Pharmacological basis of therapy

Question 1

Antagonist affinity

Answer 1

Measure of how well a drug binds to a receptor

Question 2

Prostaglandin analogue

Answer 2

Misoprostol - agonist at PG receptors
Suppress acid release + promote cytoprotection
Cause uterine contractions

Question 3

Prokinetic drugs

Answer 3

Cause gastric emptying - movement of gastric contents from stomach to duodenum (help GORD)

Question 4

Example of prokinetic drugs

Answer 4

DOMPERIDONE

METOCLOPRAMIDE

Question 5

What can metoclopramide be combined with?

Answer 5

Analgesics - to accelerate absorption

Question 6

How do we eradicate H.pylori?

Answer 6

Triple therapy

Question 7

What is triple therapy?

Answer 7

Combination therapy

Question 8

What does triple therapy consist of?

Answer 8

2 antibiotics + PPI and/or H2RA

Question 9

How long to take triple therapy?

Answer 9

1 week then PPI alone

Question 10

Example of PPI

Answer 10

Omeprazole
Pantoprazole
Lansoprazole

Question 11

What PPIs are OTC

Answer 11

Omeprazole + pantoprazole

Question 12

Adverse effects of PPIs

Answer 12

Inhibit H+ secretion by more than 90% - leading to achlorydria
Increase risk of Campylobacter infection (food poisoning)

Question 13

Adverse effects of PPIs

Answer 13

Inhibit H+ secretion by more than 90% - leading to achlorydria
Increase risk of Campylobacter infection (food poisoning)

Question 14

What activates PPIs

Answer 14

Acidic pH

• enters body
• passes to parietal cells
• pka means activated at low pH
• localises action

Question 15

What is rebound acid hypersecretion

Answer 15

Follows after cessation of H2RAs + PPIs
Increases acid release
Increase dyspepsia symptoms
Avoid prolonged usage

Question 16

How do you treat/manage rebound acid hypersecretion?

Answer 16

Antacids

Question 17

Affinity constant

Answer 17

Ka

Question 18

Dissociation constant

Answer 18

1/Ka = Kd

Question 19

Kd

Answer 19

Concentration at which the drug occupies half of the receptor population

Question 20

A high affinity drug has…

Answer 20

A low Kd (low molarity drug)

Question 21

Examples of H2RA

Answer 21

Cimetidine
Ranitidine
Nizatidine
Famotidine

Question 22

H2RA

Answer 22

Coupled with adenylyl cyclase to increase cAMP

which activates the proton pump

Question 23

Alginates

Answer 23

Combine with saliva to form viscous foam

Floats on gastric content forming a raft which protect oesophagus from reflux

Question 24

Examples of antacids

Answer 24

Sodium bicarbonate
Magnesium hydroxide
Aluminium hydroxide

Question 25

Domperidone

Answer 25

Increased closure of oesophageal sphincter (good for reflux) + opens lower sphincter

Question 26

Metoclopramide

Answer 26

Acts locally to increase gastric motility + emptying

Question 27

What are the antibiotic that can be used for triple therapy

Answer 27

Amoxicillin
Clarithromycin
Metronidazole

Question 28

Calculate pA2

Answer 28

-logKd

Question 29

Use of H2RAs

Answer 29

Reduce gastric acid secretion

• provide symptomatic relief
• promote ulcer healing
• reduce need of surgeru in ulceration

Question 30

When are H2RAs best given

Answer 30

At night

Question 31

Why does H2RAs have a lot of drug interactions

Answer 31

Inhibit cytochrome P450 + metabolism of drugs = drug interactions

Question 32

What drugs metabolism are affected by H2RAs

Answer 32

Oral anticoagulants
Phenytoin
Carbamazepine
Tricyclic anti-depressants

Question 33

What H2RA does not interact with other drugs

Answer 33

Ranitidine

Question 34

Misoprostol

Answer 34

Agonist at PG receptor

Suppress acid secretion + promote cytoprotection

Question 35

What do misoprostol cause

Answer 35

Uterine contractions

Question 36

What are uterine contractions contra-indicated with

Answer 36

Females of child-bearing age

Question 37

How do we accelerate absorption of metoclopramide

Answer 37

Combining it with analgesics