Adverse
and allergic reactions to aspirin and NSAIDSAspirin is a useful painkiller
Aspirin has long been used to reduce
pain from inflammation and injury, as well as fever. Originally
isolated from Willow Tree Bark and other plants in the early 1800's,
natural salicylates were found to be effective for the treatment
of pain and fever. Unfortunately, these products were very irritating
to the stomach. Later, artificial salts of these natural products
were made, and found to be just as effective but with less side-effects.
These days, aspirin is made synthetically, and a number of similar
synthetic non-steroidal anti-inflammatory drugs (NSAIDS), have
been introduced.
Aspirin also reduces inflammation
Compounds known as prostaglandins play
an important role in tissue inflammation, pain and fever. Production
of prostaglandins is inhibited by aspirin and related medications
(NSAIDS), because these medications inhibit an enzyme known as
cyclooxygenase-1, (COX-I). Because aspirin also inhibits the activity
of blood elements known as platelets (which help clotting), aspirin
also thins the blood, thus reducing the risk of heart attacks
and strokes. There is also recent evidence that aspirin may even
reduce the risk of bowel cancer .
All drugs are potential poisons; aspirin
is no exception
Common side effects of aspirin include
bruising and stomach upset (or even ulcers or bleeding from the
bowel), at high dose. Very high doses may cause confusion or ringing
in the ears (tinnitus). It should also be avoided in children,
as aspirin can trigger a condition as Reye's syndrome, where severe
liver inflammation occurs.
Allerghic reactions to aspirin may occur
Mild to severe allergic reactions to
aspirin may occur. Symptoms include flushing, itchy rashes, blocked
and runny noses and severe difficulty breathing or asthma, usually
within an hour of taking a tablet. When assessing reactions to
aspirin or similar medications, it is useful to look for evidence
of underlying disease such as hives (urticaria), nose / sinus
disease or asthma. This is because the presence of some medical
conditions increases the likelihood of aspirin allergy.
How common is aspirin allergy?
Normal population 1%
Ongoing hives/urticaria 30%
Inactive hives 10%
Asthma 20%
Asthma /sinus disease/ polyps 30%
The presence of aspirin is not always obvious
Aspirin is present in many across-the-counter
pain-killers as well as various sinus tablets, medicines used
to control period pain and cold & flu tablets. If you are
sensitive to aspirin, you will need to carefully read medicine
labels and be cautious about taking any pain-killer without talking
to your doctor or pharmacist first.
There are many brands of NSAIDS
Because there are so many brand names
of the same medication, and so many types of medications available,
accidental exposure to NSAIDS may occur. It is therefore important
to tell your pharmacist or health professional about your sensitivity
to these medicines.
Testing for drug sensitivity
The mechanism by which allergic reactions
to aspirin and related pain-killers occur is uncertain. There
is no reliable blood or skin allergy test which has been proven
to be useful for confirming or excluding sensitivity to these
medicines. The only way to do so is to do a graded open challenge
under strict medical supervision. Challenge testing is not always
necessary, but may be advised in some circumstances: to prove
that sensitivity exists, or to prove the safety of an unrelated
medicine, so that you have another drug from which to choose if
you need to use a pain killer.
What is aspirin desensitisation?
This is useful in selected patients
with the "aspirin triad", a condition in which patients
suffer from aspirin allergy, nasal polyps and asthma. Even though
these patients are allergic to aspirin, most can be made to tolerate
high doses by starting off at a very low dose of aspirin initially
and increasing it day by day. Once a higher dose is reached (generally
1 4 tablets/day), there is reduced production of inflammatory
chemicals known as leucotrienes. As leucotrienes can worsen asthma
and polyp growth, aspirin desensitisation can reduce asthma severity,
the rate of polyp regrowth, and the severity of sinusitis. The
decision to undertake aspirin desensitisation is best made by
an allergy specialist.
Side-effects of aspirin desensitisation
Reasons for undertaking aspirin desensitisation in aspirin sensitive patients
Management of aspirin / NSAID sensitivity
Ongoing hives
If you have on-going hives or urticaria,
you should avoid aspirin and NSAIDS unless you know that you can
tolerate them without a problem. If you are already taking regular
aspirin (for example, to thin the blood), or a regular arthritis
tablet for treatment of pain, then you do not need to stop this
medicine unless their hives clearly get much worse after taking
a tablet.
Acute hives/severe allergic reactions after
a pain-killer
Most people with aspirin/NSAID allergy are sensitive to only one
drug. Unfortunately, up to 1 in 5 may have unpredictable cross-reactive
allergic responses to similar medicines. Under these circumstances,
an open challenge with a completely different drug can be considered
if you need to take a pain killer for treatment of pain.
"Aspirin Triad": Aspirin sensitive
asthma/ nasal polyps/ sinusitis/rhinitis
Leucotriene "blockers"/antagonists (such as Singulair
/ montelukast) or aspirin desensitisation (are useful options.
Tolerability of new NSAIDS: the COX-II inhibitors
A number of new medicines have been introduced in the last few
years, which inhibit an enzyme known as Cyclooxygenase II (COX-II).
Many of these drugs (eg. Celebrex, Vioxx) have some inhibitory
reaction on COX-I as well. Whilst they cause less stomach irritation
than aspirin and traditional NSAIDS, some patients will have allergic
reactions to these as well. Published estimates are of the order
of 5 to 20 %.
Dietary salicylates in aspirin-sensitive
patients
Occasional patients who are allergic to aspirin, and have the
"aspirin triad", will suffer symptoms if they eat foods
that have high levels of natural salicylates. This affects the
occasional patient rather than the majority, and low salicylate
diets are not considered a routine part of management.
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