Antacids and Simeticone and Other Indigestion Remedies

Dyspepsia and heartburn are very common amongst the adult population and most do not seek medical help but self-manage with over-the-counter (OTC) preparations. These are frequently heavily marketed direct-to-patient. Often by the time someone consults, they will have tried a variety of indigestion remedies. They include:

• Antacids which are gastric acid-neutralizing or adsorbing medications, used to relieve symptoms of dyspepsia or heartburn. They usually contain aluminium and/or magnesium salts (eg aluminium hydroxide, magnesium carbonate, hydroxide or trisilicate) as these compounds are relatively insoluble and longer-acting.
• Alginates form a raft that floats on the surface of the stomach contents and provide a physical barrier to gastro-oesophageal reflux. Frequently, these are found in preparations combined with an antacid eg Acidex®, Gastrocote®, Rennie Duo®.
• Simeticone is frequently added to antacids as an anti-foaming agent to relieve wind eg Asilone®, Maalox Plus®. It also has a role in the palliative treatment of hiccups. It is licensed and widely used for the treatment of infant colic (Dentinox®, Infacol®) but evidence shows limited benefit.¹

Symptomatic relief of dyspepsia and heartburn

• The clinical efficacy of antacids and alginates has been questioned: placebo response can be large and only small to negligible added benefit of antacids is suggested by meta-analysis.^2,3 RCT evidence shows short-term (after 4-8 weeks) symptom reduction with antacids compared to placebo, but no significant difference in endoscopic healing. Compared to ranitidine, antacids are less effective at reducing heartburn after 12 weeks' treatment.⁴
• Epidemiological studies, however, suggest that they are effective self-treatment in the large section of the population not seeking medical help to control symptoms. An American study in the 1980s showed that a quarter of the US apparently-healthy adult population (ie those not seeking medical help with symptoms) used at least 2 doses of antacid a month and that when heavy ( >6 doses/week) long-term users underwent endoscopy, there was evidence of GORD in the majority, suggesting that antacids were providing symptomatic relief.⁵
• Current NICE guidelines⁶ for the management of dyspepsia suggest:
  • Self-treatment with antacids and/or alginates is appropriate for symptom relief
  • Additional medication such as H2 receptor antagonists (H2RAs) or proton pump inhibitors (PPIs) should be considered where symptoms are persistently reducing an individual's quality of life
  • Medication should be combined with lifestyle advice (healthy eating, weight reduction, smoking cessation) and the avoidance of precipitants (alcohol, coffee, chocolate, fatty foods) which can trigger attacks. Simple behavioural changes such as raising the bed head and eating well in advance of bed time may also be effective.

Gastro-oesophageal reflux in infants

Gastro-oesophageal reflux disease (GORD) is common in infancy due to functional immaturity of the lower oesophageal sphincter.⁷ Carers describe large regurgitations or regular vomiting. It usually resolves spontaneously by 12-18 months.
Serious reflux is uncommon but can cause potentially serious complications such as failure to thrive, feeding difficulties, pulmonary aspiration, strictures secondary to oesophagitis, apnoeas in preterm infants.
Babies with mild, uncomplicated reflux can usually be diagnosed clinically and treated without further investigation. Treatment includes:

• Reassuring parents that the condition is self-limiting and benign
• Advising parents to feed child propped up
• Keep baby in the left lateral position after feeds
• Add carob-based thickening agents to feeds
• Use of an alginate - Infant Gaviscon® reduces average reflux height but it is unlikely that clinical benefit is related to any anti-reflux mechanism, rather placebo or protective oesophageal coating.⁸Note, the adult formulation of Gaviscon® contains sodium bicarbonate and should not be given to children under 6 years as they may have difficulty excreting the sodium. Infant Gaviscon® contains less sodium (0.92 mmol Na /dose) but still is not suitable for pre-term infants or those at risk of excessive water loss.⁹
• Magnesium-containing antacids are sometimes used for the short-term relief of intermittent symptoms of GORD - aluminium-containing antacids are usually avoided in infants because accumulation may lead to elevated plasma aluminium concentrations and rarely antacid-induced rickets.¹⁰

Where history is not typical or where complications exist or where the above measures have failed, referral to paediatrics for 24 hour oesophageal PH monitoring and other investigations is sensible. Secondary care treatments may include an H2RA or omeprazole.

Gastro-oesophageal reflux in pregnancy

GORD is also common in pregnancy due to progesterone-related relaxation of the lower oesophageal sphincter and external pressure from the enlarging uterus.¹¹

• Lifestyle modifications should be used first line.
• Antacids or alginates are prescribed where these fail to control symptoms adequately. Used in appropriate doses, these drugs are considered safe in pregnancy although some consider they could be a potential factor (among many potential candidate foods and drugs taken by women in pregnancy and during lactation) in the development of food allergy in children.¹² One UK survey showed that 23% pregnant women had used antacids by 32 weeks gestation.¹³ If these drugs are inadequate consider ranitidine or omeprazole.¹¹
• A case for offering low sodium products to women with gestational hypertension or pre-eclampsia has been made but there is insufficient trial data to support or refute it.¹¹

• Diarrhoea and Constipation - magnesium-containing antacids tend to be laxative, whilst aluminium-containing antacids are constipating - combination products are least likely to alter bowel habit.
• Sodium bicarbonate is very well absorbed and causes alkalosis in high doses (the so-called “milk alkali syndrome”¹⁴). This is much rarer today as sodium bicarbonate is avoided as an antacid and aluminium and magnesium salts are much less readily absorbed and consequently safer.
• Some antacids and alginates have high sodium content and should be avoided by those on a low sodium diet. Preparations labelled “low sodium” indicates a sodium content of less than 1 mmol per tablet or 10 ml dose.
• Care should be taken prescribing antacids containing calcium carbonate to patients with hypercalcaemia, nephrocalcinosis and recurrent calcium containing renal calculi.
• Giving alginates to infants, particularly breast-fed babies, can be challenging. Usual prescribing practice is to give 1-2 sachets (depending on weight) Gaviscon Infant® with each feed up to six times per day. The powder can be mixed with a small amount of fluid (either cooled boiled water, formula or expressed breast milk) and given, ideally pre-feed, by spoon, syringe or bottle. An important side-effect to mention to parents is constipation.
• Antacids and alginates can impair iron absorption so advise that they should not be taken within 2 hours of iron supplements. This is particularly important in pregnant women.
• Antacids are best taken at the times when symptoms occur (usually after meals and at bedtime) and can be used prn.

Always check if a patient is using antacids since these are such commonly used OTC drugs with potential to interact with many prescribed drugs:

• Avoid taking antacids at the same time as other drugs since they may impair absorption. Many common drugs' absorption is decreased including some antibiotics, antiepileptics, antimalarials, digoxin, lansoprazole and antivirals.
• In particular, an alkaline environment can cause the precipitation of tetracycline antibiotics.