ANTACIDS
Human Stomach
 Gastric juices in stomach
 Contain HCl (aq)
 Ph 1-3
 To suppress growth of
bacteria
 To help in digestion by
hydrolysing proteins to
amino acids
Indigestion
 Excess acid production
 Abdominal discomfort
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after eating
Over eating
Stress
Certain foods
Acid eats away protective
mucus layer
Painful ulcers
Antacids
 Remedy for excess

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
stomach acidity
Bases
Metal oxides, hydroxides
Metal carbonates
Metal
hydrogencarbonates
(bicarbonates)
Effect of Antacids
 Neutralise excess acid
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and adjust stomach ph to
desired level
Stomach lining repairs
itself
Active ingredients
Aluminium hydroxide
Magnesium hydroxide
Sodium hydrogen
carbonate
Alginates
 Combined with antacids
 Extracted from brown
seaweeds
 Produce a neutralising
layer rthat prevents acid
reflux
 E.g. they prevent acid
from rising into
oesophagus
 «Heartburn»
Dimethicone
 Anti-foaming agent
 Added to reduce surface
tension of gas bubbles
 Causes bubbles to
coalesce (come together)
 Produces defoaming
action
Side effects
 Aluminium hydroxide
may cause constipation
 Can prevent uptake of
phosphate ions
(precipitation of
aluminium phosphate)
 Large charge to size
density leads to binding
with other drugs
Side Effects
 Magnesium hydroxide
has laxative properties
 Calcium carbonate may
lead to kidney stones
 Sodium ions may lead to
hypertension
Alkalosis
 Taking too much antacid
leads to alkalosis (a rise
in ph of blood)
 Also can lead to excessive
amounts of calcium ions
in body
Question
 Two solid antacid products contain same mass of
different active ingredients. One contains sodium
bicarbonate, the other calcium carbonate. Which is
the better buy and why ?
To Do
 Look at active ingredients of antacids on page 410
 Also look at chemical equations
 Then try question 3 on page 434