Gastrointestinal Flashcards
What drug class is Gaviscon?
Alignate and Antacid
What is Gaviscon indicated for?
GORD symptomatic relief
Dyspepsia - short term relief
How do antacids work?
Buffer stomach acids
How do alignates work?
Increase viscosity of stomach contents
React with stomach acid to form a floating raft which separates contents from gastro-oesophageal junction
Name an alternative to Gaviscon?
Peptac
What are the side effects of compound alignates?
Magnesium salts
-Diarrhoea
Aluminium salts
-Constipation
What are the contraindications of compound alignates?
Not given to infants with thickened milk preparations
Renal failure
Important drug interactions of compound alignates?
Antacids can reduce serum concentrations of many drugs e.g. ACEi, Cephalosporins, Digoxin, PPI etc
Need to take at different times to these drugs
What drug class is Ranitidine?
Histamine H2 receptor antagonists
What are H2 receptor antagonists indicated for?
Peptic Ulcer disease
GORD
How do H2 receptor antagonists work?
Reduce gastric acid secretion
Can do this as acid comes in via the proton pump
Histamine among other substances regulates the pump
What are the side effects of H2 receptor antagonists?
Few side effects
What are the contraindications of H2 receptor antagonists?
Reduce dose in renal impairment
They can disguise symptoms of gastric cancer
Important drug interactions of H2 receptor antagonists?
None
What drug class is Omeprazole?
PPI
What are PPIs indicated for?
Prevention and treatment of Peptic Ulcer Disease
Symptomatic relief of Dyspepsia and GORD
H. Pylori infection
How do PPIs work?
Irreversibly inhibit the proton pump of gastric parietal cells almost completely
What are the side effects of PPIs?
GI disturbance
Headache
Prolonged treatment hypomagnesaemia
What are the contraindications of PPIs?
Can disguise symptoms of gastric cancer
Can increase the risk of a fracture - so Osteoporosis
Important drug interactions of PPIs?
Omeprazole acts on P450 and can reduce antiplatelet effect of Clopidogrel
What drug class is Loperamide?
Antimotility drug
What are Antimotility drugs indicated for?
Diarrhoea
How do Antimotility drugs work?
Opioid - (other opiods have similar effects but loperamide has no analgesic effect)
It is an agonist of the opioid receptors in the GI tract
Reduces peristalsis
Increases non-propulsive contractions
Transit of bowel contents is slowed and anal sphincter tone is increased
What are the side effects of Antimotility drugs?
GI effects
What are the contraindications of Antimotility drugs?
Acute ulcerative colitis
C Dif colitis
Dysentery - risk of HUS with E. Coli O157
Important drug interactions of Antimotility drugs?
None
What drug class is Senna?
Stimulant Laxative
What are the types (5) of laxatives?
Bulk-forming Stimulant Osmotic Lubricant Stool-softener
What are laxatives indicated for?
Constipation
As suppositories for faecal impaction
How do stimulant laxatives work?
Increase water and electrolyte secretion
Increase volume of colonic content
Stimulating peristalsis
What are the side effects of stimulant laxatives?
Abdominal Pain
Cramping
What are the contraindications of stimulant laxatives?
Intestinal obstruction can lead to perforation
Haemorrhoids - avoid suppository
Anal fissure - avoid suppository
Important drug interactions of stimulant laxatives?
None
What drug class is Mesalazine?
Aminosalicylates
What are Aminosalicylates indicated for?
Mesalazine - Ulcerative Colitis
Sulfasalazine - Rheumatoid Arthritis - used as DMARD
How do Aminosalicylates work?
Ulcerative Colitis:
- Release 5-aminosalicylic acid
- anti-inflammatory and immunosuppressive effects
What are the side effects of Aminosalicylates?
GI upset Headache Leucopenia Thrombocytopenia Renal impairment Oligospermia
What are the contraindications of Aminosalicylates?
Aspirin hypersensitivity - salicylates like aspirin
Important drug interactions of Aminosalicylates?
PPIs increase gastric pH, meaning coating may be broken down prematurely
Lactulose lowers stool pH prevents coating being broken down in colon
What drug class is Metoclopramide?
Antiemetics (dopamine receptor antagonists)
What are dopamine receptor antagonists indicated for?
Prophylaxis and treatment of nausea and vomiting
How do dopamine receptor antagonists work?
There is a vomiting centre in the medulla
Receives inputs from the chemoreceptor trigger zone (CTZ)
Dopamine receptor is the main one in the CTZ
Antagonists don’t trigger this
Also have a prokinetic effect - promote gastric emptying
What are the side effects of dopamine receptor antagonists?
Diarrhoea
Can induce extrapyramidal syndromes - movement abnormalities
What are the contraindications of dopamine receptor antagonists?
Children
Young adults
GI obstruction due to prokinetic effect
Perforation
Important drug interactions of dopamine receptor antagonists?
Antipsychotics have similar effect with extrapyramidal syndromes, so combining is bad
Not combined with dopaminergic agents in Parkinson’s
What type of antiemetic is cyclizine?
Histamine
Side effects with cyclizine?
Drowsiness
Dry throat and mouth due to anticholinergic effects
