Treatment of Vomiting and Gut motility Disorders Flashcards
Neural control of vomiting is where?
- Via two units in the medulla;
1) The vomiting (emetic) centre,
2) The Chemoreceptor Trigger Zone (CTZ)
Describe features of the vomiting centre
- Mainly found in the medullary and pontile reticular formation also extending into spinal cord. It receives nerve impulses from vagal and sympathetic fibres
Describe features of the chemoreceptor Trigger Zone
- It is in the area postrema in the floor of the 4th ventricle. It sensitive to chemical stimuli and is the main site of action of drugs which stimulate vomiting. Mediation of motion sickness
Name some triggers of vomiting
- Stimulation of the sensory nerve endings in the stomach and duodenum,
- Stimulation of the vagal sensory endings,
- Drugs or endogenous emetic substances,
- Stimulation of vestibular apparatus,
- Various stimulus of the sensory nerves of the heart and viscera,
- Rise in intracrainal pressure,
- Nauseating smells, repulsive sights or emotional factors,
- Endocrine factors,
- Migraine
What are the stages of vomiting?
Nausea - Feeling of wanting to vomit, associated with autonomic effects.
Retching - Strong involuntary effort to vomit,
Vomiting - Expulsion of gastric contents through the mouth
What are some types of vomiting
- Projectile vomiting,
- Haematemesis,
- Early-morning
What are some indications for the use of anti-emetic drugs
1) Severe vomiting during pregnancy/hyperemesis gravidarum,
2) Postoperative nausea and vomiting,
3) Motion sickness,
4) Other vestibular disorders,
5) Nausea induced by cytotoxic chemotherapy,
6) palliative care,
7) Associated with migraine
Name the different types of anti-emetic drugs and where they work?
- Antihistamines (H1 receptors in higher cortical centres),
- Antimuscarinics (Works on vestibular nuclei,
- Dopamine antagonists (CTZ),
- 5HT3 Antagonists
- Neurokinin 1 receptor antagonists,
- Synthetic cannabinoids,
- Steroids,
- Neuroleptics
Name features and examples of antihistamines and side effects
H1 Histamine receptor antagonists. Useful in motion sickness and vestibular disorders. Examples are cinnarizine and cyclizine. Side effects are drowsiness and muscarinic effects
Name features and examples of antimuscarinic and side effects
- Causes blockade of muscarinic receptor-mediated impulses from labryinth and from visceral afferents. eg Hyoscine hydrobromide. Side effects are constipation, transient bradycardia and dry mouth
Name features and examples of dopamine antagonists
- Active against CTZ-triggered vomiting but not stomach induced. eg, phenothiazines, chlorpromazine or domperidone
Describe features and name an example of an 5HT(3) antagonists
- Block 5HT(3) receptors in the GI tract and CNS. Manages N/V in patients receiving cytotoxics and postoperative N/V. Eg, Ondansetron
Describe features and name an example of an Neurokinin 1 receptor antagonists
- Adjunct to dexamethasome and a 5HT3 antagonists in preventing N/V associated with chemo, eg, Aprepitant
Describe features and name an example and side effects of an synthetic cannabinoid
Used for N/V caused by chemo unresponsive to conventional anti-emetics. Example is Nabilone. SE - Drowsiness/dizziness
name an example of an steroids antagonists
Dexamthasone.
What are the different types of laxitives and what should be done before prescribing them?
1) Ensure the problem IS constipation,
2) Check the patients norm,
3) Try to reverse the cause.
Different types; Bulk-forming laxatives, stimulant laxatives, faecal softeners (break down particles), osmotic laxatives and peripheral opioid-receptor antagonists
How do bulk flow laxatives work and name an example
They increase stool volume which promotes peristalsis by distention. Example is ispaghula husk
Name an example of a stimulant, softener, osmotic and peripheral opioid receptor antagonist laxatives
Stimulant - Senna,
Softener - Docusate,
Osmotic - Lactulose,
PORA - Methylnaltrexone bromide
What are the approaches for treatment of acute diarrhoea
1) Maintenance of fluid/electrolyte balance via oral rehydration prep.
2) Antimotility drugs (loperamide),
3) Antispasmodics eg, hyoscine butylbromide.
4) Occasionally antibacterial agent needed.
What is used in chronic diarrhoea?
- Antimotility agents eg, loperamide.
- Adsorbents eg, Kaolin,
- Bulk forming drugs eg, ispaghula
What is the treatment for gallstones?
- Ursodexycholic acid if mild symptoms.
- Lap chole and modern endoscopic techniques
Describe the treatment for biliary colic and acute cholecystitis
Biliary colic is painful so need for opioid (morphine) or an NSAID (diclofenac). If pain continues or fever develops the need for hospital admission.
Name an example of a bile acid sequestrant and its features
Colestryamine (anion-exchange resin). It forms an insoluble complex with bile acids in the intestine. It relieves pruritus associated with partial biliary obstruction and primary biliary cirrhosis. Can also be used in crohn’s disease and hypercholesterolaemia.
