Firstly, an important note; this entry should not be taken as advice, it is only information. The person to seek for advice on medication is your doctor.

Why do We Take Aspirin? And What is It Really?

We all take Aspirin at some point or another to relieve the uncomfortable sensation of a headache or the after-effects from the overindulgence of the night before. Though far from being a panacea, its general role in modern society is to relieve pain.

A Short History

The roots of this drug lie way back in ancient Greece, where Hippocrates used a bitter powder derived from willow bark to relieve aches and pains. This powder contained substances in a family known as salicylates, of which Aspirin is a member. The prefix salicyl- is from the Latin name for willow, Salix alba.

Plant-derived salicylates such as sodium salicylate were used in the 1800s to combat the pain associated with arthritis, and it was this which prompted Felix Hoffman to work on a new, artificial salicylate. His father suffered from arthritis, and took sodium salicylate to combat the pain. However, it was very bitter, and it also gave him stomach irritation. Hoffman wanted to make a drug which had the pain-relieving aspects of sodium salicylate, but which was less acidic, thus with reduced stomach irritating properties, and more pleasant to swallow.

In 1899¹, he came up with was a chemical called acetylsalicylic acid (ASA), which did precisely that. It was later renamed to what we know it as today: Aspirin.

He had created the world's first purely synthetic drug.

At the time, Bayer and Company, the dyestuffs and pharmaceutical company that employed Hoffman, thought that it would not be commercially viable. This was because they suspected, wrongly, that it would give people a weak heart.

Aspirin, despite being challenged with other relatively newer pain relievers such as paracetemol and ibuprofen, is still the world's best selling analgesic. Hoffman's employer, Bayer is now the world leader in aspirin production, selling on average, 11 billion tablets a year.

The name Aspirin is in fact a registered trademark, and is thus still owned by Bayer. (This is why in this entry Aspirin will be referred to with a capital 'A'.)

Other, cheaper versions of ASA are available under different trade names, such as:

• ASS-ratiopharm
• Godamed
• Boxazin-S
• Alcacyl
• Bufferin
• ASS (in Germany)
• ASA (in UK)
• Anacin
• Ascriptin
• Coricidin D
• Darvon Compound
• Ecotrin
• Empirin
• Equagesic
• Excedrin
• Fiorinal
• Gelprin
• Norgesic
• Percodan
• Robaxisal
• Soma Compound
• Talwin
• Compound
• Vanquish

What Is It?

Aspirin is a common NSAID; a member of the Non-Steroidal Anti-Inflammatory Drug family. Its close relatives include paracetemol² and ibuprofen. The NSAID title essentially means that it is not a steroid but reduces inflammation.

To understand how we relieve pain via Aspirin and other drugs of its ilk, we have to know how pain is created. Now pain itself is a very individual thing; not all the same actions cause pain in different people, eg variations on bumps and knocks, how much one drinks and so on. But the pain sensation essentially comes from an action which stimulates a group of nerve sensors called pain receptors. Signals are then sent to the brain, which processes the information, and sends an appropriate response.

Aspirin vs Pain

Round 1 - How It Works

The pain response is poorly understood, even by those who know it well, and involves several long and incomprehensible words. But some aspects of this response are better understood than others, notably the one which Aspirin is concerned with.

This response is the formation of local hormones called prostaglandins, from arachidonic acid. Both are natural substances found in the body. These are released from certain cells which go on to stimulate aspects of the body's immune system and lead to inflammation. The theory is that this also leads to the feeling of pain.

Now, assuming that this is the only response which leads to the feeling of pain, there is a relatively easy way of stopping it from happening, or at least preventing it from getting any worse; stop the synthesis of prostaglandins from arachidonic acid, which is what Aspirin does. This prevents further inflammation and as a result, prevents pain from getting any worse.

Round 2 - Faltering against Pain

So far so good. However, there are certain flaws to Aspirin being a great pain remover.

• It isn't actually that strong; on encountering a really bad hangover, something which can be taken at higher doses due to less severe side effects, such as a soluble ibuprofen, is probably more suited to the job.

• Pain is not simply created by one response, but is in fact a multi-stage response. So although the prostaglandin response is the main problem, it is not the only one. As a result, pain may only be dulled and not relieved.

• Being a NSAID, it comes with its fair share of side effects, the most important being the risk of stomach ulcers.

Round 3 - It's not just Pain

Now remember the prostaglandins? This substance may have the downside of creating pain, but has many upsides as well. The main one is that it prevents too much acid being created in the stomach. Preventing prostaglandins from being created means that this control is lost. Now the worst that most people may feel is slight heartburn, but the absolute worst scenario may be a stomach ulcer, especially on repeated use, and also taking regularly on an empty stomach.

The Rematch

So what can be done to maximise the effect of Aspirin at relieving pain, or for that matter, its close relations, paracetemol and ibuprofen?

• Don't take while drunk. Your liver will be too busy trying to break down excess alcohol that you have drunk to process Aspirin properly, and hence take longer to work. It is also extremely foolish; you may have a bad reaction.

• Take it after or during a meal. Avoid if possible taking on an empty stomach.

• For the quickest pain relief, use the dissolving 'fizzy' type of Aspirin or related drug, as this gets absorbed much quicker.

Aspirin vs Clotting

The Explanation

Pain relief is not the only reason that Aspirin is commonly taken. In fact, it is commonly prescribed to those who have high blood pressure or have been diagnosed with heart disease for one interesting feature - it is an 'anticoagulant'; in other words, it thins the blood.

To understand how Aspirin works in this aspect also involves several long and incomprehensible words, with a few unintelligible acronyms and ill thought-out alpha-numeric identification tags thrown in for good measure. So here is a more simplified explanation.

Aspirin acts on a process called the 'clotting cascade', so-called as this involves the response to bleeding or damage to blood vessels, which is the action of natural substances inside the body called enzymes, which stimulate other enzymes, which stimulate others, and so on. Hence a 'cascade'. The upshot of all this is that if even a small bleed is detected, then the response is quick. The bigger the bleed, the quicker and larger the cascade.

Aspirin works by blocking the activation of an enzyme in the clotting cascade, hence slowing the formation of any clot. As a result, blood is thinned and clots in the wrong places at wrong moments are unlikely to form.

It also has another effect. Platelets are essential to clot formation, as they aggregate, or group together at the site, forming a loose plug. This is the foundation of a clot. Aspirin also prevents platelets from aggregating, hence preventing clot formation.

Round 1 - Heart Disease and 'Hypertension'

The theory is that high blood pressure or 'hypertension' is partly caused by the clotting cascade being active at the wrong time, ie when there is no bleeding, or damage to blood vessels caused by high blood pressure. Due to this, blood is thicker, and pressure rises in the circulation. The heart has to work harder against the thicker blood. This may eventually lead to heart failure if untreated.

Round 2 - Deep Vein Thrombosis

The other theory is that inactivity, such as being bedridden in hospital or on long haul flights, can increase the chances of Deep Vein Thrombosis (DVT) formation. Being inactive for such a long time can cause the slowing of the flow of blood up the legs. Veins are relatively thin, and require being squeezed by surrounding muscle to propel blood back up toward the heart. Their inactivity could cause blood to clot in the deep veins of the legs, forming a DVT.

At this stage, your life is not in danger. In fact, you are quite safe. The problem is that it has the potential to become much worse. Should there be a change in the status quo, ie a sudden burst of activity, such as getting up out of bed, the clot may dislodge, shooting up toward the heart, where due to the ingenious one-way pump system it gets lodged in the arteries supplying the lungs.

This is what is known as a pulmonary embolism³. What results from this is that blood, with no access to the lungs, cannot be reoxygenated, and death follows if you cannot get treated quickly. This is why many doctors say that 20 mins before getting on the flight, take a couple of Aspirin tablets on a full stomach to aid circulation.

As a further reminder, although DVTs are a worry for people, especially going on long haul flights, they are relatively uncommon (although not unheard of) in healthy adults as a result of going on an 11-hour flight. They are more commonly found in long-stay bedridden patients, especially the elderly, in those with broken legs or recovering from hip replacement, or in those who stay immobile for several weeks. These are not the events that the press like to report about, as they are less sensational than 'economy-flight syndrome', as DVT has been dubbed.

But digressing aside; as mentioned in the first few paragraphs, Aspirin is far from being a panacea - the cure-all for all ailments. In fact, there are some instances in which aspirin should not be taken at all.

Contra-indications of Aspirin

Consider the contra-indication of Aspirin in asthmatics. Why? Well this is all down to the prostaglandins again. Borne of arachidonic acid, pain-causing (in theory) and acid-reducing. But arachidonic acid isn't just solely a prostaglandin-producing necessity; instead, it parents a whole family of other substances, some of which are involved in allergic asthma.

Allergic Asthma

Now the tendency of medical science to give such processes the unnecessary technobabble make over has been stressed throughout this entry. So here are the simplified reasons not to take aspirin if you are an asthmatic.

Aspirin blocks the pathway in which prostaglandins are synthesised from arachidonic acid. This must mean that there is more arachidonic acid about which would normally synthesise something else.

In allergic asthma, the airways react by swelling up-in other words, they become inflamed; reducing the diameter of the airways, causing the characteristic wheeze and the tightness of chest. Now this is caused by three substances, all in the leukotriene family, one of which is histamine. These three substances are also borne of arachidonic acid, and it is here the connection with Aspirin is made.

The Logic of the Matter is This...

If there is more arachidonic acid than normal because it cannot synthesise prostaglandins, then in order for the body to strike a balance, more of these leukotrienes must be released.

The result of all this on the poor asthmatic is that Aspirin makes asthma a lot worse than needs be. Asthma attacks caused by Aspirin are often so bad that it requires a trip to the local casualty ward. This is why your GP will tell asthmatics to take paracetemol and avoid Aspirin, as paracetemol has so little to virtually no anti-inflammatory action; ie it doesn't reduce the production of inflammatory prostaglandins, and hence doesn't make asthma attacks worse.

On the subject of the downside of Aspirin, it may be wise to mention its side effects.

Side Effects of Aspirin

• Stomach ulcers and bleeding - rare, but it has been documented on overdose and long-term large dose self-administration.

• Dizziness

• Deafness and tinnitus (ringing in the ears) - on regular self-administration of large doses of Aspirin.

• Hyperventilation - on overdose due to the blood being too acidic. Remember that aspirin is converted into an acid when transported in the blood, so too much can make the blood too acidic.

Long Term use of Aspirin

Those prescribed Aspirin long term for Cardiac conditions or for blood thinning reasons tend to be prescribed an Aspirin known as Enteric Coated Aspirin. This means the Aspirin doesn't dissolve until it's passed through the stomach, thus eliminating possible side effects of stomach bleeds/ulcers in long term use. Also worth noting that due to the Enteric coating it makes this type of Aspirin unsuitable for pain relief, as even after passing through the stomach it is slow dissolving.

If on other Drugs...

Aspirin is such a successful drug because it can actually be taken with lots of other drugs. Here are a few which can be taken concurrently with Aspirin and or ASA:

• Codeine phosphate; this is often sold as a combination tablet with ASA
• Morphine
• Caffeine
• Paracetemol
• Phenylephrine; this is sold combined with ASA in cold and cough remedies such as Beechams Powders(R).

This list is just an example, but if you are on any medication, ask a pharmacist to see if you can take Aspirin with what you are already on.

In Conclusion

So what can we do? Well, no drug, prescribed or over the counter is wholly safe. You can even die of overeating if you really try. Remember that Aspirin and ASA are only safe at the recommended dosage and for the recommended length of time. Also, listen to your doctor. They didn't go through six years of medical school and several years of junior doctor hell to tell you untruths.

Medical advice, differing from medical scientists by being rarely unintelligible, should always be sought if unsure of taking Aspirin, for example, when pregnant or taking other prescribed medication.

Please Note: h2g2 is not a definitive medical resource. If you have any health concerns you must always seek advice from your local GP. You can also visit NHS Direct.