B5 The pharmacological basis of therapy Flashcards

1
Q

Do antacids provide a cure?

A

no but they provide relief

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2
Q

Give examples of antacids

A

sodium bicarbonate
magnesium hydroxide
aluminium hydroxide

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3
Q

How to alginates work?

A

alginic acid combine with saliva and forms a viscous foam, this floats on the gastric contents forming a raft which protects the oesophagus during reflux

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4
Q

Why not use atropine?

A

suppresses acid production but has antimuscarinic side effects

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5
Q

What are examples of H2 receptor antagonists?

A

cimetidine
ranitidine
famotidine

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6
Q

Are H2 receptor antagonist drugs for long term or short term use and what class are the low and high doses?

A

short term
low-OTC
high-POM

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7
Q

What does maximum response equal?

A

efficacy of drug

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8
Q

What does EC50 equal?

A

concentration of agonist giving 50% of maximal response- potency

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9
Q

What are on the x & y axis of a competitive receptor antagonism graph?

A

x- log conc of agonist

y- pharmacological response

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10
Q

How to antagonists work?

A

they bind at the same site as the agonist & so reduce action of agonist by competition

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11
Q

How can completion from an antagonist be overcome?

A

increase conc of agonist

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12
Q

What is antagonist affinity a measure of?

A

how well the drug binds to a receptor

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13
Q

What is the affinity constant Ka measured in?

A

molar^-1

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14
Q

What is Kd or 1/Ka?

A

dissociation constant, is the conc at which the drug occupies half the receptor population

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15
Q

Will a high affinity drug have a high or low Kd?

A

low

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16
Q

What does pA2=?

17
Q

What does high PA2 mean for affinity?

A

high affinity

18
Q

What are the benefits of H2RAs?

A

reduce gastric acid secretion

provide symptomatic relief

19
Q

What are H1 receptor antagonists?

A

antihistamines

20
Q

Why is cimetidine not chosen over ranitidine?

A

cimetidine inhibits cytochrome P450 & therefore the metabolism of other drugs, whereas ranitidine does not interact this way

21
Q

What drugs does cimetidine interact with?

A

oral anticoagulants
phenytoin
carbamazepine
tricyclic antidepressants

22
Q

What are examples of PPIs?

A

omeprazole, pantoprazole, lansoprazole

23
Q

How to PPIs work?

A

activated by acidic pH, enter body, passes to parietal cells, pKa means activated at lower pH, localised action

24
Q

What are possible ADRs of PPIs?

A

inhibit H+ secretion by > 90%, leads to achlorhydria (absence of HCl)
increase risk of campylobacter infection (food poisoning)

25
What is rebound acid hyper secretion?
following the cessation of H2RAs or PPIs, increase in acid release, increase in dyspepsia symptoms
26
How can you mange rebound acid hyper secretion?
with antacids
27
Give an example of a prostaglandin analogue?
misoprostol
28
How do prostaglandin analogues work?
agonist at PG receptor, suppress acid release and promote cytoprotection
29
What can prostaglandin analogues cause?
uterine contraction, cause miscarriage, abortion
30
How to pro kinetic drugs work?
cause gastric emptying, movement of gastric contents from stomach to duodenum
31
What are two examples of pro kinetic drugs and how do they work?
domperidone- increased closure of oesophageal sphincter and one lower sphincter metoclopramide- act locally to increase gastric motility and emptying
32
What is the most effective treatment for long term cure of ulcers?
H.pylori eradication
33
What is TRIPLE THERAPY and how does it work?
involves an antibiotic, 2 from either; clarithromycin, amoxicillin, metronidazole plus PPI and/ or H2 antagonist triple therapy lasts for one week then PPI alone