hepatic
impairment
Antacids (usually containing aluminium or magnesium compounds) can often
relieve symptoms in
ulcer dyspepsia and in
non-erosive
gastro-oesophageal reflux (see also
section 1.1); they are also sometimes used in functional
(non-ulcer) dyspepsia but the evidence of benefit is uncertain. Antacids are
best given when symptoms occur or are expected, usually between meals and at
bedtime, 4 or more times daily; additional doses may be required up to once an
hour. Conventional doses e.g. 10
mL 3 or 4
times daily of liquid magnesium–aluminium antacids promote ulcer healing, but
less well than antisecretory drugs (
section 1.3); proof of a relationship between healing and
neutralising capacity is lacking. Liquid preparations are more effective than
tablet preparations.
Aluminium- and
magnesium-containing antacids (e.g. aluminium
hydroxide, and magnesium carbonate, hydroxide and trisilicate), being relatively
insoluble in water, are long-acting if retained in the stomach. They are
suitable for most antacid purposes.
Magnesium-containing antacids tend to be laxative
whereas
aluminium-containing antacids may be
constipating; antacids containing both magnesium and aluminium may reduce these
colonic side-effects. Aluminium accumulation does not appear to be a risk if
renal function is normal (see also
Appendix 3).
The acid-neutralising capacity of preparations that contain more than one
antacid may be the same as simpler preparations. Complexes such as
hydrotalcite confer no special advantage.
Sodium bicarbonate should no longer be prescribed alone for the relief
of dyspepsia but it is present as an ingredient in many indigestion remedies.
However, it retains a place in the management of urinary-tract disorders (
section
7.4.3) and acidosis (
section 9.2.1.3 and
section 9.2.2). Sodium bicarbonate should be avoided in
patients on salt-restricted diets.
Bismuth-containing antacids (unless chelates) are not recommended
because absorbed bismuth can be neurotoxic, causing encephalopathy; they tend to
be constipating.
Calcium-containing antacids
(section 1.1.2) can induce rebound acid secretion: with
modest doses the clinical significance is doubtful, but prolonged high doses
also cause hypercalcaemia and alkalosis, and can precipitate the milk-alkali
syndrome.
Simeticone (activated dimeticone) is added
to an antacid as an antifoaming agent to relieve flatulence. These preparations
may be useful for the relief of hiccup in palliative care.
Alginates,
added as protectants, may be useful in gastro-oesophageal reflux disease (
section 1.1 and
section 1.1.2). The amount of additional ingredient or
antacid in individual preparations varies widely, as does their sodium content,
so that preparations may not be freely interchangeable.
See also
section
1.3 for drugs used in the treatment of peptic ulceration.
Interactions
Antacids should preferably not be taken at the same time as other drugs since
they may impair absorption. Antacids may also damage enteric coatings designed
to prevent dissolution in the stomach. See also
Appendix 1 (antacids,
calcium salts).
Low Na+
The words low Na+ added after some preparations indicate a sodium
content of less than 1 mmol per tablet or
10-mL dose.
