Lecture 18 - Nausea/vomiting Constiption And Diarrhoea Flashcards
What is vomiting/emesis?
Invlountary, forceful expulsion of gastric contents through the mouth
Where is the vomiting centre located in the brain?
Medulla
What is the very general process of vomiting?
Deep breath
Glottis closes
Abdo muscles contract (inc Intra abdominal pressure)
Lower oesophageal sphincter relaxes
Retrograde peristalsis of small bowels
What is regurgitation?
Often seen in babies
When some feed gets brought back up
Not the same as vomiting
What are the receptors that are found in the vomiting centres in the medulla?
Muscarinic ACh
H1(Histamine receptor)
5HT2 (type of serotonin receptor)
NK1 (Neurokinin 1)
What are some stimuli from the cortical centres that may activate the vomiting centre in the medulla?
Pain
Visual stimuli
Smells
Stress
How do we manage vomiting or nausea?
Conservative management (avoid stimuli)
What part of the brain is stimulated when motion sickness occurs?
Vestibular nuclei receive input from labyrinth
What receptors are located in the vestibular nuclei that when are activate lead to motion sickness?
Muscarinic ACh
Histamine 1 receptors
What type of drugs are given to treat motion sickness?
Muscuranic receptor antagonists (competitive blockers)
H1 antagonists
What are some examples of anti Muscarinic drugs that can be used to treat motion sickness?
Hyoscine hydrobromide (works centrally)
What are the adverse reactions of Muscarinic antagonists like hyoscine hydrobromide? (Given for motion sickness)
Sedation
Constipation
Dizziness
Dry mouth
Visual problems
Confusion
What are the contraindications for giving Muscarinic antagonists like hyoscine hydrobromide? (Given for motion sickness)
Elderly
Glaucoma
What are some importnat drug drug interactions for Muscarinic antagonists like hyoscine hydrobromide? (Given for motion sickness)
Anti psychotics
How do H1 antagonists work to treat motion sickness?
Works centrally, Act on vomiting centre and vestibular nuclei
Inhibiting histmainergic signals from vestibular system to the CTZ in the medulla
What are some examples of H1 antagonists that treat motion sickness?
Cyclizine
Levomepromazine
What are some adverse reactions of H1 antagonists?
Sedation
Anti-muscarinic side effects-dry mouth
Constipation
Urinary retention
Blurred vision
What are some contraindications of H1 antagonists?
Epilepsy
Glaucoma
Urinary retention
Children
Elderly
What are some sedating H1 antagonists?
Diphenhydramine
Cyclizine
Promethazine
What are some non sedating H1 antagonists?
Cetirizine (often given for hay fever/allergic rhinitis)
Fexofenadine
Loratidine
Who is motion sickness most common in?
Women. And children
Those who have migraines
What are some conservative managements of motion sickness?
Hydration
Pistioion in vehicle
Distraction
What are some drugs given for motion sickness?
Anitmuscarinics - hyoscine
Anti histamines - Cyclizine, cinnarizine, prochlorperazine
What are some receptors located in the CTZ?
D2 (dopamine)
NK1
5HT3
What is an example of a D2 receptor antagonist?
Metoclopramide
What affects do D2 receptor anatogonsists like metoclopramide have?
CENTRAL DOPAMINE ANATAGONIST BUT PERIPHERAL CHOLINERGIC AGONIST:
Inc ACh at M receptors in gut promoting gastric emptying
Inc tone at lower oesophageal sphincter ROS it closes
Inc tone and amplitude of gastric contractions
Dec tone of pyloric sphincter
Inc peristalsis
What are some adverse drug reactions of metoclopramide?
Depression
Diarrhoea
Drowsiness
Hypotension
Glactorrhoea
Extra pyramidal effects (dystopia)
Parkinsonism
What are some contraindications to metoclopramide?
Post GI surgery
Gi obstruction
Gi perforation
GI haemorrhage
What is the D2 receptor antagonist domperidone good for?
Improving lactation in breastfeeding mothers
What are the adverse effects of domperidone?
Dry mouth
Long QT and VT (cardiac side effects)
Loss of libido
What are some contraindications of domperidone?
Patients over 60 with arrhythmias
What is an example of a D2 receptor antagonist which is an anti-psychotic?
Haloperidol
Prochlorperazine, chlorpromazine
What part of the brain does Haloperidol act on?
CTZ
What are the adverse drug reactions of haloperidol?
Parkinsonism
Movement disorders
Long QT
Arrhythmias
Constipation
Dry mouth