10.2.1 Anti-emetics, Anti-muscarinics and Anti-histamines Flashcards
In the brain what is responsible for vomiting?
Vomiting centre
Where is the vomiting centre found?
Medulla
What are the steps of vomiting?
- Deep breath
- Glottis closes
- Abdominal muscle contraction
- Lower oesophgaeal sphincter relaxes
- Retrograde peristalsis of small bowels
What are parts of the brain, found in the medulla, have involvement with vomiting?
Vomiting centre
- Intergrates incoming signals
- Co-ordinates emesis
Chemoreceptor trigger zone
- Main site for sensing emetic stimuli
Vestibular nuclei (CNVIII)
- Input from the labyrinth
- Balance control
What inputs act on the vomiting centre which are not in the medulla?
Higher cortical centres
- Pain
- Repulsive sights and smells
- Emotional factors
Vagal afferents
- Convey signals from gut to brainstem
Enterochromaffin cells
- Sense toxic chemicals or toxins in gut
What neurotransmitters act on the vomiting centre?
Neurokinin 1 (NK1)
ACh muscarinic
Histamine 1 (H1)
Serotonin (5HT2)
What components of the vestibular nuclei send impulses to the vomiting centre?
Semi-circular canals
Utricle
Saccule
Anything involved in motion
What is responsible for motion sickness and what causes it?
Vestibular nuclei
Caused by:
- Travel
- Sudden fast movements (roller coasters)
What receptors are present in vestibular nuclei?
ACh Muscarinic
H1
Motor Vehicle - Muscarinic Vestibular
Motor-movement- vestibular = movement
Hearing- vestibulocochlear, other function of CNVIII
Hearing- Histamine
What is an example of an anti-muscarinic?
Hyoscine hydrobromide
Works centrally, therefore systemic effects
What are the adverse effects of anti-muscarinics
Competitively blocks ACh receptors therefore anti-SLUDGE
Sedation
Constipation
Dizziness
Dry mouth
Visual issues
Confusion
When should you not give anti-muscarinics?
Elderly patients
Glaucoma
What are some important drug to drug interactions with anti-muscarinics?
Anti-psychotic medications
Why is Hyoscine butylbromide not used for motion sickness?
Does not act centrally
Where do H1 antagonists act?
Vomiting centre
Vestibular nuclei
How do H1 antagonists work?
Inhibits histaminergic signals from vestibular system to CTZ
Fill out the table
What are the adverse effects of H1 antagonists?
Sedation
Anti-SLUDGE:
- Dry mouth
- Constipation
- Urinary retention
- Blurred vision
When should you not give H1 antagonists?
Epilepsy
Glaucoma
Urinary retention
Children
Elderly patients
What anti-histamines are sedative?
Cyclizine pill capsules cause drowsiness
Cyclizine
Promethazine
Chlorphenamine
Cinnarizine
Diphenhydramine (Benadryl)
What anti-histamines are not sedative?
Cetirizine
Fexofenadine
Loratadine
Why are some anti-histamines not sedative?
Second generation anti-histamines are unable to cross the blood brain barrier
Who is affected by motion sickness?
Women > men
Children > adults
People who have migraines
How can motion sickness be prevented?
Hydration
Position in vehicle
Distraction
What drugs are given for motion sickness?
Anti-muscarinics
- Hyoscine hydrobromide
Anti-histamines
- Cinnarizine
- Cyclizine
- Prochlorperazine
