibitor. Prevents parietal cell proton pump from transporting H+ into the lumen of the stomach. Gastric motility is not affected.
Acts as a prodrug, releses drug when pH is >6.
Irreversible inhibitor
Superior to H2 blockers in treatment of reflux esophagitis
Administer more than 3 hrs prior to anesthesia
Tx for Zollinger Ellison syndrome
May affect absorption of Ca+ carbonate
Affects cytochrome P450 metabolism

Question 3

Misoprostol

Answer 3

Prostaglandin/PPI.
Inhibit cAMP production and therefore acid secretion. It is thought that ulcers may be d/t decreased amounts of prostaglandins
Contraindicated in pregnancy
SE: diarrhea, nausea

Question 4

Hyoscine butylbromide, Propantheline bromide, Dicyclomine hydrochloride

Answer 4

Antimuscarinics
Inhibit AcH from binding to parietal receptors thereby decreasing cyctosolic Ca+ and histamine release, reducing acid secretion by parietal cells
SE’s dry mouth, pupillary dilation, urinary urgency and retention

Question 5

Sodium Bicarb

Answer 5

Antacid
Rapid, brief action
Systemic alkalosis is possible
Fluid retention
Useful to alkalinize the urine
Increased Na+ load may not be tolerated in CHF or heart disease

Question 6

Mg hydroxide

Answer 6

Antacid
Not associated with acid rebound
May cause diarrhea
May cause neurologic, meuromuscular, and CV impairment in pt with renal dysfunction

Question 7

Ca+ carbonate

Answer 7

Antacid
Chronic use causes metabolic alkalosis
Hypercalcemia may occur with renal disease
Can get acid rebound
may cause gas

Question 8

Aluminum hydroxide

Answer 8

Causes slowing of gastric emptying and marked constipation
Unpleasant taste
Hypophosphatemia can occur

Question 9

Complications and interactions of antacids

Answer 9

Chronic alkalinization may increase susceptibility to acid-sensitive bacilli
Acid rebound (by Ca+ containing antacids)
Milk alkali syndrome
Phosphorus depletion (Aluminum)
Hasten delivery of drugs to small intestine
Decrease bioavailibility of oral cimetidine
Increase rate of absorption of NSAIDs
Do not use with sucralafate