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Pharm Exam 6 > L 27-28 GI > Flashcards

L 27-28 GI Flashcards

1
Q

Name some antacids and their common side effects

A

Sodium bicarbonate: produces CO2 which can be harmful, metabolic alkalosis, sodium dangerous in CHF Calcium carbonate: alkalosis, milk alkali from too much Ca, acid rebound Magnesium hydroxide: poorly absorbed, diarrhea, Mg++ may accumulate if kidney function low Aluminum hydroxide: constipation, combined with Mg, low renal function may cause problems

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2
Q

What are the benefits and downsides to antacids?

A

Antacids are useful for immediate relief of heartburn and gastritis. However, it is a temporary fix and can result in a rebound effect. Must be careful with high Na levels. They also have an effect on drug absorption by changing the pH of the stomach.

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3
Q

Describe the production of acid in the stomach including signaling molecules, receptors, and pathways

A
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4
Q

Describe the mechanism of action for H2 antagonists as well as general characteristics of these drugs

A

H2 signals parietal cells to produce H+ by increasing cAMP through Gs coupled receptor.

This increases the presence of kinases that activate the H+/K+ ATPase

Blocking this receptor blocks a signal to produce H+

These are best at reducing nocturnal acid production

Few side-effects: headache, dizziness, rash, itch, nausea

Cimetidine is unique in that it is anti-testosterone causing gynecomastia, loss of libido, and impotence. It also inhibits P-450 system causing numerous drug interactions.

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5
Q

Describe the four cells involved in acid production in the stomach and the signaling molecules used between them

A
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6
Q

Name the H2 blockers

A

Cimetidine

Ranitidine

Famotidine

Nizatidine

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7
Q

What drig interactions are possible with Cimetidine?

A

Cimetidine affects the P-450 system and therefore has an effect on many drugs.

Effect most commmonly on drugs with narrow therapeutic window such as: warfarin, phenytoin, theophylline, propranolol, benzos, tca, nifedipine, digoxin, quinidine

Other H2 blockers do not inhibit metabolism!

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8
Q

Mechanism of action for PPI’s

A

Bind irreversibly to H+/K+ ATPase completely blocking production of H+

Irreversible binding allows a longer duration of action and fewer doses needed

Prodrug that must be activated and therefore is taken 30 min before meals

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9
Q

Name the PPI’s

A

Omeprazole

Esomeprazole

Lansoprazole

Rabeprazole

Pantoprazole

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10
Q

Side effects of PPI’s

A

N/D, colic weight gain

Osteoporosis from decreased Ca++ absorption

Hypomagnesia causing muscle spasms

Increased risk of pneumonia from bacterial overgrowth

Possible that Omeprazole inhibits P-450

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11
Q

Sucralfate (Carafate)

A

Provides a protective barrier for the stomach

Causes constipation

Rarely used

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12
Q

Misoprostol (cytotec)

A

Prostaglandin E1 analogue

Prevent damage from NSAID use

Causes diarrhea like all PG’s

Must not be used in pregnancy

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13
Q

Metoclopramide

A

D2 antagonist increasing Ach release which increases parasympathetic tone to increase motion of the bowels

Also acts as anti-emetic

Cramping and diarrhea common

High doses cause parkinson-like symptoms

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14
Q

Bethanechol

A

Prokinetic agent

Muscarinic agonist

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15
Q

Erythromycin

A

Acts on motilin receptors as a prokinetic agent

Sometimes used for diabetic gastroparesis

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16
Q

Glycopyrroate, dicyclomine, TCA’s

A

Muscarinic antagonists used to treat IBS

TCA’s good for chronic pain

17
Q

Alosetron (Lotronex)

A

5HT3 receptor antagonist

used to treat IBS with severe diarrhea in women

Constipation most common side effect

GI perforation and obstruction possible

18
Q

Tegaserod (Zelnorm)

A

5HT4 partial agonist–stimulates peristalsis

For IBS with constipation in women

Diarrhea most common side effect

Caution with gall-bladder problems

Taken off market in 2007

19
Q

Anti-emetic agents

A

Ondansetron (Zofran), Granisetron (Kytril), Dolasetron (Anzemet), Palonosetron (Aloxi)

5HT3 antagonists used to prevent nausea and vomiting

Few side effects

20
Q

Prochlorperazine

Promethazine

A

Block DA, muscarinic, histamine receptors

Anti nausea/emetic

Post-op, gastroenteritis, chemo

Highly sedating–don’t use with alcohol

21
Q

What is one of the best stimulants of peristalsis?

A

Stretching of the walls of the intestines

22
Q

How is bowel motility related to fluid absorption and secretion?

A

Decreased motility allows more timef or absorption and therefore the stool becomes more dense leading to constipation

23
Q

What are the different types of laxatives?

A

Bulk forming: mild

Osmotic: intense, cathartic

Mucosal agents: irritant

Lubricating

Stool softening

24
Q

Fiber as a laxative

A

Bulk forming laxative

Must be taken with lots of water otherwise will draw water from the body

Bloating and flatulance are common

Some may absorb drugs

25
Q

What are the osmotic laxatives?

A

Magnesium hydroxide–also stimulates the GI tract

Sodium salts–caution with the sodium in CHF patients

Sorbitol, mannitol, sucralose

26
Q

Lactulose

A

Laxative, but also used in cirrhosis and liver disease to decrease ammonia levels by converting to lactic acid in the gut and decreasing pH so the ammonia is ionized and won’t get absorbed.

27
Q

Polyethylene glycol

A

Laxative

Insoluble, holds water in intestine

Used as prep for colonoscopy

Miralax OTC for occasional constipation

28
Q

Mucosal agents for treatment of constipation

A

Mucosal agents cause peristalsis by irritating the bowel

They also enhance secretion and inhibit absorption of H2O

Mild action: Bisacodyl, Senna

Intense: Castor oil–requires bile, stimulates the uterus so must be avoided with pregnancy

29
Q

What are the lubricants and softeners for treating constipation?

A

These increase the bulk as well as lubricate and soften

Mineral oil, Docusate, Glycerin

All considered to be not very effective

30
Q

Lubiprostone (Amitiza)

A

PG E1 analogue (remember that all PG’s cause major diarrhea)

Activates Cl- channels in luminal cells to increase fluid secretion

No effect on elextrolytes, no dependence, nausea most common side effect

31
Q

Alvimopan (Entereg)

A

Opioid mu-receptor antagonist

Only has peripheral effects (no central)

Selective for GI tract

Used post-op for constipation from opioids

Don’t use if opioids used for >7 days pre-op–causes increased MI

Only used in the short term and in the hospital

Methylnaltrexone is similar

32
Q

What are some common causes for diarrhea?

A

Pathogens, IBS, inflammation, malabsorption, laxatives, thyroid disease (hyperthyroid), drugs

33
Q

Opioids used in diarrhea treatment

A

Loperamide (Imodium): does not enter CNS, low abuse potential

Diphenoxylate/atropine (Lomotil): opiod with atropine, reduces abuse potential, increases effectiveness with anticholinergic effects

34
Q

What are some contraindications to using opioids for diarrhea treatment?

A

Infections: decreases expulsion of pathogens

Ulcerative colitis: causes toxic megacolon

Recovering drug addicts

35
Q

Bismuth salicylate

A

Treatment for diarrhea

Absorbs water and pathogens

Used for traveller’s diarrhea

Salicylate is anti-inflammatory

Causes black tongue, mouth, stool

Contraindicated in patients allergic to aspirin, kids, asthmatics

36
Q

Octreotide

A

Somatostatin analogue

Treats diarrhea caused by GI tumors

Decreases release of 5-HT, gastrin, CCK

Decreases GI motility

Cyproheptidine is a 5-HT antagonist also used for carcinoid

37
Q

Simethicone

A

Coats gas and dissipates it decreasing bloating and flatulence

38
Q

Sulfsalazine

A

Used in IBD

anti-inflammatory 5-aminosalicylic acid plus sulfapyridine

Gut bacteris activate it

Allergic response possible to salicylates

Avoid in kids–Reye’s syndrome

Pharm Exam 6 (10 decks)

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