13.1 GI Motility Drugs

Question 1

What can cause vomiting?

Answer 1

Problems with the vestibular system
Drug Induced - Post Op, Chemotherapy
Alcohol
Pregnancy
Unpleasant Stimuli - Smells
Infections - Salmonella
Raised ICP

Question 2

What areas of the brain are involved in vomiting?

Answer 2

The Area Postrema
The Medullary Centres
The Vestibular Areas

Question 3

What Neurotransmitters are involved in vomiting?

Answer 3

ACh
Histamine
Serotonin
Dopamine

Question 4

What are the 4 classes of Drug we use to treat vomiting?

Answer 4

D2 antagonists
ACh (muscarinic) antagonists
5HT antagonists
Histamine antagonists

Question 5

How do D2 antagonists work?
Examples:
When are they used?

Answer 5

Act on the area postrema

Metoclopramide
Post Operations, if GI cause, Chemotherapy, Migraines

Domperidone
It can increase gastric emptying
Use in acute cases e.g for Parkinsons Disease medication

Question 6

ADRs of D2 antagonists?

Answer 6

Dystonia
Galactorrhoea
Gynacomastia (increased prolactin)

Question 7

What are the stages of vomiting?

Answer 7

Stimulation of the Vomiting Centre - Area Postrema
Warning Signs - lightheaded, fast breathing, feel hot/sweaty, pale

Glottis closes, Soft Palate raises, pyloric sphincter contracts

Diaphragm and abdominal muscles contract, Cardia Relaxes

Question 8

What is metoclopramide?

Pharmacokinetics?

Answer 8

D2 antagonist
Oral, IM, IV
Half life of 4 hours

Question 9

What is Domperidone?

Pharmacokinetics?

Answer 9

D2 antagonist
Oral, Rectal
Doesn’t cross BBB
Extensive 1st Pass Metabolism

Question 10

How do 5HT antagonists work?

When used?

Answer 10

They work on the area postrema and periphery
They prevent vagal stimulation
Post Op
Chemotherapy

Question 11

ADRs of 5HT antagonists?

Answer 11

Headaches
Constipation
Flushing

Question 12

Example of a 5HT antagonist

Answer 12

Ondansteron

Question 13

How do Histamine antagonists work?
When used?
Example?

Answer 13

Acute Cases e.g. MI

Cyclozine

Question 14

How do ACh antagonists work?

When used?

Answer 14

Use in travel sickness
Short Half Life
Take 30 mins to take effect

Question 15

ADRs of Histamine Antagonists?

Answer 15

Drowsiness

Long QT

Question 16

ADRs of ACh antagonists?

Answer 16

Can become tolerant
Can cause systemic anti-muscarinic effects
Constipation
Bradycardia

Question 17

What drugs do you use to treat constipation?

Answer 17

Bulk Forming Laxatives
Osmotically Active
Stool Softeners
Stimulants

Question 18

How do you remember the 4 Constipation Drugs?

Answer 18

BOSS

Question 19

Which treatments do you use if stool is found to be hard

Answer 19

Bulk Forming 
Stool Softener (Faecal Softeners)

Question 20

What laxative should you use if there is soft stool?

Answer 20

Stimulants

Question 21

What lifestyle recommendations would you make to someone with constipation?

Answer 21

Fibre
Five a Day
Fluid
Alter Medication
Exercise

Question 22

What conditions can cause constipation?

Answer 22

Pregnancy
Parkinsons
Diabetes
Dehydration

Question 23

Which Drug do you not use if dehydrated?

Answer 23

Bulk Forming Agents - ispagula

Question 24

Bulk Forming Agents - MoA?

Answer 24

Insoluble vegetable fibre, not absorbed, distends the intestine, stretch receptors causing peristalsis
It also draws H20 into the bowel, to distend as well

Question 25

Bulk Forming Agents - When?

Answer 25

In pregnancy - it is safe! | Takes a few days to work and bring bowel function back to normal

Question 26

Bulk Forming Agents - ADRs?

Answer 26

Flatulence

Question 27

Bulk Forming Agents - Example

Answer 27

Ispagula

Question 28

Bulk Forming Agents - Contraindications

Answer 28

Obstruction Dehydration Ulceration

Question 29

Faecal Softeners - MoA and Example

Answer 29

Stay in the bowel, lubricate and soften stool Glycerol Arachnis Oil

Question 30

Faecal Softeners - When use?

Answer 30

``` If cannot tolerate fibre Very Safe Haemorrhoids Adhesions Anal Fissures ```

Question 31

Faecal Softeners - Contraindicated

Answer 31

In Obstruction

Question 32

Faecal Softeners - Why not very good?

Answer 32

Not always effective | Normally suppository

Question 33

Osmotically Active Laxatives - MoA?

Answer 33

Mg or Na Salts draw water into the bowel, distends the bowel causing peristalsis

Question 34

Osmotically Active Laxatives - When use?

Answer 34

Instant relief needed Before Surgery Before Colonoscopy

Question 35

Osmotically Active Laxatives - PK Examples? When use?

Answer 35

Very Potent Fast Acting Lactulose - liver failure Macrogols - helps dehydration

Question 36

Osmotically Active Laxatives - ADRs

Answer 36

Can cause obstruction

Question 37

Stimulant Laxatives - MoA

Answer 37

Irritate the bowel mucosa, stimulates peristalsis and H2O to go into the bowel

Question 38

Stimulant Laxatives - Examples?

Answer 38

Senna | Castor Oil

Question 39

Stimulant Laxatives - When Use?

Answer 39

Overnight - takes 6/8 hours | Rapid Treatment

Question 40

Stimulant Laxatives - Contraindicated

Answer 40

Not Long Term - melanosis coli | Hypokalaemia

Question 41

Stimulant Laxatives - ADRs

Answer 41

Obstruction Cramps Atony Hypokalaemia

Question 42

How do you treat diarrhoea?

Answer 42

``` Drug treatments treat the symptoms not the cause If can: Treat underlying cause Lifestyle Advice - no caffeine Manage fluids and electrolytes ```

Question 43

What drug classes would you treat diarrhoea with?

Answer 43

Anti-motility - opioids Bulk Forming Agents Bile Acid Sequestants Pancreatic Enzymes

Question 44

Anti-Motility Drugs - MoA? | Examples?

Answer 44

Act on Opioid receptors on the bowel to reduce movement | Codeine, Imodium

Question 45

Anti-Motility Drugs - Containdicated

Answer 45

IBD - Causes Toxic Megacolon

Question 46

Anti-Motility Drugs - Positives?

Answer 46

Increase Anal Tone | Reduce Reflex to Defaecate

Question 47

Anti-Motility Drugs - When use?

Answer 47

Chronic Diarrhoea

Question 48

Bulk Forming Agents, why use in diarrhoea?

Answer 48

Creates a more formed stool

Question 49

When do you use Bulk Forming Agents?

Answer 49

IBS Ileostomy Diverticular Disease

Question 50

When would you use a bile acid sequesterant?

Answer 50

In Crohns Disease | If Bile Salt Induced