Drugs to treat disorders of acid secretion Flashcards
What drug classes can be used to treat disorders of acid secretion?
Antacids and alginates
Histamine H2 receptor antagonists
Proton Pump Inhibitors
What is an antacid?
Any substance (generally a base) which counteracts stomach acidity. Act by buffering gastric acid, raising pH
Name 2 examples of antacids
Aluminium Hydroxide + Magnesium Hydroxide (Maalox)
Calcium Carbonate + Magnesium Carbonate (Rennie’s)
What is an alginate?
Anionic polysaccharides that form a viscous gel upon binding water.
Increase viscosity of stomach contents to protect oesophagus from acid reflux.
Name an example of an alginate?
Sodium alginate, sodium bicarbonate, calcium carbonate (Gaviscon)
What is the MoA of Histamine H2-receptor antagonists?
Competitively inhibit histamine receptors on parietal cells
Name 2 examples of Histamine H2-receptor antagonists
Cimetidine (Tagamet)
Ranitidine (Zantac)
What is the MoA of PPIs?
Irreversibly inhibit the H+/K+ ATPase pump (terminal step in acid secretory pathway)
Name 2 examples of PPIs
Omeprazole
Lansoprazole
What conditions would require drug treatment of acid secretion?
Reflux oesophagitis Peptic ulcers (can be caused by NSAID use or H. Pylori infection, amongst others)
What is reflux oesophagitis?
Inflammation of the lower oesophagus produced by persistent episodes of reflux (GORD)
What are the symptoms of reflux oesophagitis?
Heartburn
Regurgitation
Haematemesis (vomiting blood)
What are potential complications of reflux oesophagitis?
Oesophageal ulceration
Peptic stricture
Barrett’s oesophagus
What is the pharmacological management of reflux oesophagitis?
Step 1: Antacids + Alginates (OTC)
Step 2: H2-receptor antagonists (OTC, if above fails)
Step 3: PPIs (prescribed for more severe cases)
How can NSAIDs cause peptic ulcers?
Inhibit prostaglandin synthesis and impair renewal of the gastric mucosal barrier
[Prostaglandins increase mucus and bicarbonate production and inhibit acid secretion]
What precautions can be taken to reduce risk of GI-adverse effects in patients taking NSAIDs?
Alternative drug? Low dose Short duration Frequent review Co-prescription of PPI in high risk patients
What is H. Pylori?
Spiral-shaped, gram-negative bacterium that causes damage to stomach and duodenal tissue
How does H.Pylori cause peptic ulcers?
Secretes Urease - breaks down Urea into CO2 and NH3
NH3 neutralises gastric acid
H.Pylori penetrates mucus barrier
NH3, bacterial products and acid damage epithelial cells
How can H.Pylori be treated?
Long term combination of antibiotics and a PPI
What is hypochlorydria?
Absence/ deficiency of hydrochloric acid in gastric juice
What are the consequences of hypochlorydria?
- Impaired ability to absorb certain nutrients (e.g. iron and B vitamins)
- Increased vulnerability to bacterial infections in the GI tract
What is Zollinger-Ellison Syndrome?
Presence of a gastrin-secreting tumour or hyperplasia of the islet cells of the pancreas causing overproduction of stomach acid and recurrent peptic ulcers
