Gastrointestinal Pharmacology - Motility Flashcards
(58 cards)
Learning Outcomes:
• List the common therapeutic drug classes used to alter bowel motility (increase and decrease) including opioids, and the names of specific drugs within each class.
• State the mechanism of action of the commonly used therapeutic classes for altering bowel motility.
• Recognise common clinical situations where altering bowel motility is required.
Understood.
Define pro-kinetic
A pro-kinetic agent is a type of drug which enhances gastrointestinal motility by increasing the frequency or strength of contractions, but without disrupting their rhythm.
Define anti-emetic.
A drug that prevents vomiting.
Define anti-spasmodic.
A drug used to relieve spasm of involuntary muscle.
Opioids
Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for acute pain relief, including anesthesia.
What are the main anti-emetics used?
Ondansetron Cyclizine Buscopan Mebeverine Metoclopramide Domperidone
What are the main prokinetics used?
Metoclopramide Cyclizine Domperidone Prucalopride Linaclotide
Explain the area of the brain involved in control of vomiting and the receptors involved.
Medulla oblongata
- receptors involved: Histamine, serotonin (5-HT3), muscarinic and dopamine receptors.
Ondansetron
Use:
Side effects:
Class:
Ondansetron
Use: Ondansetron is prescribed to prevent nausea and vomiting in response to cancer treatment and following surgery.
Side effects: Constipation, feeling hot, headaches. Arrhythmia’s.
Class: Anti-emetic serotonin antagonist.
What is the action of ondansetron?
Highly selective 5 HT3 (serotonin) receptor antagonist.
Metoclopramide
Use:
Side effects:
Class:
Metoclopramide
Use: Used for nausea and vomiting in palliative care.
Side effects: Asthenia; depression; diarrhoea; drowsiness; hypotension; menstrual cycle irregularities; movement disorders; parkinsonism.
Class: Dopamine Antagonist Anti-emetic.
How does metoclopramide work?
Blocks the dopamine mediated relaxation effect on
gastrointestinal smooth muscle.
– Increased response of the gastrointestinal smooth muscle to cholinergic stimulation.
– Increases rate of gastric emptying.
– May also strengthen the lower oesophagus sphincter,
thereby preventing acid reflux.
– Antagonizes D2 dopamine receptors in chemoreceptive.
trigger zone (CTZ) of the medulla, thereby preventing
nausea and vomiting.
Why are you advised to not use dopamine antagonistic drugs for the long term?
They can cause permanent dyskinesia.
Domperidone
Use:
Side effects:
Class:
Domperidone
Use: Anti-emetic - commonly prescribed in IBS - improves symptoms of nausea, vomiting, bloating, and feeling of fullness.
Side effects: Dry mouth, galactorrhoea, gynecomastia, menstrual irregularities, cardiac arrhythmia’s.
Class: D2 Dopamine receptor antagonist - anti-emetic.
How does domperidone work?
Antiemetic properties are related to its dopamine
receptor blocking activity at both the chemoreceptor trigger zone and at the gastric level.
What are the contra-indications where you would avoid using domperidone?
Cardiac disease
GI obstruction
Cyclizine
Use:
Side effects:
Class:
Cyclizine
Use: Travel sickness, nausea, dyspepsia, vomiting, vertigo.
Side effects: Depression, drowsiness, tachycardia, hypotension, constipation.
Class: Histamine 5HT1 Antagonist + Anti-muscarinic.
How does cyclizine work?
Cyclizine works by blocking histamine and muscarinic receptors in the vomiting centre, which prevents the vomiting centre from receiving nerve messages from the vestibular apparatus. This prevents disturbances in the middle ear from activating the vomiting centre and causing nausea, vertigo and vomiting.
What are the contraindications where you would avoid prescribing this drug?
– Cardiac disease – Liver disease – Acute angle glaucoma – GI obstruction – Myasthenia gravis – Active colitis – Urinary retention
Buscopan
Use:
Side effects:
Class:
Buscopan
Use: It relieves the pain of stomach and bowel cramps by helping your digestive system to relax.
Side effects: Tachycardia, Hypotension, Anaphylaxis.
Class: Anti-spasmodic. Anti-muscarinic (anti-cholinergic).
How does buscopan work?
• Peripherally acting anticholinergic agent
• Binds to muscarinic M3 receptors located on
postganglionic parasympathetic nerve endings
on smooth muscle cells.
• Blocks the activity of acetylcholine
• Inhibits smooth muscle contraction
• Antispasmodic effect in the gastrointestinal,
urinary, uterine, and biliary tracts
What are the contra-indications where buscopan should not be used?
– Cardiac disease. – Acute angle glaucoma – GI obstruction – Myasthenia gravis – Active colitis – Urinary retention
What are the four different classes of laxative?
Bulk forming
Osmotic
Stimulating
Softeners
Linaclotide
Use:
Side effects:
Class:
Linaclotide
Use: For relieving symptoms of irritable bowel syndrome (IBS) with constipation and for treating chronic constipation of unknown cause (idiopathic constipation).
Side effects: Diarrhoea; dizziness; gastrointestinal discomfort; gastrointestinal disorders.
Class: Secretagogue and analgesic with laxative activity.
