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Week 10: Abdominal Pain > Pharm of Drugs in Upper GI Disease > Flashcards

Pharm of Drugs in Upper GI Disease Flashcards

1
Q

How is H+ secreted into the lumen of the stomach?

A

Via a H/K ATPase (H out, K in)

Constitutive activation via histamine release from enterochromaffin-like cells

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2
Q

Prostaglandin E2

A

Mediates mucus and bicarb secretion from mucus cells

Via EP receptors

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3
Q

2 general ways to treat acid-related disorders

A

Neutralize or reduce gastric levels of H+/ H pylori

Strengthen/enhance protective factors

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4
Q

5 options for acid neutralizing/lowering drugs

3 main ones, 2 others

A 
Antacids
Histamine H2 receptor antagonists
Proton pump inhibitors
Antimuscarinics
Gastrin receptor antagonists
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5
Q

Antacids

3 examples and MOA

A

Al(OH)3, Mg(OH)2, CaCO3
Direct neutralization of already secreted stomach acid
Increased gastric pH
No receptor interaction (direct chemical interaction)

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6
Q

Pharmacokinetics of antacids

A

Counter ions (Al, Ca, Mg) are poorly absorbed
They may chelate other drugs, affecting their absorption
Altered pH may affect drug absorption

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7
Q

Indications for antacids

A

Heartburn/mild GERD

Dyspepsia

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8
Q

Side effects from antacids

A

Carbonate based salts: belching (CO2 is produced)
Ca: hypercalcemia
Al: constipation, hypophosphatemia (impaired absorption)
Mg: diarrhea

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9
Q

H2 receptor antagonists

A

Competitive, selective block of histamine H2 receptors
The -tidine drugs (ranitidine)
Reduced (but not eliminated) acid secretion
ACh and gastrin pathways in response to a meal are still active
Most effective in reduction of nocturnal acid secretion

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10
Q

Pharmacokinetics in H2 receptor antagonists

A

Oral, intramuscular, and intravenous formulations
Bioavailability is 50%, need a twice daily administration (except nizatidine - oral, minimal 1st pass metabolism)
Renal elimination

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11
Q

Indications for H2 receptor antagonists

A

GERD
Peptic ulcer disease
Dyspepsia
Prevention of bleeding from stress-related gastritis

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12
Q

Some common and some rare side effects from H2 receptor antagonists

A

Common: diarrhea (or constipation), headache, drowsiness/fatigue, muscle pain
Rare: confusion/agitation, delirum/hallucinations, slurred speech

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13
Q

Proton pump inhibitors

A

The -prazole drugs (ex: omeprazole)
Irreversible inactivation of proton pump common to ALL triggers of gastric acid secretion (inhibits the H/K ATPase)
Restoration of function requires new proton pump synthesis (takes 18-24 hours)
Relatively selective for parietal cell proton pumps

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14
Q

Pharmacokinetics of PPIs

A

Parietal cell access requires systemic absorption (oral formulations require enteric coating)
Prodrug molecules activated by acid (best if taken within 30-60 mins of meal)
Drug interactions: altered pH (reduced absorption of some drugs), competition for certain cytochrom P450 enzymes

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15
Q

Indications for a PPI

A

Gastric/duodenal ulcer (H pylori associated or NSAID induced)
GERD
Prevention of bleeding from stress-related gastritis
Gastric hypersecretory conditions

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16
Q

Common side effects of PPIs

A 
Generally well-tolerated
Nausea
Diarrhea (or constipation)
Abdominal pain
Flatulence
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17
Q

Antimuscarinics

A

Work on food induced pathways
Ex: pirenzipine
Utile and effective, but side effects!

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18
Q

Gastrin receptor antagonists

A

Ex: proglumide
Work on food induced pathways
Pathway inhibited at pH < 2.5 (won’t give you tangible benefits)
Blocks the CCK2/B receptor

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19
Q

Treatment for H pylori

A

PPI and two antibiotics and 14 days (triple therapy)
Clarithromycin and amoxicillin or metronsazole
Or PPI alone for 6 weeks

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20
Q

Misoprostol

A

Prostaglandin E1 analogue (emulates endogenous PGE2)

Direct effects on parietal cells (inhibitory) or mucus cells (stimulatory)

21
Q

Pharmacokinetics of misoprostol

A

Short half-life
Frequent dosing
No impact on cytochrome P450

22
Q

Indication for misoprostol

A

NSAID-induced ulcers

23
Q

Contraindication of misoprostol

A

Pregnancy

Its a strong uterine stimulant so there is a huge uterine stimulant

24
Q

Side effects from misoprostol

A

Diarrhea
Abdominal cramping
Uterine contraction
All because prostaglandin E1/E2 to stimulate GI/uterine smooth muscle

25
Q

Sucralfate

A 
Al(OH)3-sucrose sulfate complex
Acid release anionic sulfated sucrose
Binds to charged proteins in ulcer
Viscous, sticky, protective barrier
Indirect stimulation of PGE2 production
26
Q

Pharmacokinetics of sucralfate

A

Localized action, minimal systemic absorption
Short effect (6 hours)
Take on empty stomach

27
Q

Indications for sucralfate

A

Gastric and duodenal ulcer

28
Q

Side effects of sucralfate

A

Al-induced constipation

May reduce absorption of some other drugs (Direct binding, or impaired membrane crossing)

29
Q

Bismuth subsalicylate

A

Coat ulcers to form a physical protective barrier
Increased PGE2, HCO3 and mucus production
Antimicrobial against H pylori
Reduces stool frequency

30
Q

Pharmacokinetics of bismuth subsalicylate

A

Dissociated in stomach, acts locally

Only salicylate substantially absorbed

31
Q

Indications for bismuth subsalicylate

A

Adjuvant to triple therapy for H pylori-induced ulcers

Acute diarrhea

32
Q

Contraindications of bismuth subsalicylate

A

Children with viral infections (Reye’s syndrome)

Allergies to ASA

33
Q

Side effects as bismuth subsalicylate

A

Black stool (reaction with hydrogen sulfide in colon, may be confused with GI bleeding)
Blackening of tongue
Constipation

34
Q

Prokinetic drugs

A

Ex: metoclopramide and domperidone
Both dopamine D2 receptor antagonists
Metoclopromaide has additional activity as agonist of serotonin receptors
Relieve basal dopamine inhibition of upper GI tract, stimulating peristalsis and facilitating gastric emptying
Move things along the tract faster (less material in the GI tract that can splash up into the esophagus)

35
Q

Pharmacokinetics of prokinetics drugs

A

Metoclopromide is available in oral and parenteral formulations
Domperiodone has greater first-pass metabolism
Short duration of action
Hepatic metabolism

36
Q

Indications of prokinetic drugs

A

GERD
Impaired gastric emptying
Nausea and vomiting
Postpartum lactation stimulation

37
Q

Contraindications of prokinetic drugs

A

Situations where GI motility is harmful

38
Q

Side effects of prokinetic drugs

A

GI crampings
Diarrhea
Hyperprolactinemia
Metoclopromide (not domperidone) crosses BBB

39
Q

Anti-emetic pharmacology

A

Based on receptor expression in brainstem vomiting center and/or chemoreceptor trigger zone
Ex: Ondansetron, Dimenhydrinate, Scopolamine

40
Q

Ondansetron

A

Antagonist of serotonin 5-HT3 receptors

Vomiting center, chemoreceptor trigger zone, vagal afferents

41
Q

Indications for ondansetron

A

Chemotherapy-induced nausea and vomiting

Postoperative and postradiation nausea and vomiting

42
Q

Side effects for Ondansetron

A

Headache
Dizziness
Constipation

43
Q

Dimenhydrinate

A

Antagonist of histamine H1 receptors (some anticholinergic activity)
Relatively weak anti-emetic activity (can be used as adjuvant)

44
Q

Indications for dimenhydrinate

A

Motion sickness (prevention or treatment)

45
Q

Side effects of dimenhydrinate

A

Dizziness
Sedation/drowsiness
Dry mouth
Urinary retention

46
Q

Scopolamine

A

Antagonist of muscarinic receptors
Comparable efficacy to dimenhydrinate
Best administered as transdermal patch

47
Q

Indication for scopolamine

A

Motion sickness (prevention and treatments)

48
Q

Side effects of scopolamine

A

Antagonist of muscarinic receptors when given orally
Comparable efficacy to dimenhydrinate
Best administered as transdermal patch

Week 10: Abdominal Pain (9 decks)

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