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Primary Pharmacology > GI Pharmacology > Flashcards

GI Pharmacology Flashcards

1
Q

What gastric ph is desired prior to anaesthetic

A

3.5

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2
Q

Examples of H2 receptor antagonists
How do they work

A

Cimetidine, ranitidine
Reversible competative inhibitor at H2 receptor which usually stimulates acid secretion
Mimic the imidazole ring end of histamine to bond. Inhibits both basal level and stimulated release of acid.

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3
Q

Where are h2 receptors present
Effect of antagonists at these locations

A

Uterus, heart, blood vessels, los
Very little

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4
Q

Side effects of cimetidine

A

Gynaecomastia and impotence (antiandrogen effects)
Cyp450 inhibition
Reduces hepatic blood flow
Inhibition of suppressor T cells worsening autoimmune conditions
Bradyarrhythmias

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5
Q

Time to peak effect of cimetidine

A

80mins

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6
Q

Time to peak effect of ranitidine
Pharmacokinetics of oral administration

A

100mins
T1/2 2.5hrs
Substantial first pass metabolism
Metabolised in liver and causes some inhibition of cyp450

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7
Q

How do proton pump inhibitors work?

A

Effect acid secreting pumps of gastric parietal cells

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8
Q

Structure and pharmacokinetics of ppi

A

Imidazole and benzene ring together
Weak base with a high PKA
Administered in buffered capsules and slowly released
Absorbed whilst non ionised then activated by protination on luminal side (prodrug)
Accumulates and binds strongly to hkatpase pumps preventing h passage

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9
Q

What is the active form of omeprazole

A

Sulphenamide

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10
Q

What is the half life of omeprazole
Why does it last longer

A

3 minutes in plasma
Accumulates around receptors and binds strongly

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11
Q

How is omeprazole metabolised

A

Hepatically

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12
Q

Adverse effects of omeprazole

A

Hypergastrinaemia
Cyp450 inhibition

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13
Q

Effect of prostaglandins on stomach acid secretion
Example

A

Eg misoprostol
Reduce stomach acid secretion and stimulate mucus production thus useful in nsaid induced ulceration

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14
Q

Examples of antacids used in gastric acidic control
Mechanism

A

Aluminium hydroxide, sodium citrate

Simple chemical reaction of acid +base to salt + water

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15
Q

Side effects of antacid use

A

Co2 production with beltching and gastric distension
Very alkaline thus aspiration of the antacid could also cause damage
Alkalosis
salt and water retention (as a lot has to be given for significant effect)

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16
Q

Which antacid is non-particulate
Consequence?

A

Sodium citrate
Less lung damage if aspirated

17
Q

Examples of antispasmodics
Class of drug

A

Anticholinergic
Atropine, hyoscine

18
Q

Effects of anticholinergics on gi tract

A

Reduce acid secretion (higher dose, side effects prohibitory for primary use)
Reduce gi tone (antispasmodic) (lower dose, side effects can be managed usually)
Reduce los tone

19
Q

What improves side effect profile of antispasmodic anticholinergics

A

Not crossing bbb
Specificity for m1 receptor

20
Q

Other than anticholinergics what other drugs can be used as antispasmodics, how do they work

A

Meberverine, Peppermint oil
Direct relaxation of smooth muscle

21
Q

Examples of prokinetic agents
How do they work

A

Domperidone, erythromycin, metoclopramide
Domperidone and metoclopramide acts on D2 receptors peripherally
Erythromycin is a motility receptor agonist
Final common pathway via acetylcholine

22
Q

Catagories mechanism and examples of laxatives

A

Bulking agents - increase stool bulk and retention of water, eg isphaghula husk
Faecal softeners - oily compounds that soften stool, eg liquid parrifin
Osmotic laxatives - draw water into large bowel, eg magnesium salts, lactulose, phosphates
Stimulants - stimulate bowel movement and permeability, eg senna, bisacodyl

23
Q

Risks of stimulant laxatives

A

Hepatotoxicity

24
Q

Which group of laxatives are used in bowel prep

A

Osmotic

25
Q

Issue with faecal softeners

A

Decreased absorption of fat soluble vitamins

26
Q

Protein binding of lansoprazole and omeprazole

A

97 and 95% respectively

27
Q

Bioavailability of lansoprazole and omeprazole

A

85 vs 35%

28
Q

Side effects of lansoprazole and omeprazole

A

rash, puritis, eosinophilia, gynaecomastia, liver dysfunction, low na and Mg

Primary Pharmacology (18 decks)

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