Nausea and vomiting

Vagal/splanchnic afferents Cerebral cortex Vestibular nuclei CTZ GABA 5HT ACh H1 5HT3 D2 Gut wall Vagal/splanchnic afferents Gastric atony Retroperistalsis Thoracic and abdominal muscle contractions Vomiting centre 5HT3 ACh H1 5HT2

Movement/vertigo Vestibular nuclei CTZ Gastric atony Retroperistalsis Thoracic and abdominal muscle contractions Vomiting centre

Hyponatraemia Fear/anxiety Raised ICP Vestibular nuclei CTZ Gastric atony Retroperistalsis Thoracic and abdominal muscle contractions Vomiting centre

HypercalcaemiaUraemia Morphine Cytotoxic chemotherapy Vestibular nuclei CTZ Gastric atony Retroperistalsis Thoracic and abdominal muscle contractions Vomiting centre

Intestinal Distension Vestibular nuclei CTZ Intestinal Distension Cytotoxic chemotherapy Vomiting centre Gastric atony Retroperistalsis Thoracic and abdominal muscle contractions Abdominal RXT Gastric irritants

Case studies Pick the most appropriate antiemetic in each case

Management Treat reversible causes Remember unrelated causes e.g gastroenteritis Choose the most appropriate antiemetic for the cause Prescribe the same antiemetic regularly and prn If oral absorption in doubt, use sc route Remember non-drug treatments Consider dexamethasone REVIEW

Common anti-emetics Prokinetic for gastric stasis, functional bowel obstruction Metoclopramide 10mg tds or 30-60mg/24hr CSCI Acting on CTZ trigger zone for chemical causes of vomiting eg morphine, renal failure Haloperidol 1.5-3mg stat/nocte or 2.5-5mg sc stat and 2.5-10mg/24hr CSCI

Common anti-emetics Antispasmodic and antisecretory if bowel colic and/or need to reduce GI secretions Buscopan 20mg stat 60 – 120mg/24hr CSCI Acting in the Vomiting Centre for raised ICP, motion sickness or mechanical bowel obstruction Cyclizine 50mg tds 150mg/24hr CSCI Broad-spectrum for mechanical obstruction, or if others fail Levomepromazine 6-12.5mg nocte

Nausea and Vomiting Cause Clinical Picture Rx Metabolic (drugs, uraemia, hypercalcaemia) Persistent nausea Haloperidol Levomepromazine Gastric stasis Occ. nausea relieved by vomiting Metoclopramide Domperidone Bowel obstruction (abdo. ca./autonomic neuropathy) Nausea relieved by vomiting ± colic ± faecal vomit Buscopan/ levomepromazine Cyclizine ↑ ICP, brainstem disease Headache Cyclizine ± dex. Vestibular disease Movement related 1)Cyclizine 2) Levomepromazine Bentley A, Boyd K. Palliative Medicine 2001;15:247-53.

Summary Try to establish the cause and choose an appropriate antiemetic, rather than picking your favourite Avoid combinations that may antagonise each other Choose an appropriate route