Products
Acetylsalicylic acid is commercially available in the low dosage of 100 mg in the form of enteric-coated film-coated tablets (Aspirin Cardio, generics; in Germany and Austria, Aspirin Protect). The drug has been approved in many countries since 1992. Aspirin Cardio 300 mg is also used. In the United States, drugs with 81 mg (= 1.25 grains) and with 325 mg (= 5 grains) are commonly used. See also under acetylsalicylic acid (pain management).
Structure and properties
Acetylsalicylic acid (C9H8O4, Mr = 180.2 g/mol) exists as a white, odorless, crystalline powder or as colorless crystals and is sparingly soluble in water. It is an acetylated derivative of salicylic acid and belongs to the salicylates.
Effects
Acetylsalicylic acid (ATC B01AC06) has antiplatelet and antithrombotic properties. The effects are due to acetylation of cyclooxygenase-1 (COX-1) in platelets, resulting in irreversible inhibition of thromboxane A2 formation. Thromboxane A2 is an eicosanide that promotes platelet aggregation and induces vasoconstriction. The effects of acetylsalicylic acid persist throughout the approximately eight-day platelet life span. Because of its enteric coating, the drug is absorbed only in the intestine and exerts its effects prehepatically in the blood as it travels from the intestine to the liver.
Indications
For prevention and treatment of thrombotic, cardio- and cerebrovascular events, e.g., prophylaxis of myocardial infarction, stroke, and transient ischemic attack in high-risk patients.
Dosage
According to the package insert. The tablets are usually taken once daily. As of 2018, the package insert specifies that the tablets should be administered at least half an hour before eating. Higher doses (300 mg / 325 mg) increase the risk of side effects while maintaining efficacy (e.g., Campbell et al., 2007). Therefore, low doses (81 mg / 100 mg) are predominantly recommended for prevention today.
Contraindications
- Hypersensitivity, including to other salicylates and other NSAIDs, or asthma resulting from therapy with these substances
- Bleeding tendency
- Gastrointestinal ulcers
- Severe liver or kidney dysfunction
- Severe decompensated heart failure
- Combination with methotrexate (> 15 mg/week).
- Last third of pregnancy
Full precautions can be found in the drug label.
Interactions
Acetylsalicylic acid has potential for drug-drug interactions. Interactions have been described with methotrexate, anticoagulants, NSAIDs, ibuprofen, antiepileptic drugs, SSRIs, diuretics, glucocorticoids, and alcohol, among others.
Adverse effects
The most common potential adverse effects include gastrointestinal discomfort and microbleeding. To prevent these side effects, the tablets are coated with an enteric film. Another option is the fixed combination with a gastric protector ( acetylsalicylic acid and esomeprazole). Acetylsalicylic acid increases the bleeding tendency and can rarely cause severe bleeding, mainly in the digestive tract and brain.