GIT - Pharmacology

Question 1

Antacids

Answer 1

• basic (alkaline) compounds that neutralise hydrochloric acid in the stomach
• aglinates contain alginic acid which creates a thick gel that prevents gastric acid rising in the stomach
• indications - gastric hyperacidity, peptic ulcer, reflux, gastritis, heartburn, indigestion, dyspepsia
• preperations - mylanta, gastrogel, alginates - gaviscon, mylanta
• A/E - constipation, diarrhoea, hypercalcaemia, abdominal distention, alkalosis, fluid retention
• considerations - antacids reduce absorption of other meds, binding with them, should not be given within 2 hours of any other medications, need to be shaken well, liquids act faster than tablets
• avoid with constiaption, heart failure, diarrhoea, kidney failure

Question 2

Antiemetics - Dopamine Agonists

Answer 2

• drugs which manage nausea & vomiting

dopamine agonists - block dopamine receptors in the chemoreceptor trigger zone and vomiting centre, decreasing vomiting, can also be prokinetic agents which increase mobility of the upper GI and increase gastric emptying

• common - metoclopramide (maxalon)
• prochlorperazine (stemetil)
• domperidone (motilium)
• A/E maxalon - restlessless, drowsiness, hypotension, tachycardia, extrapyramidal reactions, insomnia
• stemetil - constipation, dry mouth, drowsiness, extrapyramidal reactions, blurred vision
• motilium - abdominal cramping, headache, dizziness, insomnia

Question 3

Anitemetics - 5-HT3 Receptor Antagonists

Answer 3

• block 5-HT3 receptors in GIT and vomiting centres which stimulates to reduce vomiting
• indications - nausea & vomiting related to chemo, postoperative nausea & vomiting
• dolasetron (anzemet)
• ondansetron (zofran)
• tropisetron (naoban)
• A/E - headache, flushing anxiety, dizziness, drowsiness, constipation, abdominal discomfort, hypotension

Question 4

Corticosteroids

Answer 4

• have been found effective for chemotherapy induced nausea
• dexamethasone
• methylprednisolone

Question 5

Proton Pump Inhibitors

Answer 5

• weakly basic drugs that suppress gastric acid secretion by inhibiting the ATPase enzyme system blocking the final stages of acid production
• indications - gastric & duodenal ulcers (used in combination with amoxycillin & clarithromycin), oseophagitis
• esomeprazole (nexium)
• pantoprazole (somac)
• omeprazole (losec)
• A/E - headache, dizziness, abdo pain, GIT disturbance, rash
• readily absorbed from GIT, reaches peak in 3-5hrs

Question 6

Histamine H2-Receptor Antagonists

Answer 6

• block histamine release, histamine release induces H2 receptors to increase gastric acid secretion, blocking receptors decreases volume of gastric acid secretion
• indications - gastric & duodenal ulcer, reflux, oesophagitis
• cimetidine
• ranitidine
• famotidine
• A/E - headache, dizziness, tiredness, diarrhoea, constipation, musculoskeletal pain, rash, confusion
• considerations - should be taken with meals, need to continue treatment for 4-6 weeks, monitor vitals closely if given IV, may inhibit the metabolism of many other medications

Question 7

Cytoprotective Agents

Answer 7

• create a physical barrier over an ulcerated gastric surface by creating a gel for short term management of ulcers
• sucralfate
  
  • composed of sulphated sucrose & aluminium hydroxide
  • acts only in the presence of acid to form a sticky gel that creates a barrier for up to 6hrs
  • A/E - constipation
• misoprostol
  
  • prostaglandin analogue (like what the body produces naturally) that inhibits gastric acid secretion & increases gastric mucus
  • A/E - diarrhoea, abdo pain, dyspepsia, nausea & vomiting, hypotension - not used in pregnant women

Question 8

Antispasmodics

Answer 8

• used to control intestinal smooth muscle spasm, as well as relax smooth muscle in other parts of the body
• antimuscarinic drugs that block muscarinic receptors and reduce contractions
• hyoscine (buscopan)
• mebeverine

Question 9

IBD - Management - Aminosalicylates

Answer 9

• management includes corticosteroids (prednisolone), immunosuppressants & aminosalicylates
• aminosalicylates - prostaglandin inhibitors used to reduce inflammation
• sulfasalazine
• mesalazine
• olsalazine

Question 10

Laxatives

Answer 10

• drugs given to increase the speed of food transit through the bowel
• bulk stimulants
  
  • contain polysaccharide polymers that are not broken down by metabolism, stimulate peristalsis by increasing bulk of stool through water absorption
  • drag water into bowel, makes fecal matter swell, increases bulk, transports through body faster
  • fybrogel, metamucil, lactulose
  • considerations - high oral fluid intake needed
  • A/E - diarrhea, abdo cramping, electrolyte loss
• faecal softening agents
  
  • used to treat constipation & prevent straining
  • ducosate (coloxyl), liquid paraffin (agarol)
  • considerations - liquid paraffin impairs absorption of fat soluble vitamins, can cause anal pruritis, chronic inflammatory reaction
• stimulant laxatives
  
  • promote water accumulation in the bowel & stimulate nerve endings to increase peristalsis
  • bisacodyl, senna
  • considerations - abdo cramping, fluid & electrolyte imbalances
• osmotic laxatives
  
  • osmotically draw fluid into the bowel, increasing volume & accelerating transport of stools
  • preperations based with glycerol, lactulose, sorbitol

Question 11

Anti-diarrhoeal

Answer 11

• reduce symptoms, reduce fluid & electrolyte loss due to diarrhoea, block stimulation of the GIT
• coat intestinal mucosa, blocking causative agents (bacteria, toxins) & allow them to be passed out
• kaomagma
• opioid anti-diarrhoeals
  
  • activate opioid receptors in the intestinal wall & reduce secretions & peristalsis
  • codeine phosphate, diphenoxylate & atropine (lomotil), loperamide (imodium)

Question 12

Bowel Surgery Prep

Answer 12

• depends on procedure
• LWD 2 days prior, strict diet
• clear fluids on day prior
• afternoon before, bowel prep administered