medicinal chemistry of GI and GORD drugs

Term 1

Properties of antacids

• alkaline inorganic salts

  • Carbonate salts of magnesium or calcium

  • Bicarbonate salts of potassium or sodium

  • Hydroxides of magnesium or aluminium

Limitations of antacids:

• regular use = constipation, diarrhoea or discomfort

  • Accumulation of CO2

• Prolonged use = affect blood pH, systemic absorption of mental ions

• Do not reduce acid secretion neutralises

• CaCO3 (antacid) promotes acid secretion

How do antacids break the integrity of enteric coatings:

Antacids increase the pH of the GI tract

Enteric coatings only dissolve at a high pH (small intestine)

• breaks down prematurely not at the site

Histamine promotes acid secretion…

Through activation of parietal cell H2 receptors

How do PPIs work:

• covalently modifies amino acid sequence of proton pump

• Leads to inactivation

How does loperamide work?

• acts on u-opioid receptors on the myenteric plexus

• Reduces smooth muscle tone and decreases contraction