Drugs to Treat Disorders of Acid Secretion Flashcards
What are the 3 main classes of drugs used to treat disorders of acid secretion?
- Antacids and alginates
- Histamine H2-receptor antagonists
- Proton pump inhibitors
What is an antacid in terms of medication to treat disorders of acid secretion?
Any substance, generally a base, which counteracts stomach acidity.
What effect do antacids have on Pepsin? Why is this?
Antacids inhibit Pepsin activity, because Pepsin is activated by exposure to a low pH, but antacids raise the gastric pH by buffering gastric acid.
List 2 brands of antacids and their active ingredients.
- Rennie - Calcium carbonate and magnesium carbonate.
2. Maalox - Aluminium hydroxide and magnesium hydroxide.
Magnesium salts used in antacids can also cause which other side effect?
Diarrhoea.
Aluminium salts used in antacids can also cause which other side effect?
Constipation.
What are alginates?
Anionic polysaccharides that form a viscous gel upon binding with water.
When combined with antacids, alginates are particularly good at preventing which common gastric complaint?
Reflux oesophagitis/ acid reflux/ GORD.
What is the drug class of Rennie and Maalox?
Antacids.
What is the drug class of Gaviscon?
Antacid + alginate.
What are the active ingredients in Gaviscon?
Sodium alginate, sodium bicarbonate, calcium carbonate.
What is the MOA of histamine H2-receptor antagonists?
Competitively inhibit histamine actions at H2-receptors.
What is the name of the histamine receptor on Parietal cells of the stomach?
H2 receptors.
Name a key H2-receptor antagonist that replaced Ranitidine.
Famotidine.
Is the inhibition of proton pumps by Omeprazole and Lansoprazole reversible or irreversible?
Irreversible.
What happens to the activity of Omeprazole and Lansoprazole at a neutral pH?
They become inactive.
Why do Omeprazole and Lansoprazole accumulate in the secretory canaliculi of parietal cells?
They are weak bases which are activated in an acidic environment.
What is a prodrug?
A biologically inactive compound which can be metabolised in the body to produce a drug.
How do Omeprazole and Lansoprazole enter the parietal cells?
From the circulation via the basolateral membrane.
What is GORD?
When the liquid content of the stomach regurgitates into the oesophagus.
What is reflux oesophagitis?
Inflammation of the lower oesophagus produced by persistent episodes of reflux.
What are some symptoms of reflux oesophagitis?
Heartburn
Regurgitation of food into the mouth
Haematemesis
What is haematemesis?
Vomiting blood.
List 3 complications of reflux oesophagitis.
- Oesophageal ulceration
- Peptic stricture
- Barrett’s oesophagus
What is a peptic stricture? What can it cause difficulties with?
A narrowing or tightening of the oesophagus that causes swallowing difficulties.
What is Barrett’s oesophagus?
Barrett’s oesophagus is a condition in which tissue that is similar to the lining of your intestine replaces the tissue lining your oesophagus via a process called intestinal metaplasia.
List 3 common causes of peptic ulcers.
- NSAIDs
- Zollinger-Ellison Syndrome
- H. Pylori infection
NSAIDs impair renewal of the gastric mucosal barrier by interfering with the production of what?
Prostaglandins.
What 4 things do prostaglandins E2 and I2 do to support renewal of the gastric mucosal barrier?
- Stimulating gastric mucus production
- Stimulating bicarbonate secretion
- Inhibiting gastric acid production
- Promoting local healing
Which enzyme do NSAIDs inhibit? What does this enzyme do?
Cyclo-oxygenase. It catalyzes the first step in the synthesis of prostaglandins from arachidonic acid.
If a patient is taking NSAIDs but is at an increased risk of GI-adverse effects, what should be co-prescribed?
Proton pump inhibitor (omeprazole or lansoprazole).
What is Zollinger-Ellison syndrome?
A condition in which a gastrin-secreting tumour or hyperplasia of the islet cells in the pancreas causes overproduction of gastric acid, resulting in recurrent peptic ulcers.
What shape is H. Pylori and is it Gram-positive or negative?
Spiral shaped and Gram-negative.
What enzyme does H. Pylori release? This breaks down what into what?
Urease, which breaks down urea into CO2 and NH3 (ammonia).
How does NH3 affect gastric acid?
It neutralises it.
What is the standard treatment of a H. Pylori infection?
Antibiotics and a proton pump inhibitor.
What are the medical terms for an absence and a deficiency of hydrochloric acid in the gastric juice?
Achlorhydria/ Hypochlorhydria.
What are some consequences of achlorhydria and hypochlorhydria?
- Impaired ability to digest and absorb certain nutrients.
2. Increased vulnerability of GI tract to bacterial infection.
