Alginates work mechanically rather than chemically. They form a gel raft that floats on top of the stomach contents and physically blocks acid from rising into the gullet — which is why they suit reflux that comes on lying down, and why they are usually the first suggestion for heartburn in pregnancy.
A plain antacid neutralises acid that is already there. It works within minutes and wears off within an hour or two.
An alginate does that too — most products combine both — but adds the raft, which lasts longer and works against the reflux itself rather than just the acidity. If your heartburn is worst at night or when you bend over, an alginate is usually the better choice.
Take after meals and at bedtime — that is when the raft is most useful, because there is stomach content for it to float on. Taking one on an empty stomach makes far less sense.
Chewable tablets should be chewed thoroughly, not swallowed whole. Liquids are shaken before use.
Leave a two-hour gap between an antacid or alginate and other medicines. They can reduce the absorption of several, including some antibiotics, thyroid medicine and iron tablets.
Most products contain sodium, so check with us if you are on a low-sodium diet, have heart failure, or have kidney problems. Some contain calcium or potassium, which matters for a few people.
They are generally considered suitable in pregnancy and while breastfeeding, and are usually the first medicine tried for pregnancy heartburn after dietary and posture measures.
If you need one most days for more than a couple of weeks, that is worth a conversation — a longer-acting treatment or an investigation may be more appropriate than indefinite antacid use.
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