Gastrointestinal Flashcards
What are the primary goals in treatment of dyspepsia
Symptom relief
- avoidance of causative drugs and food eg chocolate
- GORD: propping up bed, removing belts
- suppression of acid release and mucosal protection
Describe the curative treatment of dyspepsia
Suppression of acid release to allow natural healing and eradication of H pylori infection
Reduction of risk of gastric carcinoma
Describe the mode of action of antacids
Anti acid used to raise pH and treat dyspepsia
Provide rapid relief but not cure
What are alginates
Combined with antacids
Derived from alginic acid and forms a viscous foam when combined with saliva
Floats on the gastric contents forming a raft which protects the oesophagus during reflux
What do histamine H2 antagonists do
Reduce gastric acid secretion
Provide symptomatic relief
Best given at night
Promote ulcer healing
Reduce the need for surgery in ulceration
H1 receptor antagonists are antihistamines
What is the mode of action of PPIs
Act via irreversible inhibition of the proton pump
They are activated by acidic pH
What are some adverse effects of PPIs
Inhibit H+ secretion by >90% which can lead to achlorhydria and increase risk of campylobacter infection
Why should alcohol be avoided when taking metronidazole
Metronidazole inhibits the breakdown of alcohol at the aldehyde stage
What are ways of minimising GI damage
Use paracetamol for analgesia
Identify pts at risk eg over 65, history of ulcers
Prophylaxis with PPI
Use PPI over H2 antagonists as they are less effective
Give in combination with misoprostol - acts on prostanoid receptors to inhibit gastric H+ secretion
Which drugs cause nausea
Anti cancer agents
Digoxin
SSRIs
Opioids
Levodopa
Erythromycin
What is the pathway by which motion causes sickness
Labyrinth acts on the vestibular nuclei (H1 and M receptors)
These act on the chemoreceptor trigger zone D2 and 5HT3 receptors
Which acts on the vomiting centre
How do drugs and toxins cause vomiting
They act directly on the chemoreceptor trigger zone D2 and 5HT3 receptors which acts on the vomiting centre
They can also act on the visceral afferents 5HT3 receptors which acts on the nucleus of the solitary tract which acts directly on the vomiting centre
What is the main anti emetics used
H1 receptor antagonists eg promethazine, cyclizine
Mode of action of H1 receptor antagonists
- act on the vestibular nuclei
- effective in motion sickness
- have anti-muscarinic actions
How do anti muscarinic agents eg hyoscine work
Effective in motion sickness and irritation of the stomach
Have anti muscarinic side effects
How do dopamine antagonists work as anti emetics
Acts in CTZ but has unwanted CNS effects
- effective against anti cancer drug induced Emesis
How do 5-hydroxytryptamine antagonists work
Block 5 HT at 5HT3 receptors in the gut and CNS
Effective against anti cancer drugs and post operative N&V
Give examples of drugs that can cause diarrhoea
Antibiotics: alter lower GI flora, clindamycin associated with pseudomembraneous colitis
Orlistat: pancreatic lipase inhibitor that causes fatty diarrhoea
Misoprostol: via cAMP
PPIs: infection
How is diarrhoea treated
Oral rehydration therapy eg dioralyte
Is a solution of electrolytes to replace the electrolytes lost
Must be isotonic
How can diarrhoea be relieved symptomatically
Antimotility agents
Codeine and loperamide. If infection is present they can prolong the infection and prevent clearance
Why is loperamide used over codeine
Doesnt penetrate BBB and has efficient enterohepatic cycling so retained largely in the GI tract
Codeine has some potential neuro side effects
What is irritable bowel syndrome
A common long standing disorder
Present for at least 3 days per month in the last 3 months:
- abdo pain
- bloating relieved by defecation
- change in bowel habit
What is inflammatory bowel disease
Includes crohn’s and UC
- inflammatory conditions with high degree of morbidity and run relapsing and remitting courses
Causes are unclear
Describe the clinical symptoms of acute gastroenteritis
Diarrhoea >3 loose stools per day
N&V
Abdo pain
Fever
What is dysentery
Bloody diarrhoea
What % of antibiotic associated diarrhoea is C diff positive
20-30%
What % of antibiotic associated colitis is C diff positive
50-75%
What % of pseudomembranous colitis is C diff positive
> 90%
Why are antibiotics not given for travellers bacteria
<80% due to bacteria and are due to a virus
People usually get better by themselves
