GI pharmacology

Question 1

Name 3 Histamine-2 (H2) receptor antagonists.

Answer 1

1) Cimetidine (Tagamet)
2) Ranitidine (Zantac)
3) Famotidine (Pepcid)

Question 2

What is the MOA of H2 receptor antagonists?

Answer 2

antagonism of gastric H2 receptors inhibits hydrochloric acid production and raises gastric pH

Question 3

What are the drug interaction concerns with Cimetidine (Tagamet)?

Answer 3

inhibits CYP450 enzymes found on hepatic microsomes, thereby interfering with its normal function of metabolizing drugs
-prolongs action of drugs that are metabolized by the liver–> theophylline, coumadin, warfarin, aminophylline, phenytoin, halothane, lidocaine, phenobarbital, diazepam, propanolol, labetalol, meperidine, quinidine, TCAs (imipramine and desipramine), and calcium channel blockers

Question 4

What is special about ranitidine in comparison to cimetidine in regards to side effects?

Answer 4

does not traverse the BBB effectively, so it causes less somnolence, lethargy, confusion, hallucinations, and seizures than cimetidine

Question 5

Why are non-particulate antacids preferred over particulate antacids?

Answer 5

b\c they cause less problems than particulate antacids if aspirated

Question 6

What drug helps to control gastric motility?

Answer 6

metoclopramide (reglan)

Question 7

What are the actions of metoclopramide (Reglan)?

Answer 7

• increase LES tone (prevents reflux into the esophagus)
• increase gastric motility (promotes gastric emptying)
• decrease in tone of pyloric sphincter (permits passage of foodstuffs from the stomach to the small intestine)
• relaxation of the duodenum (this makes room for food coming from the stomach)

Question 8

How does metoclopramide effects gastric pH?

Answer 8

it has No effect on gastric pH

Question 9

Incidence and severity of aspiration pneumonitis are reduced if:
gastric pH is > ______.
gastric volume is < ______.

Answer 9

pH above 2.5

volume < 25mL (0.4ml/kg)

Question 10

Histamine-2 antagonists reduce ________ ________ ______ secretion, and this action increases gastric pH and decreases gastric volume.

Answer 10

gastric hydrochloric acid

Question 11

________ decreases gastric volume without altering pH.

Answer 11

Metoclopramide (reglan)

Question 12

What 3 drugs are competitive dopamine antagonists?

Answer 12

1) droperidol (Inapsine)
2) prochlorperazine (Compazine)
3) metoclopramide (Reglan)

Question 13

Why should droperidol be avoided in the Parkinsons patient?

Answer 13

b\c of its dopamine receptor antagonist activity

Question 14

Which antimuscarinic is used as an antiemetic?

Answer 14

scopolamine

Question 15

Name a selective serotonin-3 antagonist.

Answer 15

ondansetron (Zofran)–> 5HT3 antagonist

Question 16

What is the most common side effect of zofran?

Answer 16

headache