What conditions are they used to treat?
H2 blockers are commonly used:
- To reduce acid
reflux which may cause heartburn or oesophagitis (inflammation of the
gullet). These conditions are sometimes called gastro-oesophageal
reflux disease or GORD.
- To treat ulcers in the stomach and duodenum (part of the gut).
- To help heal ulcers associated with anti-inflammatory drugs called NSAIDS (non-steroidal anti-inflammatory drugs).
- In other conditions where it is helpful to reduce acid in the stomach.
They have also been used as one part of a treatment to get rid of Helicobacter pylori,
a bacterium (germ) found in the stomach which can cause ulcers.
However, another class of drugs, called Proton Pump Inhibitors, are now
generally preferred for this use.
How do H2 blockers work?
Your stomach
normally produces acid to help with the digestion of food and to kill
bacteria. This acid is corrosive so your body produces a natural mucus
barrier which protects the lining of the stomach from being eroded.
In
some people this barrier may have broken down allowing the acid to
damage the stomach, causing an ulcer. In others there may be a problem
with the muscular band at the top of the stomach (the sphincter) that
keeps the stomach tightly closed. This may allow the acid to escape and
irritate the oesophagus (gullet). This is called ‘acid reflux’ which
can cause heartburn and/or oesophagitis.
The letter H in their
name stands for histamine. Histamine is a chemical naturally produced
by certain cells in the body including cells in the lining of the
stomach called the enterochromaffin-like cells (ECL cells). Histamine
released from ECL cells then stimulate the acid making cells (parietal
cells) in the lining of the stomach to release acid. What H2 blockers
do is stop the acid making cells in the stomach lining from responding
to histamine. This reduces the amount of acid produced by your stomach.
By decreasing the amount of acid, H2 blockers can help to
reduce acid reflux related symptoms such as heartburn. This can also
help to heal ulcers found in the stomach or duodenum.
Note: H2
blockers are a different class of drugs to ‘antihistamine drugs’ which
block H1 receptors in cells that are involved in allergy reactions.
Also, H2 blockers are more correctly called ‘histamine H2 receptor
antagonists’ – but they are commonly just called H2 blockers.
Can I buy H2 blockers or do I need a prescription?
You
can buy some of these drugs over the counter at pharmacies. They are
commonly marketed as drugs for ‘relief of heartburn, indigestion, acid
indigestion and excess stomach acid’ – or similar . However, if you
need to use an H2 blocker regularly for more than two weeks you should
consult your doctor.
How do I take H2 blockers?
Your doctor or
pharmacist will advise you of the dose needed and how often you should
take it. Read the leaflet that comes with your particular brand for
further information.
How quickly do H2 blockers work?
Generally,
H2 blockers are well absorbed by the body and can provide quick relief
of symptoms from some problems. For example, heartburn caused by
reflux. However, if you are taking them for other reasons, such as to
heal an ulcer, it may take longer for the drugs to have an underlying
effect.
How long is treatment needed?
This can vary
depending on the reason for treating you, so speak to your doctor for
advice. In some cases your doctor may prescribe an H2 blocker to use
'as required'. This means you only take it when you need it to relieve
your symptoms, rather than every day. In some situations you may be
prescribed an H2 blocker to be taken every day.
Who can and cannot take H2 blockers?
H2
blockers may not be suitable for people with kidney problems or for
pregnant or breastfeeding mums. A full list of people who should not
take H2 blockers is included with the information leaflet that comes in
the drug packet. If you are prescribed or buy an H2 blocker, read this
to be sure you are safe to take it.
What about side-effects?
Most people who
take H2 blockers do not have any side effects. However, side effects
occur in a small number of users. The most common side effects are:
diarrhoea, headache, dizziness, rash and tiredness. For a full list of
side effects and possible interactions associated with your drug
consult the leaflet that comes with your medication.
Note:
taking some H2 blockers can affect how well other drugs work. In
particular, tell your doctor if you are taking the blood-thinning drug
warfarin or a drug for epilepsy called phenytoin (Epanutin). You should
also tell your doctor if you take theophylline, a drug commonly used to
treat asthma or COPD (chronic obstructive pulmonary disease).
If
you are taking antacids you should not take them at the same time as
you take you other medication, including H2 blockers. This is because
antacids can affect how well other medication is absorbed.
Other considerations
You should consult
your doctor if your symptoms worsen, or if you experience any of the
following problems which can indicate a serious gut disorder:
- Vomiting
blood. This may be obviously fresh blood, but altered blood in vomit
can look like ground coffee. Doctors call this 'coffee-ground vomit'.
- Blood in your stools (faeces). This may be obvious blood, or it may just make your stools black.
- Unintentional weight loss.
- Difficulty swallowing, including food getting stuck in the gullet.
- Persistent abdominal pain or persistent vomiting.
Disclaimer: This article is for information only and should not
be used for the diagnosis or treatment of medical conditions. EMIS and
PiP have used all reasonable care in compiling the information but make
no warranty as to its accuracy. Consult a doctor or other health care
professional for diagnosis and treatment of medical conditions.
© EMIS and PiP 2008 Reviewed: 16 Sep 2008
