Clincal CNS Nausea/GA Flashcards
Name the GI causes of vomiting:
Gastro-enteritis
Appendicitis
Peptic ulceration
Gastric carcinoma
Infection (common)
Name organic diseases that cause vomiting:
Renal failure (uraemia)- high levels of this toxin
Diabetic ketoacidosis
Myocardial infarction- occur on inferior wall more likely
Name CNS causes that can cause vomiting:
Migraine
Meningitis
Vestibular disease (Meniere’s)
Name post-op causes that can cause vomiting:
Complex and multifactorial e.g pain, surgery, anaesthesia
What causes motion sickness?
Conflicting info between eyes and body
What are the common ages for motion sickness?
Children less than 1- labyrinth not functional so rarely occurs
Children 3-12 most vunerable
Name common drugs that cause N&V:
Opiates
Antibiotics (doxy)
Digoxin
Levodopa
Aminophylline/theophylline
Chemo
Which methods are N&V caused by?
1 of 2 methods:
Mimicking the action of NT/ changing levels of NT
Activating the abdominal afferent system (peripheral)
Name different type of drugs that mimic/ change NT:
Mimicking action of NT:
Opioids, Ldopa
Changing levels:
5HT3 re-uptake inhibitors (for depression)
Describe how activating the abdominal afferent system can cause N&V:
Delaying gastric emptying
Direct activation of mucosal afferent system
What is Ménière’s disease?
Disorder of the inner ear
Excess fluid on labyrinth canals (hydros)
What is the epidemiology of Ménière’s disease?
0.1% of population, common between 20-50 years old
What are the symptoms of Ménière’s disease?
Incapacitating attacks characterised by:
-giddiness, vertigo, N&V
-hearing loss
-functional paralysis
-tinnitus
Sudden onset, lasts 20mins to several hours
Migraine present in 30%
What is vertigo?
Sensation of rotation or spinning
Patient (objective) or their surrounding (subjective)
What are the common causes of vertigo in different age groups?
Young people- labyrinthitis
Elderly- BPPV
What is BPPV?
Benign Paroxysmal Positional Vertigo
Movement of naturally occurring calcium salts
What are other causes of vertigo?
Head injury
Migraine
MS
Excess alcohol
When should a patient be referred if they have vertigo?
If they have N&V associated
Name some vestibular toxic drugs:
Aminoglycosides e.g gentamicin
Anticonvulsants
Furosemide- max rate 4mg/min- ototoxicity
NSAIDs
Quinine
When does morning sickness occur?
50-90% if women experience nausea during first trimester
Begins shortly after first missed period
Peaks weeks 10-14
Often disappears after 4th month
What is morning sickness due to?
High levels of HCG- human chorionic gonadotropin
Name a severe form of morning sickness:
Hyperemesis Gravidarum
Describe hyperemesis gravidarum:
Severe persistent N&V during pregnancy- can’t keep anything down
Weight loss, dehydration, acidosis, ketosis
1-3 per 1000 deliveries
Untreated can be fatal to mother/foetus/both
What are the reasons for treating N&V?
Highly unpleasant for patient
Dehydration
Weight loss
Renal impairment
Electrolyte abnormalities
Describe the severity of symptoms of N&V that would require referral:
Projectile vomiting- pyloric stenosis
Sour smelling vomiting- pyloric stenosis
Blood in vomit
Describe other symptoms of N&V that would require referral:
Severe diarrhoea/ long duration
-gastro-enteritis, infection
Weight loss
Abdominal pain
-appendicitis, biliary colic, renal colic, hernias
Dizziness
-meningitis, head injury, Meniere’s disease
Describe the onset of action of H1 receptor antagonists:
Act within 2 hours
Theoclate salts longer acting than hydrochloride
Name the MOA of promethazine:
H1 receptor antagonist
Also some D2
Name the SEs of H1 receptor antagonists:
Drowsiness, dizziness, tinnitus
Antimuscarinic, antidopaminergic (promethazine) SEs
What are the CI for promethazine:
Glaucoma and other muscarinic/ dopaminergic
How do antimuscarinics work?
Act on muscarinic (M1 receptors centrally)
Antispasmodic gut action
What are the SEs of anticholinergics?
Drowsiness, dry mouth, dry skin, decreased gut motility
Increased IOP and HR
What are the CI of anticholinergics aka muscarinics?
Glaucoma and urinary retention
How does prochlorperazine work?
Inhibits D2r and also some M1 (muscarininc)
Name SEs of prochlorperazine:
Anti-dopaminergic- extrapyramidal e.g dystonia, dyskinesia, Parkinsonism- all more than chlorpromazine
Anti-cholinergic- drowsiness, blurred vision, dry mouth
How does chlorpromazine work?
D2r antagonist, H1, antimuscarininc
What are the counselling points for chlorpromazine?
More sedative effects than prochlorperazine
Used in palliative care
Contact senitisation- carer don’t touch them
How does metoclopramide work?
Blocks D2R and some 5HT3
Antimuscarininc
Peripherally and centrally
Antiemetic and prokinetic properties (stim gastric emptying)- not in physicsal gut obstruction
What is the dosing of metoclopramide and why?
Max 30mg/day for 5 days (10mg QDS)
Lowest dose for shortest time
Neurological adverse effects- acute dystolic reactions, movement disorders
What are the SEs of metoclopramide?
10% experience transient SEs; drowsiness dizziness, anxiety
Extrapyrmidal SEs e.g dystonia, tardive dyskinesia, oculogyric crisis) more common in 12-19 yrs and females
What are the interactions with metoclopramide?
Cyp2D6 inhibitor
Fluoxetine, paroxetine
Causes increase in metoclopramide
What is the dosing of domperidone and why?
Lowest dose for shortest time- max 1 week due to CV risk
What are the CI of domperidone?
Cardiac disease (irregular HR, QT) or any meds that cause QT prolongation e.g methadone, citalopram, amiodarone
Not in children and those less than 35kg
How does domperidone work?
D2R antagonist- outside BBB
Prokinetic
Antimuscarininc (periphery)
What are the interactions of domperidone?
CYP3A4 inhibitors e.g macrolides, azoles
Leads to higher doses of domperidone
How do 5HT3 antagonists work?
5HT3r located peripherally on vagal nerve endings and vomiting centre- endochromaffin
What are CIs of ondansetron?
QT prolongation drugs or abnormality as can increase risk of ventricular arythmias- congenital long QT syndrome
What are the common SEs of ondansetron?
Constipation, feeling hot, headache, hypotension
QT prolongation
What are the interactions with ondansetron?
Many CYP enzymes such as inducers which increases clearance of ondansetron
What are non pharmacological treatments for nausea and vomiting?
Acupressure
Transcutaneous Electrical Nerve Stimulation (TENS)
What are the first line treatments for morning sickness?
Promethazine
Prochloperazine
Cyclizine
Doxylamine and pyridoxine
Chlorpromazine
What are the second line treatments for morning sickness?
Domperidone
Ondansetron- avoid in first 12 weeks due to orofacial cleafing
Metoclopramide
Describe doxylamine and pyridoxine:
Doxylamine- H1 r antagonist
Pyridoxine- VitB6
Anticholingeric
Only medicine licensed in N&V in pregnancy
Name different antiemetics used for CINV:
Dexamethasone
5HT3 r antagonists for acute and delayed
NK1 antagonists- delayed but can be acute
What are the SEs of dexamethasone?
If BD dosing insomnia SEs at night
Limited SEs as short amount of time used and low doses
What are the SEs/ interactions with NK1 antagonists?
Diarrhoea, fatigue, nausea
Metabolised by CYP3A4
