Aspirin: Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Acetylsalicylic Acid
Brand Name(s):
- Pakistan: Disprin, Aspro
- India: Ecospirin, Aspirin
- United States: Bayer Aspirin, Bufferin
- United Kingdom: Aspro Clear, Alka-Seltzer
2. Pharmacological Class
Class: Nonsteroidal Anti-inflammatory Drug (NSAID)
Subclass: Salicylate
3. Mechanism of Action
Aspirin inhibits the activity of cyclooxygenase (COX) enzymes, which are responsible for the synthesis of prostaglandins involved in inflammation, pain, and fever. Aspirin also irreversibly inhibits platelet aggregation by acetylating platelet cyclooxygenase, leading to the inhibition of thromboxane A2 formation.
4. Indications
Primary Indications: Relief of mild to moderate pain (headache, dental pain, muscle pain), fever reduction, and anti-inflammatory effects in conditions such as arthritis.
Off-label Uses: Prevention of cardiovascular events, including heart attacks and strokes.
5. Dosage and Administration
Standard Dosage:
- Adults (for pain and fever): 325-650 mg every 4-6 hours as needed.
- Adults (for cardiovascular prevention): 75-325 mg once daily.
- Route of Administration: Oral (tablets, chewable tablets, enteric-coated tablets).
Special Populations:
- Pediatric: Use is not recommended in children under 12 years of age without specific medical advice.
- Geriatric: Use lower doses to avoid adverse effects, particularly gastrointestinal bleeding and renal impairment.
6. Pharmacokinetics
Absorption: Aspirin is rapidly absorbed from the stomach and upper small intestine.
Distribution: It is widely distributed throughout the body, including crossing the placenta and being excreted in breast milk.
Metabolism: Metabolized in the liver to salicylic acid, primarily by conjugation with glycine or glucuronide.
Excretion: Excreted mainly through urine as metabolites.
Half-life: Approximately 2-3 hours.
7. Contraindications
Aspirin is contraindicated in patients with a history of hypersensitivity reactions to aspirin or other NSAIDs, and in patients with active peptic ulcer disease or a history of gastrointestinal bleeding.
8. Warnings and Precautions
Use caution in patients with asthma, renal impairment, hepatic impairment, and heart failure.
Long-term use of aspirin may increase the risk of gastrointestinal bleeding, kidney problems, and cardiovascular events.
9. Side Effects
Common Side Effects: Upset stomach, heartburn, and abdominal pain.
Serious Side Effects: Gastrointestinal bleeding, allergic reactions, and Reye's syndrome (in children).
10. Drug Interactions
Major Interactions: Anticoagulants (warfarin), antiplatelet drugs (clopidogrel), corticosteroids, and selective serotonin reuptake inhibitors (SSRIs).
Moderate Interactions: Methotrexate, diuretics, and ACE inhibitors.
Minor Interactions: Alcohol and certain antihypertensive drugs.
11. Pregnancy and Lactation
Pregnancy Category: Aspirin is generally not recommended during the third trimester of pregnancy due to potential risks to the fetus. Use in the first and second trimesters should be avoided if possible.
Breastfeeding Considerations: Aspirin is excreted in breast milk, but at usual doses, it is unlikely to cause harm to the nursing infant.
12. Patient Counseling Information
Key Points for Patients:
- Take aspirin exactly as directed on the label or as prescribed by your doctor.
- Do not take aspirin for fever in children or teenagers without consulting a doctor due to the risk of Reye's syndrome.
- Inform your doctor about all other medications you are taking, including over-the-counter drugs and supplements.
Administration Tips:
- Take aspirin with a full glass of water to prevent stomach upset.
- If using enteric-coated tablets, swallow them whole; do not crush or chew.