Aspirin, also known as acetylsalicylic acid (ASA), is a widely used nonsteroidal anti-inflammatory drug (NSAID) recognized for its ability to alleviate pain, reduce fever, and mitigate inflammation. Additionally, it serves an important role as an antithrombotic agent, helping to prevent heart attacks, strokes, and blood clots in individuals at high risk. The therapeutic benefits of acetylsalicylic acid have been known for at least 2,400 years.
Aspirin Chemical Structure
Aspirin is a synthesized derivative of salicylic acid. Its chemical structure is fundamental to its pharmacological properties.
Molecular Formula
The molecular formula of aspirin is C9H8O4, indicating that it consists of 9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atoms.
Molecular Weight
Acetylsalicylic acid has a molecular weight of approximately 180.16 g/mol.
Chemical Structure
The chemical structure of aspirin includes a benzene ring with two functional groups: an acetyl group (-COCH3) and a carboxylic acid group (-COOH). The acetyl group is attached at the ortho position, while the carboxylic acid group is at the meta position. The process of acetylation, involving the esterification of salicylic acid, introduces the acetyl group. During this reaction, the hydroxyl group (-OH) of salicylic acid reacts with acetic anhydride, forming acetylsalicylic acid. This reaction is catalyzed by an acid catalyst such as sulfuric acid. The acetyl group enhances the lipophilicity of acetylsalicylic acid , facilitating its absorption and distribution in the body.
IUPAC Name
The IUPAC name of acetylsalicylic acid is 2-Acetoxybenzoic acid, reflecting its chemical structure.
Mechanism of Action
Aspirin exerts its effects by irreversibly inhibiting the cyclooxygenase (COX) enzyme, which is crucial in the production of prostaglandins and thromboxanes. By inhibiting both COX-1 and COX-2, acetylsalicylic acid reduces inflammation, pain, and fever, and prevents platelet aggregation, which is essential in preventing blood clots.
Pharmacokinetics
Absorption
Aspirin is rapidly absorbed from the stomach and intestine through passive diffusion. It is a prodrug that is converted into salicylate, the active metabolite responsible for its therapeutic effects, in the stomach, intestinal mucosa, blood, and predominantly in the liver.
Distribution
Salicylate distributes quickly into body fluid compartments and binds to albumin in the plasma. As total plasma salicylate concentrations increase, the unbound fraction also rises. Salicylate can cross the placental barrier and is present in breast milk.
Metabolism
Aspirin is swiftly transformed into salicylate, which is primarily metabolized by the liver. The major pathway involves conjugation with glycine, which becomes saturated at higher doses, leading to longer half-life and nonlinear kinetics at high concentrations.
Excretion
Urinary excretion of unchanged salicylate accounts for 10% of total elimination, involving glomerular filtration, active proximal tubular secretion, and passive tubular reabsorption. Urinary excretion is pH-dependent, with increased excretion at higher pH levels.
Therapeutic Uses
Acetylsalicylic acid has a broad range of therapeutic applications:
Pain Relief
Aspirin is effective for mild to moderate pain, including muscle aches, toothaches, common cold, and headaches. The typical dose for pain relief is 325-650 mg every 4 to 6 hours.
Fever Reduction
As an antipyretic, acetylsalicylic acid is used to reduce fever, with a typical dose of 325-650 mg every 4 to 6 hours.
Anti-inflammatory
Aspirin’s anti-inflammatory properties are beneficial in treating conditions such as rheumatoid arthritis. It is classified as an NSAID.
Cardiovascular Protection
A low dose of acetylsalicylic acid is used to prevent heart attacks and strokes. It is often prescribed for cardiovascular protection under medical supervision.
Prevention of Blood Clots
Acetylsalicylic acid helps prevent blood clots, protecting bypass grafts and stents in the heart. It is also used in the prevention of certain cancers and in treating rheumatic fever.
Other Uses
Aspirin is used to manage certain types of arthritis and rheumatic fever.
It is crucial to use aspirin under healthcare professional supervision, with dosages and frequency adjusted based on the condition being treated.
Side Effects
Serious Side Effects
Serious side effects may require immediate medical attention, including:
- Abdominal pain, cramping, or burning
- Black, tarry stools
- Bloody or cloudy urine
- Confusion
- Chest pain or discomfort
- Fainting
- Seizures
- Unusual bleeding or bruising
Other Side Effects
Less severe side effects may include:
- Acid or sour stomach
- Anxiety
- Dizziness
- Dry mouth
- Stomach discomfort
It is essential to consult with a healthcare provider if any side effects persist or worsen.
Acetylsalicylic Acid Drug Interactions
Aspirin can interact with numerous medications, affecting its efficacy and increasing the risk of adverse effects.
Number of Interactions
Acetylsalicylic acid is known to interact with 343 drugs, with 51 major, 247 moderate, and 45 minor interactions.
Types of Interactions
Aspirin can interact with prescription and over-the-counter medications, vitamins, and herbal products.
Examples of Interactions
Some medications that may interact with acetylsalicylic acid include:
- Benadryl (diphenhydramine)
- Crestor (rosuvastatin)
- Eliquis (apixaban)
- Fish Oil (omega-3 fatty acids)
- Plavix (clopidogrel)
Always consult with a healthcare professional before starting or stopping any medication.
Safety Considerations
Medication Interactions
Aspirin can cause adverse reactions when taken with other medications or substances. Consultation with a healthcare professional is essential.
Medical Conditions
Acetylsalicylic acid should be used cautiously in individuals with conditions such as ulcers, bleeding disorders, or respiratory conditions like asthma.
Pregnancy and Breastfeeding
Aspirin is not recommended during late pregnancy or breastfeeding without medical advice.
Dietary Factors
Certain foods and drinks can interact with aspirin, increasing side effects. Professional guidance is recommended.
Serious Side Effects
Aspirin use can lead to serious side effects, including gastrointestinal bleeding and kidney failure. Professional evaluation is necessary to determine the appropriateness of aspirin therapy.
Regulatory Status
United States
In the U.S., aspirin is available over-the-counter and by prescription. The USPSTF recommends individualized decisions for daily acetylsalicylic acid use for cardiovascular disease prevention in adults aged 40 to 59 with significant CVD risk.
Europe
In Europe, low-dose aspirin access is more restricted, often requiring a prescription. Guidelines provide specific recommendations for acetylsalicylic acid use in VTE prophylaxis.
Other Countries
Aspirin’s regulatory status varies globally, with differing availability and regulations based on intended use.
Contraindications
Aspirin should not be used in the following situations:
Allergies
Individuals with allergies to aspirin or other NSAIDs should avoid it.
Bleeding Disorders
Aspirin is contraindicated in patients with bleeding disorders or a recent history of gastrointestinal bleeding.
Respiratory Conditions
Those with asthma, rhinitis, or nasal polyps may experience severe allergic reactions to acetylsalicylic acid.
Gastrointestinal Conditions
Patients over 60 or with a history of GI problems are at higher risk for serious GI events.
Hypertension
Aspirin may increase blood pressure and diminish the effects of antihypertensive agents.
Liver and Kidney Disease
Patients with liver or kidney disease should use aspirin cautiously.
Pregnancy and Breastfeeding
Aspirin is not recommended during late pregnancy or breastfeeding without medical advice.
Other Medications
Concurrent use with certain medications can increase the risk of adverse effects.
Consultation with a healthcare professional is essential before starting or stopping any medication.
| Aspect | Details |
|---|---|
| Therapeutic Uses | Pain relief, fever reduction, anti-inflammatory, cardiovascular protection, blood clot prevention, arthritis |
| Dosage | Pain relief: 325-650 mg every 4-6 hours; Fever reduction: 325-650 mg every 4-6 hours |
| Side Effects | Serious: Abdominal pain, black stools, confusion, chest pain; Other: Sour stomach, anxiety, dizziness |
| Drug Interactions | 343 known interactions: Major: 51, Moderate: 247, Minor: 45 |
| Safety Considerations | Caution in bleeding disorders, respiratory conditions, pregnancy, breastfeeding |
| Contraindications | Allergies to NSAIDs, bleeding disorders, recent GI bleeding, asthma, liver, and kidney disease |
Always consult with a healthcare professional for accurate guidance on acetylsalicylic acid use.
