Treatment of Vomiting and Gut motility Disorders

Question 1

Neural control of vomiting is where?

Answer 1

• Via two units in the medulla;
  1) The vomiting (emetic) centre,
  2) The Chemoreceptor Trigger Zone (CTZ)

Question 2

Describe features of the vomiting centre

Answer 2

• Mainly found in the medullary and pontile reticular formation also extending into spinal cord. It receives nerve impulses from vagal and sympathetic fibres

Question 3

Describe features of the chemoreceptor Trigger Zone

Answer 3

• 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

Question 4

Name some triggers of vomiting

Answer 4

• 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

Question 5

What are the stages of vomiting?

Answer 5

Nausea - Feeling of wanting to vomit, associated with autonomic effects.
Retching - Strong involuntary effort to vomit,
Vomiting - Expulsion of gastric contents through the mouth

Question 6

What are some types of vomiting

Answer 6

• Projectile vomiting,
• Haematemesis,
• Early-morning

Question 7

What are some indications for the use of anti-emetic drugs

Answer 7

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

Question 8

Name the different types of anti-emetic drugs and where they work?

Answer 8

• 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

Question 9

Name features and examples of antihistamines and side effects

Answer 9

H1 Histamine receptor antagonists. Useful in motion sickness and vestibular disorders. Examples are cinnarizine and cyclizine. Side effects are drowsiness and muscarinic effects

Question 10

Name features and examples of antimuscarinic and side effects

Answer 10

• 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

Question 11

Name features and examples of dopamine antagonists

Answer 11

• Active against CTZ-triggered vomiting but not stomach induced. eg, phenothiazines, chlorpromazine or domperidone

Question 12

Describe features and name an example of an 5HT(3) antagonists

Answer 12

• Block 5HT(3) receptors in the GI tract and CNS. Manages N/V in patients receiving cytotoxics and postoperative N/V. Eg, Ondansetron

Question 13

Describe features and name an example of an Neurokinin 1 receptor antagonists

Answer 13

• Adjunct to dexamethasome and a 5HT3 antagonists in preventing N/V associated with chemo, eg, Aprepitant

Question 14

Describe features and name an example and side effects of an synthetic cannabinoid

Answer 14

Used for N/V caused by chemo unresponsive to conventional anti-emetics. Example is Nabilone. SE - Drowsiness/dizziness

Question 15

name an example of an steroids antagonists

Answer 15

Dexamthasone.

Question 16

What are the different types of laxitives and what should be done before prescribing them?

Answer 16

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

Question 17

How do bulk flow laxatives work and name an example

Answer 17

They increase stool volume which promotes peristalsis by distention. Example is ispaghula husk

Question 18

Name an example of a stimulant, softener, osmotic and peripheral opioid receptor antagonist laxatives

Answer 18

Stimulant - Senna,
Softener - Docusate,
Osmotic - Lactulose,
PORA - Methylnaltrexone bromide

Question 19

What are the approaches for treatment of acute diarrhoea

Answer 19

1) Maintenance of fluid/electrolyte balance via oral rehydration prep.
2) Antimotility drugs (loperamide),
3) Antispasmodics eg, hyoscine butylbromide.
4) Occasionally antibacterial agent needed.

Question 20

What is used in chronic diarrhoea?

Answer 20

• Antimotility agents eg, loperamide.
• Adsorbents eg, Kaolin,
• Bulk forming drugs eg, ispaghula

Question 21

What is the treatment for gallstones?

Answer 21

• Ursodexycholic acid if mild symptoms.

- Lap chole and modern endoscopic techniques

Question 22

Describe the treatment for biliary colic and acute cholecystitis

Answer 22

Biliary colic is painful so need for opioid (morphine) or an NSAID (diclofenac). If pain continues or fever develops the need for hospital admission.

Question 23

Name an example of a bile acid sequestrant and its features

Answer 23

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.