Review article: alginate-raft formulations in the treatment of heartburn
and acid reflux
Authors
Mandel KG. Daggy BP. Brodie DA. Jacoby HI.
Source
Alimentary Pharmacology & Therapeutics. 14(6):669-90, 2000 Jun.
Abstract
Alginate-based raft-forming formulations have been marketed word-wide for over
30 years under various brand names, including Gaviscon. They
are used for the symptomatic treatment of heartburn and oesophagitis, and appear
to act by a unique mechanism which differs from that of traditional antacids.
In the presence of gastric acid, alginates precipitate, forming a gel.
Alginate-based raft-forming formulations usually contain sodium or potassium
bicarbonate; in the presence of gastric acid, the bicarbonate is converted to
carbon dioxide which becomes entrapped within the gel precipitate, converting
it into a foam which floats on the surface of the gastric contents, much like
a raft on water.
Both in vitro and in vivo studies have demonstrated that alginate-based rafts
can entrap carbon dioxide, as well as antacid components contained in some formulations,
thus providing a relatively pH-neutral barrier.
Several studies have demonstrated that the alginate raft can preferentially
move into the oesophagus in place, or ahead, of acidic gastric contents during
episodes of gastro-oesophageal reflux; some studies further suggest that the
raft can act as a physical barrier to reduce reflux episodes. Although some alginate-based
formulations also contain antacid components which can provide significant acid
neutralization capacity, the efficacy of these formulations to reduce heartburn
symptoms does not appear to be totally dependent on the neutralization of bulk
gastric contents. .
The strength of the alginate raft is dependant on several factors, including
the amount of carbon dioxide generated and entrapped in the raft, the molecular
properties of the alginate, and the presence of aluminium or calcium in the antacid
components of the formulation. Raft formation occurs rapidly, often within a
few seconds of dosing; hence alginate-containing antacids are comparable to traditional
antacids for speed of onset of relief. .
Since the raft can be retained in the stomach for several hours, alginate-based
raft-forming formulations can additionally provide longer-lasting relief than
that of traditional antacids. .
Indeed, clinical studies have shown Gaviscon is superior
to placebo, and equal to or significantly better than traditional antacids for
relieving heartburn symptoms. Alginate-based, raft-forming formulations have
been used to treat reflux symptoms in infants and children, and in the management
of heartburn and reflux during pregnancy.
While Gaviscon is effective when used alone, it is compatible
with, and does not interfere with the activity of antisecretory agents such as
cimetidine. Even with the introduction of new antisecretory and promotility agents,
alginate-rafting formulations will continue to have a role in the treatment of
heartburn and reflux symptoms.
Their unique non-systemic mechanism of action provides rapid and long-duration
relief of heartburn and acid reflux symptoms. |
