Alginic acid

Identification

Generic Name

Alginic acid

DrugBank Accession Number

DB13518

Background

Alginic acid, also referred to as algin or alginate, is a hydrophilic or anionic polysaccharide isolated from certain brown seaweed (Phacophycae) via alkaline extraction. It is present in cell walls of brown algae where it forms a viscous gel when binding with water. Alginic acid is a linear polymer consisted of L-glucuronic acid and D-mannuronic acid residues connected via 1,4-glycosidic linkages ⁴. Available in different types of salt, alginic acid has been used in a variety of uses in food, cosmetics and pharmaceu-tical products for over 100 years ⁴. Alginic acid is an FDA-approved food ingredient in soup and soup mixes as an emulsifier, thickener, and stabilizer ⁵. It is also available in oral dietary supplements and is found in antacids such as Gaviscon to inhibit gastroesophageal reflux by creating a physical barrier in presence of gastric acid ⁹. Alginate-based raft-forming formulations in the management of heartburn and gastric acid reflux have been used worldwide for over 30 years ⁴.

Type

Small Molecule

Groups

Approved, Investigational

Synonyms

(Alginate)n
(Alginate)n+1
algin
alginate
Alginic acid
Norgine

External IDs

A 2830-9
E-400
INS NO.400
INS-400

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Pharmacology

Indication

Indicated for the management of gastric reflux, reflux oesophagitis, hiatus hernia, heartburn (including heartburn of pregnancy) and similar gastric distress ⁹.

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Associated Conditions

Indication Type	Indication	Combined Product Details	Approval Level	Dose Form
Used in combination to treat	Acid reflux	Combination Product in combination with: Calcium carbonate (DB06724), Aluminum hydroxide (DB06723)	••• •••	••••••••••
Used in combination for symptomatic treatment of	Acid reflux	Combination Product in combination with: Simethicone (DB09512)	••••••••••••	••••••••••
Used in combination to treat	Dyspepsia	Combination Product in combination with: Calcium carbonate (DB06724), Aluminum hydroxide (DB06723)	••• •••	••••••••••
Used in combination for symptomatic treatment of	Dyspepsia	Combination Product in combination with: Potassium bicarbonate (DB11098)	••••••••••••	••••••• ••••••••
Used in combination for symptomatic treatment of	Flatulence	Combination Product in combination with: Simethicone (DB09512)	••••••••••••	••••••••••

Contraindications & Blackbox Warnings

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Pharmacodynamics

Alginic acid reduces reflux via its floating, foaming, and viscous properties ². Alginic acid precipitates upon contact with gastric acid to create a mechanical barrier, or a "raft", that displaces the postprandial acid pocket ³. The formation of a raft is thought to occur rapidly, often within a few seconds of dosing ⁴. In clinical trials, alginic acid was effective in reducing the symptoms of gastroesophageal reflux disease (GERD) ³. In healthy volunteers, alginic acid in combination with an antacid was effective in decreasing postprandial reflux in the upright position ¹. Alginic acid is able to bind to cations when ingested ⁶.

Mechanism of action

Once orally administered, alginic acid reacts with gastric acid to form a floating "raft" of alginic acid gel on the gastric acid pool. Alginate-based raft-forming formulations commonly contain sodium or bicarbonate; bicarbonate ions are converted to carbon dioxide in presence of gastric acid and get 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 ⁴. The "raft" has a near neutral pH due to carbon dioxide and floats on the stomach contents and potentially functions as a barrier to impede gastroesophageal reflux ^1,9. In severe cases, the raft itself may be refluxed into the oesophagus in preference to the stomach contents and exert a demulcent effect ⁹.

Absorption

The absorption into the systemic circulation from oral formulations of alginic acid is reported to be minimal, as the mode of action of alginic acid is physical ⁹.

Volume of distribution