Symptoms in the Pharmacy :Gastrointestinal Tract Problems(7)

indigestion

When to refer

• Age over 45 if symptoms develop for first time
• Symptoms are persistent (longer than 5 days) or recurrent
• Pain is severe
• Blood in vomit or stools
  
• Pain worsens on effort
• Persistent vomiting
• Treatment has failed
• Adverse drug reaction is suspected
• Associated weight loss
• Children

Treatment timescale
If symptoms have not improved within 5 days, the patient should see
the doctor.

Management
Once the pharmacist has excluded serious disease, treatment of dyspepsia
with antacids or an H2 antagonist may be recommended and is
likely to be effective. The preparation should be selected on the basis
of the individual patient’s symptoms. Smoking, alcohol and fatty
meals can all aggravate symptoms, so the pharmacist can advise
appropriately.

Antacids
In general, liquids are more effective antacids than are solids; they are
easier to take, work quicker and have a greater neutralising capacity.
Their small particle size allows a large surface area to be in contact
with the gastric contents. Some patients find tablets more convenient
and these should be well chewed before swallowing for the best effect.
It might be appropriate for the patient to have both; the liquid could
be taken before and after working hours while the tablets could be
taken during the day for convenience. Antacids are best taken about
1 h after a meal because the rate of gastric emptying has then slowed
and the antacid will therefore remain in the stomach for longer. Taken
at this time, antacids may act for up to 3 h compared with only
30 min–1 h if taken before meals.

Sodium bicarbonate
Sodium bicarbonate is the only absorbable antacid that is useful in
practice. It is water-soluble, acts quickly, is an effective neutraliser of
acid and has a short duration of action. It is often included in OTC
formulations in order to give a fast-acting effect, in combination with
longer-acting agents. However, antacids containing sodium bicarbonate
should be avoided in patients if sodium intake should be restricted
(e.g. in patients with congestive heart failure). Sodium bicarbonate
increases excretion of lithium leading to reduced plasma levels. The
contents of OTC products should therefore be carefully scrutinised
and pharmacists should be aware of the constituents of some of the
traditional formulary preparations. For example, magnesium trisilicate
mixture contains sodium bicarbonate and is therefore relatively
high in sodium. The relative sodium contents of different antacids can
be found in the BNF. In addition, long-term use of sodium bicarbonate
may lead to systemic alkalosis and renal damage. In short-term use,
however, it can be a valuable and effective antacid. Its use is more
appropriate in acute rather than chronic dyspepsia.

Aluminium and magnesium salts (e.g. aluminium hydroxide, magnesium
trisilicate)
Aluminium-based antacids are effective; they tend to be constipating
and this can be a useful effect in patients if there is slight diarrhoea.
Conversely, the use of aluminium antacids is best avoided in anyone
who is constipated and in elderly patients, who have a tendency to be
so. Magnesium salts are more potent acid neutralisers than aluminium.
They tend to cause osmotic diarrhoea as a result of the formation
of insoluble magnesium salts and are therefore useful in patients who
are slightly constipated. Combination products containing aluminium
and magnesium salts cause minimum bowel disturbance and are
therefore valuable preparations for recommendation by the pharmacist.

Calcium carbonate
Calcium carbonate is commonly included in OTC formulations. It
acts quickly, has a prolonged action and is a potent neutraliser of
acid. It can cause acid rebound and, if taken over long periods at
high doses, can cause hypercalcaemia and so should not be recommended
for long-term use. Calcium carbonate and sodium bicarbonate
can, if taken in large quantities with a high intake of milk, result in
the milk–alkali syndrome. This involves hypercalcaemia, metabolic
alkalosis and renal insufficiency; its symptoms are nausea, vomiting,
anorexia, headache and mental confusion.

Dimeticone (dimethicone)
Dimeticone is sometimes added to antacid formulations for its
defoaming properties. Theoretically, it reduces surface tension and
allows easier elimination of gas from the gut by passing flatus or
eructation (belching). Evidence of benefit is uncertain.

Interactions with antacids
Because they raise the gastric pH, antacids can interfere with enteric
coatings on tablets that are intended to release their contents further
along the GI tract. The consequences of this may be that release of the
drug is unpredictable; adverse effects may occur if the drug is in
contact with the stomach. Alternatively, enteric coatings are sometimes
used to protect a drug that may be inactivated by the low pH in
the stomach; so concurrent administration of antacids may result in
such inactivation.

Sucralfate works best in an acid medium; so concurrent administration
with antacids should be avoided. Excretion of quinidine may
be reduced and plasma levels increased if the urine is alkaline and
antacids may increase urinary pH.
Antacids may reduce the absorption of tetracyclines, azithromycin,
itraconazole, ketoconazole, penicillamine, chlorpromazine, diflunisal,
dipyridamole, ciprofloxacin, norfloxacin, ofloxacin, rifampicin and
zalcitabine. Sodium bicarbonate may increase the excretion of lithium
and lower the plasma level, so that a reduction in lithium’s therapeutic
effect may occur. Antacids containing sodium bicarbonate should not
therefore be recommended for any patient on lithium therapy.
The changes in pH that occur after antacid administration can
result in a decrease in iron absorption if iron is taken at the same
time. The effect is caused by the formation of insoluble iron salts due
to the changed pH. Taking iron and antacids at different times should
prevent the problem. See BNF for a detailed listing of interactions
with antacids.

Cimetidine, famotidine and ranitidine
Cimetidine, famotidine and ranitidine have been deregulated from
prescription-only status for the short-term treatment of dyspepsia
and heartburn . Cimetidine affects the cytochrome
P450 enzyme system in the liver and therefore produces a range of
drug interactions ; famotidine and ranitidine do not affect
the cytochrome P450 system. Treatment with these drugs is limited to
a maximum of 2 weeks.
Discussing the use of H2 antagonists with local family doctors
would be valuable. Perhaps agreeing general guidelines or a protocol
for their use could be a feature of the discussion.

Domperidone
Domperidone 10 mg can be used for the treatment of postprandial
stomach symptoms of excessive fullness, nausea, epigastric bloating
and belching, occasionally accompanied by epigastric discomfort and
heartburn. It increases the rate of gastric emptying and transit time in
the small intestine, and also increases the strength of contraction of
the oesophageal sphincter. Domperidone can be used in patients aged
16 and over. The maximum dose is 10mg and the maximum daily
dose 40 mg. When used as a POM medicine, domperidone is used to
treat nausea and vomiting, but these indications are not included in
the P licence and patients with these symptoms would need to be
referred.