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Pharma > 10. GI drugs > Flashcards

10. GI drugs Flashcards

1
Q

ach and gastric pathways to produce acid

A

phospholipase c
ip3 and dag
ca release

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2
Q

histamine and proostaglandins pathways

A

g coupled
camp
protein kinase

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2
Q

antacids

A

Antacids are basic compounds that used to neutralize hyperacidity of the gastric contents.

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3
Q

antiacids Broadly classified in to:

A

1) Non-systemic or local, and
2) Systemic antacids.

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4
Q

local define plus example

A

Local/non-systemic antacids : which are non absorbable from GIT & preferable in the treatment of peptic ulcer than the absorbable(systemic) antacids. they include:
Magnesium hydroxide/magnesium trisilicate, aluminum hydroxide

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5
Q

local antiacids differ in

A

Differ in terms of acid neutralizing capacity, onset and duration of action, and adverse effects

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6
Q

Magnesium hydroxide

A

Magnesium hydroxide has very good acid neutralizing capacity, rapid onset and relatively short duration of action

causes diarrhea with prolonged use

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7
Q

Aluminum hydroxide

A

Aluminum hydroxide has relatively low acid neutralizing capacity, slow onset but prolonged duration of action

causes constipation with prolonged use due to aluminum’s smooth muscle relaxant and mucosal astringent action

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8
Q

Aluminum hydroxide binds ………. in the intestine and prevents its absorption

A

phosphate

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9
Q

Rebound acidity is mild and brief upon withdrawal of both

A
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10
Q

Calcium carbonate is a potent and rapidly acting(but not commonly used)
because

A

Liberates carbon dioxide can cause distention and discomfort
Calcium diffuses in to gastric mucosa increase HCl production directly by parietal cells(rebound acidity more marked)

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11
Q

Combinations of magnesium and aluminum salts are preferred b/c:

A

Adverse effects will cancel out( diarrhea and constipation)

Rapid action of magnesium salts combined with long action of aluminum salts maximizes the beneficial effects

Different combination preparations are available

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12
Q

sodium bicarbonate rarely used as gastric antacid b/c:

A

Produces carbon dioxide in stomach → cause distention, discomfort and ulcer perforation

Alters(increases) the pH of blood & other body fluids

Effect is short lasting and rebound acidity

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13
Q

H2 antagonists
define plus type

A

Counteract the hypersecretory effect of the endogenous histamine.
reversible competitive antagonists

Include: cimetidine(prototype), ranitidine, nizatidine, famotidine

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14
Q

All have equal efficacy but differ in terms of

A

potency

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15
Q

Cimetidine

A

inhibits cytochrome P450 and can slow metabolism and, thus, potentiate the action of several drugs ( warfarin, diazepam, phenytoin, quinidine, carbamazepine etc.)

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16
Q

side effects of cimetedine

A

It has antiandrogenic effect that manifest as gynecomastia, loss of libido, impotence, decreased sperm count

displacement of dihydrotestosterone from androgen receptors and increased prolactin release and inhibits degradation of estradiol by the liver

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17
Q

Uses of H2 antagonists

A

Duodenal ulcer
Gastric ulcer
Stress ulcers and gastritis
Zollinger-Ellison syndrome
GERD
However, b/c of higher efficacy of PPIs and equally good tolerability, they are not first-line agents

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18
Q

Proton Pump Inhibitors(PPIs)
dfine plus example

A

Are prodrugs activated in acidic environment of parietal cells’ canaliculi(charged form binds the enzyme)
Can be inactivated in the stomach and the presence of food decreases their bioavailability(given one hour before meal)
Example: Omeprazole(prototype), lansoprazole, pantoprazole, esomeprazole…

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19
Q

Mechanism of Action of ppi

A

Irreversibly bind to H+/K+ ATPase enzyme and inhibit it.

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20
Q

Steady state concentrations cause 80-98% inhibition of acid secretion.(Although their half-lives are 1-2 hours have long lasting effect; once daily administration

A
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21
Q

Duodenal ulcer heals faster than gastric ulcer(healing can be enhanced by 40 mg in both DU and GU)

A
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22
Q

ppi use

A

1) Peptic ulcer(omeprazole 20 mg is equally or more effective than H2 blockers)
Duodenal ulcer heals faster than gastric ulcer(healing can be enhanced by 40 mg in both DU and GU)
Are drugs of choice for NSAIDs-induced peptic ulcers
Can prevent relapse also

2) Bleeding peptic ulcer: acid enhances clot dissolution promoting ulcer bleed
Suppression of gastric acid facilitates clot formation reducing blood loss & rebleed
3) Stress ulcers
4) GERD
5) Zollinger-Ellison syndrome
6) Prophylaxis of aspiration pneumonia

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23
Q

Cytoprotective(ulcer protective) Agents
define plus drugs

A

Enhance mucosal protective mechanisms
Some may reduce acid secretion and exert antibacterial activity as well
Drugs include: sucralfate, colloidal bismuth subcitrate, tripotassium dicitratobismuthate, misoprostol

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24
Q

Sucralfate used for

A

Used for stress ulcers, erosions, PUD

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25
Q

Sucralfate
Attracted to and binds to

A

the base of ulcers and erosions, forming a protective barrier over these areas and protects the areas from acid and pepsin, action entirely local

26
Q

sucralfate also augments gastric mucosal synthesis
of

A

prostagladin

27
Q

sucralfate is Preferred in patients who

A

continue to smoke

28
Q

Antacids should not be taken with sucralfate as its action requires

A

acid pH

29
Q

Misoprostol

A

Synthetic prostaglandin analogue

30
Q

Prostaglandins have cytoprotective activity:

A

Protect gastric mucosa from injury by enhancing local production of mucus or bicarbonate
Acid secretion and gastrin production are inhibited
Helps to maintain mucosal blood flow

31
Q

Major problems in the use of misoprostol are

A

abdominal cramps, diarrhea, uterine bleeding, abortion

32
Q

Colloidal bismuth subcitrate:

A

water soluble but precipitates at pH < 5
It heal 80-90 % of ulcers at 8 weeks

33
Q

Possible mechanisms of action:
of colloid bismuth subcitrate

A

Stimulation of mucosal prostaglandin production
Formation of a coat on the ulcer
Detaches H. pylori from the surface of mucosa and kills it

34
Q

Triple Therapy for H. pylori

A

One PPI plus 2 antibiotics each BID for 2 wks.
Omeprazole(20mg) + Clarithromycin(500mg) + Amoxicillin (1g)

Omeprazole(20mg) + Clarithromycin(500mg) + Metronidazole( 500mg)
Particularly useful in penicillin allergy

35
Q

Antidiarrheal drugs
Principles of management:

A

Treatment of fluid depletion, shock and acidosis
Maintenance of nutrition
Drug therapy

35
Q

anti diarrheal should not be used in patients with

A

bloody diarrhea, high fever, or systemic toxicity because of the risk of worsening the underlying condition.

36
Q

Oral rehydration is possible if glucose is added with salt/glucose coupled sodium transport

A
37
Q

Drug therapy consists of:

A

Specific antimicrobial drugs
Nonspecific antidiarrheal drugs

38
Q

Specific antimicrobials

A

co-trimoxazole, ciprofloxacin, norfloxacin, ampicillin, tetracycline, and erythromycin
Diarrhea due to protozoa(amebiasis and giardiasis) can be treated with metronidazole and diloxanide furoate

39
Q

Nonspecific antidiarrheal agents include:

A

1) Adsorbants
2) Antisecretory drugs
3) Antimotility drugs

40
Q

Adsorbants include
plus moa

A

activated charcoal, kaolin
Coat the walls of the GI tract
Bind to the causative bacteria or toxin, which are then eliminated through the stool

41
Q

Antisecretory drugs include

A

include sulfasalazine, mesalazine, corticosteroids
Reduce water secretion in to intestine
Used for treatment of inflammatory bowel diseases

42
Q

Antimotility drugs include

A

opioids such as loperamide, diphenoxylate and codeine
Decrease propulsive movements and diminish intestinal secretions while enhancing absorption

43
Q

Uses of Laxatives/ purgatives/ cathartics

A

Constipation(main use); other uses include:
Expulsion of parasites after antihelimentic use
Clear alimentary tract before surgery and radiological procedures
For management of poisonings

44
Q

Laxatives should be avoided if there is

A

an intestinal obstruction, severe abdominal pain, symptoms of appendicitis, ulcerative colitis,

45
Q

Classes of Laxatives:

A

Bulk-forming laxatives
Emollient/stool softeners
Osmotic laxatives
Stimulant/ irritant laxatives

46
Q

Bulk-Forming
MOA plus example

A

Highly fiber non-digestible and non-absorbable hydrophilic colloids
Absorb water to increase bulk and swell
Distends bowel to initiate reflex bowel activity
Examples: psyllium, methylcellulose

47
Q

Emollient / Stool softeners

A

Act by softening stool
Lubricate the fecal material and intestinal walls
Examples: Stool softeners: docusate salts
Lubricants: liquid paraffin (10 ml every 8-12 hrs as required)
Glycerin suppository (1 gm rectally at night after moistening with water)

48
Q

Osmotic laxatives

A

Soluble but non-absorbable compounds whose osmotic action draws water in to the intestinal lumen.
Result: bowel distention, increased peristalsis, and evacuation
Examples: magnesium sulfate , Mg(OH)2, magnesium citrate, sodium phosphate, sorbitol, lactulose

49
Q

Use of osmotic laxatives

A

Chronic constipation
Bowel diagnostic and surgical preparations
Removal of helminthes and parasites

50
Q

Stimulant Laxatives

A

Stimulate intestinal enteric nerves system and leads to increase in intestinal motility and fluid secretion
Examples: castor oil, senna, cascara, bisacodyl

51
Q

Use

A

Acute constipation
Diagnostic and surgical bowel preparations

52
Q

Emetics

A

Example: ipecac syrup and apomorphine

53
Q

Emesis should not be induced if the patient has ingested certain

A

volatile hydrocarbons and caustic substances, CNS stimulants

54
Q

anti emetics include

A

Antihistamines
Anticholinergics
Dopamine Antagonists
Phenothiazine Derivatives
5-HT3 receptor antagonists

55
Q

Antihistamines

A

Example: Dimenhydrinate, diphenhydramine, and meclizine hydrochloride
block peripheral stimulation of the emetic center.
Most effective in motion sickness

56
Q

S/E
C/I:

A

S/E: sedation.
C/I: active work such as driving

57
Q

Anticholinergics

A

Example: Atropine, scopolamine (hyoscine)
They block Muscarinic receptors in the GIT and inhibit motility and secretion.

58
Q

Dopamine Antagonists

A

Example: Metoclopramide
Dopamine antagonist that centrally inhibits stimulation of the CTZ
decreasing a peripherally associated stimulation of the emetic center.
S/E: drowsiness, fatigue, dizziness, weakness

59
Q

Phenothiazine Derivatives

A

Example: Promethazine , Chlorpromazine, prochlorperazine
Act at the CTZ by inhibiting dopaminergic transmission.
They also decrease vomiting caused by gastric irritants, suggesting that they inhibit stimulation of peripheral vagal and sympathetic afferents.

60
Q

5-HT3 receptor antagonists

A

ondansetron, granisetron

61
Q

serotonin receptor antagonists use 3

A

chemotherapy induced vomiting, disease-induced vomiting, and
post-operative vomiting

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