Antiemetic & anticonstipation Flashcards
how we vomit
what triggers the emesis? where do they act?
what drugs r used and where do they act?
Antihistamines
where and how they work?
indications?
SE?
contraindicated in?
Cyclizine, Levomepromazine, Cinnirazine, Promethazine Diphenhydramine,
• Centrally
Acts on the VN
Inhibits histaminergic signals from the vestibular system to the CTZ in medulla
Side effects
• Sedation
• Excitation
• Antimuscarinic–dry mouth, constipation, urinary retention,
• Cardiactoxicity(longQT interval)
Indications:
- Motion sickness – long plane journeys*
- Promethazine – morning sickness in pregnancy*
Not good for:-
• Cyclizine – little old ladies and children
what agents act on visceral afferents in the gut?
- 5HT3 receptor Antagonists
- D2 receptor antagonists
Serotonin (5HT) function 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
5HT3 receptor Antagonists
Ondansetron, Granesitron, Palonosetron
(dan is happy)
Peripherally
• Reduces GI motility
• Reduces GI secretions
Centrally
• Acts to inhibit the CTZ
Indication
• Almost everyone – it’s often the 1st line treatment
Side effects - uncommon
- Constipation
- Headache
- Elevated liver enzymes
- Long QT syndrome
- Extra-pyramidal
- effects – dystonia, parkinsonism
- D2 receptor antagonists
(acting on visceral afferents in the gut )
acting on visceral afferents in the gut
Metaclopramide
- Increases Ach at muscarinic receptors in the gut
- Promotes gastric emptying
↑ tone at lower oesophageal sphincter so it closes
↑ tone and amplitude of gastric contractions
↓ tone of pylorus so it opens
• Increases peristalsis
Indication-
- GORD
- Ileus
Side effects
- Galactorrhoea via prolactin release
- Extra-pyramidal effects – dystonia, parkinsonism
DONT USE IF RISK OF OBSRUCTION OR PERFORATION
Domperidone
Similar mechanism as metoclopramide
BUT has increased risk of significant cardiac side effects.
- Good for:-
- Improving lactation in breastfeeding mothers
Side effects
- Sudden cardiac death (long QT and VT)
- Galactorrhoea
D2 receptor antagonists
acting on the CTZ
Prochlorperazine, Chlorpromazine, Levomepromazine, Haloperidol
May also block H1 and Muscarinic receptors
Indication
- Motion sickness, vertigo.
Prochlorperazine in pregnancy
• Haloperidol
Act on the CTZ
Indication:- chemotherapy and palliation
Side effects
• Extra-pyramidal effects – dystonia, parkinsonism
- Sedation
- hypotension
Corticosteroids
where and how they work?
indications?
SE?
Dexamethasone, Methylprednisolone
Assumed to act on the CTZ
• May also have properties of D2 receptor antagonists
Indications
• Perioperative nausea and vomiting
- Chemotherapy
- Palliation
Side effects
• Insomnia
↑ appetite
↑ blood sugar
Cannabinoids
- where and how they work?
- indications?
- SE?
Nabilone
- Assumed to act on the CTZ
- Good for chemotherapy - used as last line
Side effects
• Dizziness
• Drowsiness
- Neurokinin 1 receptor antagonists
- where and how they work?
- indications?
- SE?
- contraindicated in?
Aprepitant, Fosaprepitant, Netupitant
- Prevent the action of substance P at CTZ and in peripheral nerves
- Boosts effects of 5HT3 receptor antagonists
- Anxiolytic and antidepressant properties
indication:
chemotherapy – particularly for delayed emesis
Side effects
• Headache
• Diarrhoea/constipation
• Stevens-Johnson
syndrome
Motion Sickness
- Hyoscine hydrobromide is 1st line
but if ur sailing or driving a boat and u cant be sedated…..
- Cinnirazine typically has fewer side effects
what r Prokinetics & Useful for GORD& Ileus ?
when should it not be used?
Domperidone, Metaclopramide (Cisapride)
Don’t use
• Obstruction
• Risk of perforation
most gut pathologies or obstruction causing emesis?
what is Hyperemesis Gravidarum? what causes it? risk in? treatment>
- 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 $
Chemotherapy treatment antiemetic
Post operative nausea and vomiting managment?
antifidiharreal?
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.
Side effects
- Paralytic ileus
- N & V
- Sedation & Addiction (codeine and morphine)
Types of anticonstipating drugs?
- Osmotic
- Stimulants/irritants
- bulk forming
- stool softeners
- lubricants
Osmotic Laxatives
Increase the amount of water in the large bowel
Draw fluid in>> Lactulose
OR
Retain the fluid they came with>> Macrogols/Movicol
Stimulant 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
Bulk forming laxatives
Ispaghula husk, Methylcellulose
form gels in the colon causing water retention & distension! > oincreased peristalsis
Stool Softeners / lubricants
Docusate sodium, Glycerin suppository, Arachis oil ,Liquid paraffin, mineral oil
- Decrease surface tension of stool
- Increase penetration of fluid into stool
stool softeners takes days to work, often used as prohpylaxis rather than acute treatment
