Acetylsalicylic acid

Updated on All content is checked by medical journalists.

Acetylsalicylic acid (ASA) is one of the most successful drugs. It is used as a pain reliever, fever reliever, anti-inflammatory and as a platelet inhibitor to prevent blood clots (e.g. after a heart attack). The first drug with ASA as an active ingredient came on the market in 1899. There are now numerous other preparations. Here you can read everything you need to know about acetylsalicylic acid.

This is how acetylsalicylic acid works

Acetylsalicylic acid (ASA) inhibits the formation of prostaglandins - tissue hormones that play an important role in inflammatory processes, the mediation of pain and fever. Acetylsalicylic acid has an analgesic, antipyretic, anti-inflammatory and anti-rheumatic effect.

The inhibiting effect on the release of prostaglandins has another effect. Normally, prostaglandins promote blood clotting. By preventing the release of prostaglandins, acetylsalicylic acid also has an anticoagulant effect.

It also has "blood-thinning" properties. As a platelet inhibitor (thrombocyte aggregation inhibitor), ASA prevents the platelets from sticking together - the blood remains fluid, so that blood clots cannot form so easily, which could then clog a vessel in the heart or brain.

Thus, acetylsalicylic acid is suitable for the prevention of heart attacks and strokes in high-risk patients. The dosages required for this area of application are significantly lower than when ASA is given to reduce pain and fever.

Uptake, breakdown and excretion

Acetylsalicylic acid taken orally is rapidly and almost completely absorbed into the blood in the stomach and small intestine. When they are processed in the body, the active substance salicylic acid is mainly produced.

While the acetylsalicylic acid itself is broken down quite quickly, the breakdown of the resulting salicylic acid takes longer, the higher the dose of acetylsalicylic acid taken.

Salicylic acid is mainly excreted through the kidneys.

When is acetylsalicylic acid used?

The areas of application (indications) of the higher dosed (500 to 3,000 milligrams per day) acetylsalicylic acid are:

mild to moderate pain (such as headaches, migraines, back pain)
Fever and pain associated with colds and flu-like infections

Indications for low-dose (100 to 300 milligrams per day) acetylsalicylic acid are:

Acute and follow-up treatment of acute myocardial infarction
Coronary artery disease with unstable chest tightness (angina pectoris)
Prevention of blood clots after arterial surgery
Transient ischemic attack (TIA) and stroke prevention

This is how acetylsalicylic acid is used

Acetylsalicylic acid is usually used orally, that is, taken up through the mouth - usually in the form of tablets. The anticoagulant and blood-thinning effect unfolds even at low doses, while higher doses of acetylsalicylic acid are necessary for pain relief, lowering of fever and anti-inflammatory effects.

ASA should not be taken on an empty stomach because it irritates the stomach lining and in the worst case can lead to gastrointestinal ulcers and bleeding. In addition, the drug should always be taken with a sufficient amount of liquid (for example a glass of water).

Acetylsalicylic acid and other pain relievers should not be taken for more than three days in a row and no more than ten days per month without medical advice.

Combination preparations with acetylsalicylic acid

Acetylsalicylic acid is also available in combination with other active ingredients, which result in an improved overall effect (e.g. blood thinning or pain relief). For example, there are blood-thinning combination preparations made from acetylsalicylic acid and another anticoagulant (clopidogrel, dipyridamole). Also available is a combination of ASA (used to inhibit blood platelets), atorvastatin (used to lower cholesterol) and ramipril (used to treat high blood pressure and heart failure).

Pain relievers containing acetylsalicylic acid, paracetamol and caffeine (used to treat tension headaches and mild migraines) are also available.

What are the side effects of acetylsalicylic acid?

Side effects of acetylsalicylic acid are particularly evident in the gastrointestinal tract because the active ingredient can damage the mucous membrane. As a result, more than ten percent of all patients who take acetylsalicylic acid develop stomach pain or tiny bleeding (microbleeding) in the digestive tract, for example.

In higher doses, nausea, vomiting, diarrhea, gastrointestinal ulcers, anemia due to iron deficiency (iron deficiency anemia) and dizziness can occur.

Between one and ten percent of users react to taking acetylsalicylic acid with nausea, vomiting and / or diarrhea.

In less than one percent of patients, acetylsalicylic acid causes, for example, disorders of the acid-base balance, hearing disorders (tinnitus), visual disorders, states of confusion, drowsiness (somnolence), allergic skin symptoms and spasms of the airways muscles (bronchospasm).

Changes in the blood count (such as a reduction in white blood cells) and water retention in the tissue (edema) are also possible. The latter can occur because more water and sodium ions are retained in the body.

In addition, acetylsalicylic acid can cause Reye's syndrome - a rare, life-threatening disease of the brain and liver. It can especially occur in children between the ages of four and nine who have a viral infection and who are receiving ASA. Exactly how this can lead to the development of Reye's syndrome has not yet been clarified. It is also unknown how often Reye's syndrome occurs in connection with the intake of acetylsalicylic acid.

Reye's syndrome is the reason why acetylsalicylic acid can only be given to children under the age of twelve with a doctor's prescription!

When should I not take acetylsalicylic acid?

Contraindications

In certain cases, acetylsalicylic acid must never be used. These absolute contraindications include:

Gastrointestinal ulcer or bleeding
allergic reactions to salicylates

In addition, acetylsalicylic acid may in many cases only be given if a doctor assesses the benefit of the application in the specific individual case to be higher than the associated risks (such as gastrointestinal bleeding). These so-called relative contraindications include:

bronchial asthma
Hearing loss (hypacusis)
simultaneous use with other anticoagulant drugs (exception: low-dose heparin therapy)

Interactions

Caution is advised when using acetylsalicylic acid in patients with nasal polyps, chronic inflammation of the nose and sinuses with polyp formation (chronic hyperplastic rhinosinusitis) or asthma. You may react to pain relievers such as acetylsalicylic acid with an asthma attack (analgesic asthma).

When used at the same time, acetylsalicylic acid can increase the effectiveness of the following drugs:

Digoxin and Digitoxin (heart medicines)
Lithium (for manic-depressive disorders etc.)
Methotrexate (for rheumatism, cancer)
Triiodothyronine (for hypothyroidism, etc.)

In addition, acetylsalicylic acid can reduce the effects of the following substances:

Spironolactone, canrenoate, loop diuretics (water tablets)
High blood pressure drugs (antihypertensive drugs)

Age restriction

ASA preparations for self-medication may only be used from the age of twelve. It can also be used under the age of 12 with a doctor's prescription.

pregnancy and breast feeding period

Acetylsalicylic acid should not be taken in the first and second trimester of pregnancy (1st and 2nd trimester) unless the doctor deems it absolutely necessary and prescribes its use. In the last trimester of pregnancy, the active ingredient must not be taken under any circumstances.

This does not apply to the low-dose administration of ASA (100 to 300 milligrams per day), as directed by a doctor. If indicated, this can be carried out throughout pregnancy.

Occasional use of acetylsalicylic acid is permitted during breastfeeding. In general, women should consult a doctor before using any drug while breastfeeding (such as during pregnancy).

How to get medicines with the active ingredient acetylsalicylic acid

Preparations with acetylsalicylic acid do not require a prescription in Germany, Austria and Switzerland and are available in pharmacies. This does not apply to drugs that contain a prescription drug in addition to acetylsalicylic acid.

Since when has acetylsalicylic acid been known?

Acetylsalicylic acid is a derivative of salicylic acid. This pain reliever and antipyretic agent was first isolated from the herbaceous meadowsweet plant in 1835.

However, another plant, the white willow - in Latin - gave its name Salix alba. Already in 1829 it was out Salix-Extracts the substance salicin extracted, from which the salicylic acid can be produced.

The pure salicylic acid corrodes the lining of the mouth and stomach, which is why researchers have been looking for an alternative for a long time. It was found by the German chemist Felix Hoffmann. He succeeded in synthesizing acetylsalicylic acid for the first time in 1897. He let the salicylic acid react with an acetic acid derivative, resulting in the better tolerated acetylsalicylic acid. The first drug with this active ingredient finally came on the market in 1899.

What else you should know about acetylsalicylic acid

The anticoagulant effect of acetylsalicylic acid and thus the increased bleeding tendency persist for several days even after the drug is discontinued. Therefore, acetylsalicylic acid must be discontinued in good time before an operation.

Tags: organ systems Diseases symptoms