Gastrointestinal disease Flashcards
Dyspepsia; Gastric acid secretion; Antacid; Alginate preparations; H2 receptor antagonists; Proton pump inhibitors; Gastro oesophageal reflux disease; Nausea and vomiting; H1 receptor antagonists; anti dopaminergics; 5HT3 receptor antagonists; Constipation; Laxatives; Diarrhoea
What area of the GIT is affected by dyspepsia and what are the 4 main causes?
Symptoms effecting the upper GIT
Caused by underlying conditions, drugs, smooth muscle relaxants and gastric acid
6 symptoms of dyspepsia
Retrosternal/epigastric pain Fullness Bloating Wind Heart burn Nausea/vomiting
3 underlying conditions mistaken for dyspepsia
Peptic ulcer disease
Gastro oesophageal reflux disease
Non-ulcer dyspepsia
6 drugs that can cause dyspepsia
Nitrates Theophyllines Bisphosphonates NSAIDs Corticosteroids Calcium antagonists
Explain why smooth muscle relaxants cause dyspepsia
Cause smooth muscle of oesophageal sphincter to relax allowing stomach contents to rise up and come into contact with unprotected oesophagus
Explain how gastric acid causes dyspepsia
Over production
What cell is gastric acid secreted from and what type of acid is it
Parietal cells by proton pumps
Hydrochloric acid
Name 4 drug groups used for gastric acid
Antacids
H2 receptor antagonists
Alginate preparations
Proton pump inhibitors
3 chemicals that stimulate gastric acid secretion
Histamine
Acetylcholine
Gastrin
What cell produces histamine?
Enterochromaffin like cells (ELC)
What nerve is stimulated to release acetylcholine
Vagus nerve
What cell is gastrin secreted by?
G cells
Explain how gastric acid is secreted?
Gastrin, histamine and acetylcholine all stimulate proton pumps of parietal cells to transport hydrogen ions into the gastric lumen- in exchange for potassium ions.
Chloride and potassium ions passively diffuse out into the gastric lumen.
Gastrin and acetylcholine indirectly stimulate histamine release further stimulating gastric acid production.
4 intrinsic GIT mucosa protective factors
Blood flow
Bicarbonate
Prostaglandins
Mucus
3 aggravating intrinsic factors for GIT mucosa
Refluxed bile
Acid
Pepsin
How do antacids work on dyspepsia symptomatic relief?
Neutralise stomach acid
4 forms antacids come as
Tabs
Liquids
Single agents
Combinations
2 interactions of antacids
Reduce absorption rate from GIT
Interfere with drugs that have enteric coatings
4 ADRs of antacids
Constipation
Diarrhoea
Unpalatable
Alter sodium and aluminium absorption
How do alginate preparations work?
Work as rafting agents, providing a protective coating of the oesophagus wen stomach contents rise up
What condition are antacids used for?
Dyspepsia
What 2 conditions are alginate preparations used for?
Gastro oesophageal reflux disease (GORD)
Dyspepsia
True or false, alginate preparations are safe for use in pregnancy
True - minimal side effects
What time of day are alginate preparations advised to be taken at?
Bed time or with evening meal
2 contraindications for alginate preparations use and why
Hypertensive pts - sodium content of preparation
Diabetic pts - glucose content of preparations
How do H2 receptor antagonists work?
Inhibit histamine H2 receptors reducing production of stomach acid
What 2 conditions are H2 receptor antagonists used for?
Gastro oespophageal reflux disease
Peptic ulcer disease
True or false, H2 receptor antagonists and alginate preparations have few ADRs?
True
How do proton pump inhibitors work?
Inhibit the exchange of protons for potassium ions preventing the production of gastric acid.
What 3 conditions are proton pumps used for?
Gastro oesophageal reflux disease
Peptic ulcer disease
Dyspepsia
5 ADRs of proton pump inhibitors
GIT discomfort Headache Rash x2 increase in risk of C.Diff ? increased risk of osteoporosis
What bacteria causes chronic gastritis?
?gram
Helicobacter pylori
Gram -ve
What % of duodenal ulcers are caused by helicobacter pylori infections?
95%
What % of gastric ulcers are caused by helicobacter pylori infections?
70-80%
What is the treatment for helicobacer infections?
Abx and a proton pump inhibitor
5 causes of gastro oesophageal reflux disease
Bile
Acid
Relaxation/dysfunction of lower oesophageal sphincter
Motility dysfunction of lower oesophageal sphincter
Life style factors
What 2 features of pregnancy increase the incidence of gastro oesophageal disease?
Increased abdominal pressure
Increased progesterone levels that causes smooth muscles to relax
What are the 3 stages of treatment for GORD in pregnancy?
- Alginate preparation
- H2 receptor antagonist
- PPI
What is the treatment for GORD in an infant? And for what duration?
Alginate preparation for 1-2 weeks
What is the treatment for GORD in children and the duration?
H2 antagonist/PPI for 1 month
What is the aim of GORD treatment in adults?
To improve intrinsic factors (prostaglandins, blood flow, bicarbonate, mucus) that protect GIT mucosa and reduce contact of gastric acid with oesophagus
5 non-pharmacological lifestyle alterations to reduce GORD
Stop smoking Loose weight Avoid trigger foods e.g. fats Sleeping with head raised Avoid alcohol
What is the treatment for GORD in adults and duration?
PPI for 1-2 months, titrating down to the lowest dose to treat symptoms.
What are 2 reasons why pt would remain on max dose of PPI?
Severe GORD or strictures
7 causes of nausea / vomiting
Drugs Motion Endogenous toxins e.g. dialysis pt Over indulgence Viral infection Gastroenteritis Migraine
5 classes of anti-emetics
H1 receptor antagonists AchM receptor antagonists Anti-dopaminergics 5HT3 receptor antagonists Others- cannibinoids
What endogenous chemical do H1 receptor antagonists interfere with?
Histamine
What 3 conditions are H1 receptor antagonists most effective for?
Post op nausea and sickness
Motion sickness
Pregnancy sickness
2 ADRs of H1 receptor antagonists
Drowsiness
Antimuscarinic
What are AchM receptor antagonists most effective for?
Motion sickness
2 routes for AchM receptor antagonists
Transdermal patch
Sublingual tablet
3 ADRs of AchM receptor antagonists
Dry mouth
Blurred vision
Sedation
What are 2 subcategories of anti-dopaminergics?
Phenothiazines and butrophenones
How do phenothiazines work?
what area do they inhibit
Inhibit agents that stimulate the chemoreceptor trigger zone
What 2 situations are phenothiazines most effective in treating?
Post op nausea and vomiting
Palliative care nausea and vomiting
How do butyrophenones work?
which receptor do they inhibit where, GIT motility
Work as antagonists on dopamine receptors in chemoreceptor trigger zone.
Increase GIT motility
What are butyrophenones most effective in treating?
Nausea and vomiting associated with chemotherapy
3 ADRs of anti-dopaminergics
Arrythmias
Hyperolactinaemia
Involuntary movements
Mechanism of how antiemetics work
Antagonists stopping propagation of action potentials from nausea/vomiting receptors
How do 5HT3 receptor antagonists work?
Inhibit receptors in the chemoreceptor trigger zone
What are 5HT3 receptor antagonists most effective in treating?
Chemotherapy related nausea/ vomiting
Post op nausea vomiting
What is an ADR of 5HT3 receptor antagonists?
Increase in arrythmias by increasing the QT interval
2 routes of administration for 5HT3 receptor antagonists
Orally
IV
Explain the mechanism of nausea/vomiting
Chemoreceptor trigger zone, located outside the blood brain barrier, able to detect noxious stimuli such as chemicals, ingested substances, endogenous toxins.
Impulses pass from chemoreceptor trigger zone to vomiting centres in the ventricles of the brain.
Vomit centre controls the smooth muscle of the stomach, when stimulated causing the stomach contents to be expelled.
Which structure detects motion sickness?
Vestibular apparatus
4 neurotransmitters involved in nausea/vomiting
Dopamine
Histamine
Acetylcholine
5 hydroxytriptamine
What neurotransmitter do D2 receptors bind to and where are they located?
Dopamine
Chemoreceptor trigger zone
What neurotransmitter do Ach Muscanaric receptors bind to and where are they located?
Acetylcholine
Vomiting centre and vestibular apparatus
What neurotransmitter binds to H1 receptors and where are they located?
Histamine
Vomiting centre and vestibular apparatus
What neurotransmitter binds to 5HT3 receptors and where are they located?
5 hydroxytripramine
Chemoreceptor trigger zone and in GIT
5 causes of constipation
Immobility Inadequate diet Lack of dietary fibre Drugs Disease
4 classes of laxatives
Osmotic
Bulk
Stimulants
Softeners
Name type of bulk laxative and mechanism of effect
Ispagulahusk
Increases faecal mass, increasing the pressure on GIT wall stimulating peristalsis
What is an instruction for use in bulk laxatives?
Stay hydrated
Name type of osmotic laxative and mechanism of effect
Macrogols
Increase influx of water into faecal matter softening stool
2 ADRs of osmotic laxatives
Bloating
Flatulence
How do faecal softeners work?
Increase absorption of water into faecal matter decreasing surface tension
How do stimulant laxatives work?
Stimulate the gut wall increasing GIT motility
ADR of stimulant laxatives
Cramping
4 causes of diarrhoea
Infection
Disease
Drugs
Diet
Treatment for diarrhoea
Fluid and electrolyte replacement, isotonic solution containing glucose, sodium, potassium, chloride and bicarbonate ions
What is the risk electrolyte wise in diarrhoea?
Risk of hypokalaemia caused by dehydration