BMA Concise Guide to Medicine & Drugs


Brand names [dressings] Algisite M, Algosteril, Kaltostat, Melgisorb, SeaSorb, Sorbalgon, Sorbsan; [oral] Gaviscon Infant

Used in the following combined preparations Acidex, Gastrocote, Gaviscon, Peptac, Rennie Duo, Topal


Drug group Antacid

Overdose danger rating Low

Dependence rating Low

Prescription needed No

Available as generic Yes


“Alginates” is a group term that refers to a mixture of compounds extracted from brown algae (seaweeds). When the powder extract is mixed with water, alginates become a thick viscous fluid or gel depending on the chemicals used. Alginates combined with antacids form a “raft” that floats on the surface of the stomach contents, which reduces reflux and protects the lining of the oesophagus from attack by acid regurgitated from the stomach. Many of these combined preparations of alginates are used to treat mild gastro-oesophageal reflux disease. A number of indigestion remedies on sale to the public also contain alginates.

The properties of alginates are also used in wound dressings where, in the form of a woven pad, they absorb fluids from the surface of the wound, keeping it moist and allowing it to heal.


Follow instructions on the label. Call your doctor if symptoms worsen.

How taken/used Chewable tablets, liquid, powder.

Frequency and timing of doses 4 x daily after meals and at bedtime.

Adult dosage range 800–2,000mg daily.

Onset of effect 10–20 minutes.

Duration of action 3–4 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember, if you need it.

Stopping the drug Alginates can be safely stopped as soon as you no longer need them.

Exceeding the dose Overdose of alginates is likely to produce abdominal distension, without any other symptoms. Notify your doctor if symptoms are severe.


The antacid salts used in combined oral preparations of alginates may cause abdominal discomfort and distension, and, rarely, nausea. Discuss with your doctor if any of these symptoms are severe.




Be sure to consult your doctor or pharmacist before taking this drug if:

· You are on a salt-restricted diet.

· You are taking other medicines.

Pregnancy No evidence of risk to developing baby. Some products can be used for heartburn in pregnancy.

Breast-feeding No evidence of risk.

Infants and children Reduced dose necessary.

Over 60 No special problems.

Driving and hazardous work No known problems.

Alcohol No known problems.


No problems expected.