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Dyspepsia - unidentified cause - Management
What issues should I consider when prescribing an antacid or alginate?
- Antacids work by neutralizing gastric acid. However, the effect is only for a relatively short period, requiring frequent administration [Maton and Burton, 1999].
- Alginates are added to antacid preparations to relieve reflux symptoms by forming a floating viscous raft on top of the gastric contents, thus providing a physical barrier to reflux.
- Administration:
- Antacids are best given when symptoms occur or are expected, that is after meals and at bedtime. They also remain in the stomach for longer at these times, and therefore have longer to act. They have a duration of action of up to 3 hours when given with or 1 hour after a meal. When ingested on an empty stomach, the duration of action is reduced to 20 to 60 minutes [Maton and Burton, 1999].
- For maximum benefits, alginate preparations should be taken after meals, otherwise the alginate rapidly exits the stomach; this provides only transient relief of symptoms courtesy of the antacid component [de Caestecker, 2001].
- Choice of preparations:
- A variety of antacids, with or without alginates, are available on prescription and for sale over-the-counter.
- There is limited evidence on the efficacy of antacids in the management of dyspepsia [Maton and Burton, 1999; de Caestecker, 2001]. The evidence for antacids in relieving dyspeptic symptoms is poor.
- Antacids containing combinations of aluminium salts with magnesium salts may be preferable to magnesium salts alone (which may cause diarrhoea) or aluminium salts alone (which may cause constipation) [BNF 55, 2008].
- Compound alginate preparations are useful for people with mild reflux symptoms. Evidence from a systematic review found alginates to be more effective than placebo in relieving symptoms of gastro-oesophageal reflux.
- Antacids containing sodium bicarbonate should be avoided in those on salt-restricted diets.
- Antacids containing only calcium salts are less preferred due to concerns that they might induce acid rebound (although the clinical significance is uncertain at low doses) [BNF 55, 2008].
- Formulation:
- Liquid antacid preparations may be more effective than tablet preparations [BNF 55, 2008] although CKS found no evidence to support this.
- Drug interactions:
- All antacids can produce drug interactions by changing gastric pH, thus affecting drug absorption.
- This can be avoided by taking antacids at different times to other drugs.
- Adverse effects:
- Most adverse effects are minor, if antacids are used only periodically and in small amounts.
- However, when large doses are taken for long periods of time, significant adverse effects may occur especially in those with underlying diseases such as chronic renal failure (avoid aluminium-containing antacids in this group) [Maton and Burton, 1999]. Prolonged high doses of calcium-containing antacids can cause hypercalcaemia and alkalosis, and precipitate milk-alkali syndrome [BNF 55, 2008].
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