Antemetis Nd Antidiarrhoeals Flashcards
What is vomiting
Involuntary, forceful expulsion of gastric contents through the mouth
What is the difference between vomiting and regurgitation
S
What are teh process that occur in vomiting
Vomiting Centre in Medulla signals to vomit
1. Nausea, salivation, sweating
Ss
What us the CTZ and what triggers it?
Chemoreceptor Trigger Zone (CTZ)
Sensory afferent s, vestibular nuclei, direct triggers, visceralal afferent s from gut
What are some anti emetic drugs
Ss
What drugs act on the vestibular nuclei
- Muscarinic receptor Antagonists - H1 receptor antagonists
Describe muscaring receptor antagonists
• Competitive blockade of muscarinic acetylcholine receptors
• In the vestibular nuclei
• Also at the CTZ
• Remember these receptor are all over the
body – part of the parasympathetic nervous system!!
• Good for :-
• People who can’t take tablets
• Motion sickness
• Bowelobstruction
What are the side effects os muscariic antagonists
Side effects • Sedation • Memoryproblems • Glaucoma • Dry mouth and constipation
What are the effects h1 antagonists
• Centrally
• Acts on the vestibular nuclei
• Inhibits histaminergic signals from the vestibular system to
the CTZ in medulla
- Good for :-
- Motion sickness – long plane journeys
- Promethazine – morning sickness in pregnancy
- Not good for:-
- Cyclizine – little old ladies and children
What are the side effects of h1 antagonists
Side effects • Sedation • Excitation • Antimuscarinic–dry mouth, constipation, urinary retention, • Cardiactoxicity(longQT interval)
What are agents acting on visceral afferent s
- 5HT3 receptor Antagonists - D2 receptor antagonists
Descrive serotonin in the gut
- 95% serotonin in the body is located in the gut
- Produced by the enterochromaffin cells
- In response to parasympathetic stimulation, serotonin excited enteric neurones
- Smooth muscle contraction increases motility (except in the stomach)
- Increases gut secretions
- Regulates appetite
How to 5ht3 receptor antagonists acts
- Peripherally
- ReducesGImotility
- ReducesGIsecretions
- Centrally
- Acts to inhibit the CTZ
- Goodfor:-
- Almost everyone – it’s often the 1st line treatment
What are the side effects o 5ht3 receptor antagonists
Side effects - uncommon • Constipation • Headache • Elevated liver enzymes • Long QT syndrome • Extra-pyramidal effects – dystonia, parkinsonism
Describe d2 receptor antagonists
Metaclopramide
• Increases acetylcholine at muscarinic receptors in the gut
• Promotesgastricemptying
• ↑ tone at lower oesophageal sphincter so it
closes
• ↑ tone and amplitude of gastric contractions
• ↓ tone of pylorus so it opens
• Increases peristalsis • Goodfor:-
• GORD • Ileus
What are the side effects ofetaclopramide
Side effects
• Galactorrhoeavia prolactin release
• Extra-pyramidal effects – dystonia, parkinsonism
What is domperidone
Domperidone
• Similar mechanism as metoclopramide
• Used to be used very frequently BUT new
evidence and a few high profile cases showed an increased risk of significant cardiac side effects.
• Goodfor:-
• Improvinglactationinbreastfeeding
mothers
What are the side effects of domperidone
Side effects
• Sudden cardiac death (long QT and VT)
• Galactorrhoea
What agents act on the ctz
- 5HT3 receptor antagonists
- H1 receptor antagonists
- Muscarinic receptor antagonists
- D2 receptor antagonists
- Corticosteroids
- Cannabinoids
- NK1 receptor antagonists
Descrube “the zines” action and usage
D2 antagonists • The ‘zine’s = • Act on the CTZ • May also block H1 and Muscarinic receptors • Good for - Motion sickness, vertigo. Prochlorperazine in pregnancy Prochlorperazine Chlorpromazine Levomepromazine
What is haloperidol and when is it used?
D2 antagonist
• Haloperidol
• Act on the CTZ
• Good for :- chemotherapy and palliation
What are the side effects of “the zines” and haloperidol?
Side effects
• Extra-pyramidal effects – dystonia, parkinsonism - USE WITH CAUTION
• Sedation
• hypotension
haloperidol also - sick, anxious, agitated
Describe the action and usage of corticosteroids
Dexamethasone Methylprednisolone • Assumed to act on the CTZ • May also have properties of D2 receptor antagonists
- Good for:-
- Perioperative nausea and vomiting
- Chemotherapy
- Palliation
What are the side effects of corticosteroids
Side effects
• Insomnia
• ↑ appetite - ive if people dont eat bc nausea
• ↑ blood sugar
What are cannabinoids
syntehitc analouge of cannabis NAbilone • Assumed to act on the CTZ • Good for chemotherapy - used as last line
What are the side effects of cannabinoids
Side effects
• Dizziness
• Drowsiness
What are neurokinin 1 antagonists
Aprepitant
Fosaprepitant
Netupitant
• Prevent the action of substance P (excitatory neurotransmitter) at CTZ and in
peripheral nerves
• Boosts effects of 5HT3 receptor antagonists - synergistic, useful in chemo)
• Anxiolytic and antidepressant properties
• Good for chemotherapy – particularly for delayed
emesis (good fot anxiety and depression)
What are some other random drugs used as anti emetics
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Whats is typically used to treat motion sickness
Hyoscine hydrobromide is 1st line (but potentially sedating)
Cinnirazine typically has fewer side effects
Pick the drug based on side effet profile
When is a nasogastric tube used?
Drain stomach and decrompress without them needing to vomit
What are prokinetics?
Prokinetic agents, or prokinetics, are medications that help control acid reflux. Prokinetics help strengthen the lower esophageal sphincter (LES) and cause the contents of the stomach to empty faster.
Domperidone
Metaclopramide
Chewing gum can mimic eating and stimulate gut
When are prokinetics used?
Useful for • GORD • Ileus
Don’t use • Obstruction • Risk of perforation due to inrceased peristalsis
What are drugs used to trreat nausea and vomiting due to GI pathology
Ondansetron
and/or
Cyclizine
then add
Dexamethasone
What are direct triggers of the ctz
Hormones – hyperemesis gravidarum • Drugs • Chemotherapy • Anaesthetics • Opiates • Many others!
What is hyperemesis gravidarum
- Rapid rise in ẞhcg stimulates the CTZ
- Typically weeks 4-16 but may continue beyond
- Higher risk with multiple pregnancies
• More than just ‘morning sickness’ – dehydration, 5%
weight loss, electrolyte imbalance, urinary ketones
Causes nausea and comiting, common in first trimester
True hyperemesis gravidarum can come with dehydration and weight loss - using drugs can be helpful. Normal morning sickness - oral rehydreation
What drugs are typicallly used in hyperemesis gravidarum
Promethazine - H1 receptor antagonist
or
Prochlorperazine - D2 receptor antagonist
then add
Metaclopramide - D2 receptor antagonist
then add
Ondansetron - 5HT3 receptor antagonist
what are some chemo drugs that can cause emesis
ss
what drugs are used for different risks of emesisi with chemotherapy
ss
What are some patient factor which increase wisk of post opertaive nausea and vomiting
Female, history of ponv or motion sickness, younger age, non smoker
What are some anaesthetic risk factors in post operatove nausea and vomititng
general > regiona, use of volatile anaesthetic gases or nitrous oxide, post operative opioids
What are some risk factors for post operative NV to do with the nauture of the surgert
duration of operation, laparoscopic surgery
What drusg are used for PONV
Low Risk
Wait and see!
Moderate Risk
Pick 1 or 2 antiemetic agents
High Risk
pick more than 2 antiemetic agents
If prophylaxis fails – use an antiemetic from another class
What is diarrhoea
Diarrhoea is defined as the passage of three or more loose or liquid stools per day
Consider consistency, frequencyy, comparison to normal
What is infective gastroenteritis
Viral, bacterial or protozoal
May be toxin mediated
Osmotic or Secretory
What are the mechanisms by which diarrhoea can be treated
Treat the cause!
Increase transit time - stool has more ocntact with gut - better hydration, better comfort
Comfort
Prevent incontinence (looser stool - more prone to incontinence)
name a class of drugs used as antidiarrhoeals, and give 3 examples
opiod receptor antagonist - loperamide, codeine, morphine
Describe the action of loperamide
Opioid receptor agonist
Loperamide – specific to μ receptors in the myenteric plexus
• Decreases tone of longitudinal and circular smooth muscle
• Reduces peristalsis but increases segmental contractions
• Decreases colonic mass movement by supressing gastrocolic reflex.
Different people need different doses
Describe teh actions of codeine and morphine as anti diarrhorals
Codeine and morphine - μ and δ receptors
Similar effects to loperamide
More often used when patients have pain also
What are teh side effects of opioid receptor agonists
Side effects • Paralytic ileus • Nausea and vomiting • Sedation and Addiction (codeine and morphine)
What is the constipatign diet
For those with long term loose stools
- IBS, IBD, short bowel, hypermotility, drug side effect
Bananas - High in potassium and fibre (fibre bulks the stool)
White Rice - Binds stool
White bread/pasta - Low in fibre
Limit fruit to 3 portions per day
Avoid caffeine, sorbitol, fatty or spicy foods and fizzy drinks
Consider Probiotics Re-instate a balanced intestinal flora
What are some diet and lifestyle changes to help constipation
14% Prevalence of Chronic Idiopathic Constipation
Drink more water!
Increase fibre intake
- wholegrain foods, fruit & veg, nuts, pulses.
Regular exercise
Toilet routine and positioning
What are some medications ofr constipation
LAxatives: Osmotic (mush) stimulants (push) bulk forming stool softeners
Enemas
Osmotic (Draw water in)
Stimulants (move contents though)
What are osmotic laxatives
Lactulose, movicol, cosmocol
Increase the amount of water in the large bowel
Osmotically raw fluid in Lactulose
OR
Retain the fluid they came with Macrogols - needs to be enough fluid around
Describe stimualnt laxatives
Bisacodyl Sodium Picosulphate Senna Co-Danthromer Docusate Sodium (Glycerin)
Increase intestinal motility
May be given orally or per rectum
Docusate sodium acts as stimulant and stool softener
Glycerin suppositories cause rectal irritation and lubrication
What are bulk forming laxatives
Ispaghula husk
Methylcellulose
They are medicinal fibres
What are stool softeners
Decrease surface tension of stool
Increase penetration of fluid into stool
Docusate sodium
Glycerin suppository
Arachis oil
Liquid paraffin
