GI Flashcards
Name 2 anatacids
Gavisgon and peptac
What is the mechanism by which antacids work?
Contain alginate and >1 anatacid e.g. sodium bicarb, calcium carb, magnesium or aluminium salts
Buffer stomach acid and increase stomach viscosity, reducing damage to mucosa and preventing GORD
Might also inhibits pepsin production
What are the indications for antacids?
- GORD
2. Dyspepsia
What are the CIs for antacids?
Usually well tolerated and safe in pregnancy
Avoid combo with thick, milk preperations - may thicken stomach contents, causing bloating and nausea
Caution Na/K containing antacids in hyperK+/fluid overload
What are the SEs of antacids?
Few, depends on preparation.
Aluminium salts may cause constipation
Magnesium salts may cause diarrhoea
What are the interactions of antacids?
Alginate may bind to drugs and reduce their concentration
Antacids may increase the concentration of drugs by reducing stomach acid
When should antacids be taken?
Just after meal, before bed or when Sx occur
Should antacids be used long term?
No - temporary measure. Discuss lifestyle for why GORD is occurring
Name one H2 receptor antagonist
Ranitidine
What is the mechanism by which H2 receptors work?
Histamine (released by local paracrine cells) regulate parietal cell proton pumps that exchange K+ for H+ into the lumen
Ranitidine blocks histamine receptor so reduces gastric acid secretion
However, proton pump can be activated through different mechanisms so H2 blockers do not completely stop gastric acid secretion
What are the indications for H2 receptor antagonists?
- GORD/dyspepsia - relieves Sx. Alternative treatment = PPIs which are often preferred
- Peptic ulcer - prevention and treatment of gastric, duodenal and NSAID associated ulcers. PPIs usually preferred
What are the CIs for H2 receptor antagonists?
- May disguise Sx of gastric cancer - should fully investigate cause of Sx
- Renal impairment - dose reduction
What are the SEs of H2 receptor antagonists?
Few
May cause GI upset (e.g. diarrhoea or constipation)
Headache
Dizziness
What are the interactions of H2 receptor antagonists?
No major drug interactions
How is H2 receptor antagonists excreted?
Renally
What should patients avoid when taking H2 receptor antagonists?
Alcohol and smoking.
Name 3 proton pump inhibitors
Omeprazole, pantoprazole, lansoprazole
What is the mechanism by which PPIs exert their action
Irreversibly block the H+/K+ ATPase channels of gastric parietal cells, thereby reducing gastric acid secretion
What are the indications for PPIs?
- Peptic ulcer - prevention and Tx of gastric and duodenal ulcers (including NSAID associated)
- Dyspepsia and GORD - treatment of
- Eradication of H Pylori Infection (in addition to ABx)
What are the CIs for PPIs?
- May disguise the symptoms/signs of gastric cancer - should explore warning/red flag signs
- Increased risk of # in elderly (osteoporosis)
- Increases absorption of digoxin
- Dose reduction in hepatic impairment
What are the SEs of PPIs?
- Gastric upset and headache
- Increased gastric pH - reduced host defences may result in infection, particularly in elderly - C Diff
- Hypomagnesia - arrhythmia/tettany
- Hypersecretion of gastric acid upon secretion
What are the interactions of PPIs?
Increase absorption of digoxin
CYP450 inhibitor e.g. reduce platelet reducing effect of clopidogrel, increase risk of bleeding with warfarin
How are PPIs excreted?
Renally
Name 2 anti-motility/anti-diarrhoea drugs?
Loperamide (imodium), codeine phosphate
What is the mechanism by which loperamide/codeine phosphate (anti-diarrhoreals) worK
- Inhibit opioid ų-receptors in GI system - reduces peristalsis and smooth muscle tone.
- Increases bowel transit time and increases anal sphincter tone
- Increases time for water absorption (hardens stools)
What are the indications for loperamide/codeine phosphate?
- Diarrhoea - in context of IBS or gastroenteritis
What are the CIs for loperamide/codeine phosphate?
- Acute ulcerative colitis - reducing peristalsis increases risk of megacolon/perforation
- C Diff infection (may signify infection)
- Acute bloody diarrhoea (dysentry) - may signify infection. Particularly relevant for E Coli 0157 (haemolytic uraemia syndrome; HUS - anti-mobility drugs increases risk)
What are the SE’s of loperamide/codeine phosphate?
Predictable
- Constipation
- Abdo cramping
- Flactulence
What are the interactions of loperamide/codeine phosphate?
No significant interactions
Name one stimulant laxative
Senna
What is the mechanism by which stimulant laxatives work?
- Increase H2O and electrolyte secretion from mucosa into lumen. Increases volume of intestinal contents and peristalsis.
- Pro-peristaltic action - senna broken down by bacteria in gut. Metabolites act directly on enteric nervous system. Increases peristalsis.
What are the Indications for stimulant laxatives
- Constipation
2. Suppositories for faecal impaction
What are the SEs of stimulant laxatives?
- Diarrhoea
- Abdo pain/cramping
- Melanosis Coli - pigmentation of intestinal wall with chronic use
What are the CI for stimulant laxatives?
- GI obstruction - may increase risk of perforation
2. Anal fissures/haemorrhoids - avoid rectal preparations
What are the possible drug interactions for stimulant laxatives?
No clinically significant drug interactions
Name one Aminosalicylates
Mesalazine
What is the mechanism by which aminosalicylates work?
Exert therapeutic effect by releasing 5-ASA
Unknown mechanism but has anti-inflammatory and immunosuppressive effect in the gut
What are the indications for aminosalicylates?
- 1st line treatment for ulcerative colitis and remission of Crohn’s disease
What are the CIs for aminosalicylates
- Contain salicylates (like aspirin) - contraindicated in individuals with hypersensitivity to aspirin
- Renal impairment
What are the SEs of aminosalicylates?
- Headache
- GI disturbance
- Blood abnormalities (rare for serious e.g. leucopenia, thrombocytopenia
- Hypersensitivity reaction
- Renal impairment
What are the drug interactions for aminosalicylates?
- Has pH sensitive coating which may react with other drugs that alter drug pH e.g. PPIs
Lactulose reduce pH in stools. May prevent release of 5ASA in the colon
How are aminosalicyltes eliminated?
Renally
Name one anti-emetic
metoclopramide
What is the mechanism by which metoclopramide/anti-emetics work?
Act on various receptors that input into the vomiting centre of the medulla of the brain
- Block dopamine (D2) receptors of the chemoreceptor trigger zone and gut
- Block histamien and acetylcholine receptors of the vomiting centre and the vestibular system
What are the indications for metoclopramide/anti-emetics?
- Treatment and prophylaxis of nausea and vomiting in wide range of scenarios e.g. vertigo
- First generation antipsychotics (atypical) treatment of psychotic disorders e.g. schizophrenia
What are the contraindications for the use of metoclopramide/anti-emetics?
- Sedative effect and potentially hepatotoxic (hepatic failure and drivers, elderly etc)
- Those who are susceptible to anti-cholinergic side effects e.g. prostatic hypertrophy - may cause urine retention
- reduce in the elderly
What are the side effects of anti-emetics/metoclopramide?
- Drowsiness/sedation
- Gynaecomastia
- Postural hypotension/dizziness
- Movement abnormalities:
Short term Tx - acute dystonic
disorders e.g. oculogyric crisisLong term Tx - extrapyramidal symptoms e.g. Tardive dyskinesia (irreversible, involuntary movements of face, body and limbs)
- Prolong QT interval (like antipsychotics)
What are drug interactions of anti-emetic/metoclopramide?
- Anything that prolongs the QT interval e.g. anti-psychotics, SSRIs, ciprofloxin, macrolides, quinines
- D2 containing drugs
- Parkinson drugs
How are anti-emetics/metoclopramide eliminated?
Renally