ACETYLSALICYLIC 300MG TABLET

Indications

• Mild to moderate pain relief
• Fever reduction
• Management of inflammatory conditions such as rheumatoid arthritis and osteoarthritis
• Prevention of cardiovascular events in patients with a history of myocardial infarction or stroke
• Management of acute coronary syndrome

Dosage

Children: Refer to the BNF for Children for appropriate dosing in paediatric patients, as this may differ significantly from adult dosing.

Adults: Refer to the BNF for specific dosing guidelines, as doses may vary based on the indication and patient factors.

Mechanism of action

Aspirin works primarily by irreversibly inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, leading to a decrease in the synthesis of prostaglandins and thromboxanes. This results in reduced inflammation, pain, and fever. The inhibition of COX-1 also reduces platelet aggregation by decreasing thromboxane A2 production, which is crucial for platelet activation and aggregation.

Pharmacodynamics

The analgesic effects of aspirin are attributed to its ability to inhibit the generation of prostaglandins, which mediate pain and inflammation. In addition to its pain-relieving and anti-inflammatory effects, aspirin's antiplatelet action is significant in the context of cardiovascular health, as it reduces the risk of thrombus formation in blood vessels.

Pharmacokinetics

Aspirin is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 1 to 2 hours after oral administration. It is extensively metabolized in the liver, primarily via hydrolysis to salicylic acid, which has its own therapeutic effects. The elimination half-life varies depending on the dose, ranging from 15 to 20 minutes for aspirin and several hours for salicylic acid. Aspirin and its metabolites are excreted primarily in the urine.

Contra-indications

• Active gastrointestinal bleeding
• History of peptic ulcer disease
• Severe renal impairment
• Severe hepatic impairment
• Hypersensitivity to acetylsalicylic acid or other NSAIDs
• Children and teenagers with viral infections (risk of Reye's syndrome)

Adverse effects

• Gastrointestinal irritation and bleeding
• Nausea and vomiting
• Dyspepsia
• Allergic reactions such as rash or asthma exacerbation
• Tinnitus (ringing in the ears)
• Renal impairment
• Hepatic dysfunction

Interactions

• Increased risk of gastrointestinal bleeding with other NSAIDs or anticoagulants
• Enhanced effects of anticoagulants (e.g., warfarin, heparin)
• Reduced effectiveness of antihypertensive drugs (e.g., ACE inhibitors)
• Increased risk of renal impairment with diuretics
• Potential interaction with methotrexate, leading to increased toxicity

Precautions

• Use with caution in patients with a history of gastrointestinal disorders
• Monitor renal function in long-term use or in patients with renal impairment
• Assess the risk of bleeding before surgery or dental procedures
• Caution in patients with asthma or nasal polyps due to potential hypersensitivity reactions
• Consider the potential for Reye's syndrome in children and adolescents

Pregnancy

Use during pregnancy is generally not recommended, particularly in the third trimester, due to the risk of adverse effects on the fetus and complications during delivery.

Breast-feeding

Acetylsalicylic acid is excreted in breast milk; caution is advised if used while breastfeeding.

Storage

Store in a cool, dry place away from direct sunlight. Keep out of reach of children.

Formulations

• Tablets
• Enteric-coated tablets
• Effervescent tablets
• Suppositories
• Oral suspension