The effect of Gaviscon on acid reflux episodes and on the position of the gastric acid pocket: A Scintigraphic study

Gastro-esophageal reflux is a physiological phenomenon in which gastric
contents flow back into the esophagus. When reflux causes symptoms and/ or
esophageal damage, it is referred to as gastro esophageal reflux disease
(GERD), which is a very common chronic condition.(1)
Most reflux episodes occur after a meal, when the stomach is filled with
recently ingested food. Until recently, it was thought that gastric contents
mix well after a meal. However, almost immediately after a meal highly acidic
reflux episodes occur. Fletcher et al have shown that in the proximal stomach
an unbuffered pool of acid floats on top of the ingested food, which explains
the acidic reflux immediately after a meal while the majority of the gastric
contents are not acidic.(2) This unbuffered pool of acid is referred to as the
gastric acid pocket. Recently, our lab has shown that the position of the acid
pocket relative to the crural diaphragm mainly determines the acidity of the
refluxate.(3) In patients with GERD, the fluid of the gastric acid pocket is
located above or at the level of the diaphragm, and is as such the most
important source of the refluxate.
Apart from an explanation for acid reflux episodes in GERD, the acid pocket
also represents a unique therapeutic target.(4) Specifically, alginates, based
on the concept of forming a gel-like barrier on top of gastric content, may
displace or eliminate the *acid pocket*. (5) Alginates are natural
polysaccharide polymers isolated from brown seaweed (Phacophycae). On contact
with gastric acid, alginate precipitates into a low density viscous gel of near
neutral pH in a matter of seconds in vitro or a few minutes in vivo. (6;7) With
the pH change, the sodium bicarbonate contained in the alginate-antacid
formulation releases carbon dioxide, which is then trapped in the alginate gel
causing it to float to the top of the gastric contents like a *raft*. (6;7)
Hence, alginate-based formulations with sodium bicarbonate may effect direct
and immediate neutralisation of the acid pocket. The duration of in vivo action
likely varies, but the raft of the original alginate based formulation
(Gaviscon), remains in the stomach for up to 4 h and is retained on top of the
meal. (7)

Earlier studies suggest that Gaviscon alters the position of the acid pocket,
as the number of acid reflux episodes decreased but the number of nonacid
reflux events almost doubled after drug intake. (8) However, until now the
formation of the raft in relation to the acid pocket has never been visualized
in vivo. Therefore, we aim to perform a study to visualize the alginate raft
formation and to assess the effect of alginates-antacid formulations on reflux
parameters and the position of the acid pocket.

A randomized controlled study, comparing Gaviscon liquid to antacid suspension.

Oral administration of 10 mL Gaviscon

Risk of participation in the study is limited. Radiation exposure and the
introduction of the manometry catheter are the main risks and burden of the
study.

Radiation
During two study day 350 MBq 99mTc-pertechnetate is applied intravenously.
99mTc-pertechnetate has no known side effects other then the radiation.
Additionally gaviscon is labelled with 1 MBq of 113m-Indium. The radiation dose
is in the intermediate category. Patients who recently participated in a study
with radiation are excluded from the trial.

Group relatedness and benefit.
The patients studied all have proven GERD. Patients do not benefit from
participation in the study.