How acetylsalicylic acid works
Acetylsalicylic acid (ASA) inhibits the formation of prostaglandins – tissue hormones that play an important role in inflammatory processes, pain mediation and fever. Thus, acetylsalicylic acid has analgesic, antipyretic, anti-inflammatory and antirheumatic effects.
The inhibitory effect on the release of prostaglandins has another effect. Normally, prostaglandins promote blood clotting. By preventing the release of prostaglandins, acetylsalicylic acid therefore also has an anticoagulant effect.
In addition, it has “blood-thinning” properties. As a blood platelet inhibitor (thrombocyte aggregation inhibitor), ASA prevents the blood platelets from clumping together – the blood remains thin, so that blood clots cannot form so easily and then possibly block a vessel in the heart or brain.
This makes acetylsalicylic acid suitable for preventing heart attacks and strokes in patients at risk. For this area of application, the required dosages are significantly lower than when ASA is given to reduce pain and fever.
Absorption, degradation and excretion
Orally ingested acetylsalicylic acid is rapidly and almost completely absorbed into the blood in the stomach and small intestine. When it is processed in the body, it mainly produces the active substance salicylic acid.
Salicylic acid is excreted mainly by the kidneys.
When is acetylsalicylic acid used?
The indications for use (indications) of higher-dose (500 to 3,000 milligrams per day) acetylsalicylic acid are:
- mild to moderate pain (such as headache, migraine, 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 post-treatment of acute myocardial infarction.
- Coronary artery disease with unstable chest tightness (angina pectoris).
- Prevention of blood clots after arterial surgical procedures
- Prevention of transient ischemic attacks (TIA) and strokes
How acetylsalicylic acid is used
Acetylsalicylic acid is usually used orally, that is, taken by mouth – usually in tablet form. The anticoagulant and blood-thinning effects develop at low doses, while higher acetylsalicylic acid doses are needed for pain relief, fever reduction and anti-inflammation.
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 sufficient liquid (for example, a glass of water).
Combination preparations with acetylsalicylic acid
Acetylsalicylic acid is also available in combination with other active ingredients, resulting in an improved overall effect (for example, blood thinning or pain relief). For example, there are blood-thinning combination preparations of acetylsalicylic acid and another anticoagulant (clopidogrel, dipyridamole). Also available are the combination of ASA (for platelet inhibition), atorvastatin (for cholesterol reduction) and ramipril (for high blood pressure and heart failure).
In addition, pain relievers containing acetylsalicylic acid, acetaminophen, and caffeine (to treat tension headaches and mild migraines) are available.
What are the side effects of acetylsalicylic acid?
Side effects of acetylsalicylic acid are most apparent in the gastrointestinal tract because the active ingredient can damage the mucous membrane. As a result, more than ten percent of all patients taking acetylsalicylic acid develop stomach pain or tiny bleedings (microbleeds) in the digestive tract, for example.
At higher doses, nausea, vomiting, diarrhea, gastrointestinal ulcers, anemia due to iron deficiency (iron deficiency anemia), and dizziness may also occur.
Between one and ten percent of users react to taking acetylsalicylic acid with nausea, vomiting and/or diarrhea.
Furthermore, blood count changes (such as a reduction in white blood cells) and water retention in the tissues (edema) are 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 occur primarily in children between the ages of four and nine who suffer from a viral infection and receive ASA. Exactly how this can lead to the development of Reye’s syndrome is not yet clear. It is also unknown how frequently Reye’s syndrome occurs in connection with the use of acetylsalicylic acid.
Reye’s syndrome is the reason why acetylsalicylic acid may only be given to children under twelve years of age on a doctor’s prescription!
When should acetylsalicylic acid not be taken?
Contraindications
In certain cases, acetylsalicylic acid must not be used under any circumstances. These absolute contraindications include:
- gastrointestinal ulcers or bleeding
- allergic reactions to salicylates
- Bronchial asthma
- hearing loss (hypacusis)
- concomitant use with other anticoagulant drugs (exception: low-dose heparin therapy)
Drug interactions
Caution should be exercised 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 analgesics such as acetylsalicylic acid with an asthma attack (analgesic asthma).
When used at the same time, acetylsalicylic acid may increase the effectiveness of the following drugs:
- Digoxin and digitoxin (heart medicines).
- Lithium (for manic-depressive disorders, etc.)
- Methotrexate (for rheumatism, cancer)
- Triiodothyronine (in hypothyroidism, etc.)
In addition, acetylsalicylic acid may reduce the effects of the following substances:
- Spironolactone, canrenoate, loop diuretics (diuretic agents).
- @ Antihypertensives (drugs for high blood pressure)
Age restriction
ASA preparations for self-medication may only be used from the age of twelve years. If prescribed by a doctor, use is also possible under the age of 12.
Pregnancy and lactation
This does not include the medically guided low-dose use of ASA (100 to 300 milligrams per day). This can be carried out throughout pregnancy if indicated.
During breastfeeding, occasional use of acetylsalicylic acid is permitted. In general, however, women should consult a doctor before any drug use during breastfeeding (just as during pregnancy).
How to obtain medicines containing acetylsalicylic acid
Preparations containing acetylsalicylic acid do not require a prescription and are available in pharmacies in Germany, Austria and Switzerland. Exceptions to this are medicines that contain a prescription drug in addition to acetylsalicylic acid.
How long has acetylsalicylic acid been known?
Acetylsalicylic acid is a derivative of salicylic acid. This analgesic and antipyretic active ingredient was first isolated from the herbaceous plant meadowsweet in 1835.
However, it was named after another plant, the silver willow – Salix alba in Latin. As early as 1829, the substance salicin, from which salicylic acid can be produced, was extracted from salix extracts.
What you should also know about acetylsalicylic acid
The anticoagulant effect of acetylsalicylic acid and thus the increased bleeding tendency continue for several days after the drug is discontinued. Therefore, acetylsalicylic acid must be discontinued in good time before a surgical procedure.
