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Aspirin

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Created On: 22/01/2020

Aspirin is a nonsteroidal anti-inflammatory drug (NSAID).

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Introduction

Aspirin is a nonsteroidal anti-inflammatory drug (NSAID). It has analgesic, antipyretic, antirheumatic, and anti-inflammatory properties. Its action may be due to inhibition of synthesis and release of prostaglandins. It is used to treat pain, inflammation associated with various conditions (including rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis, and ankylosing spondylitis) and nonfatal myocardial infarction.

Pharmacological Class: NSAID

Indications

Pain
Inflammation
Fever
Muscle pain
Toothaches
Common cold
Headache
Rheumatic fever
Menstrual pain
Ankylosing Spondylitis
Osteoarthritis
Rheumatoid arthritis

Pharmachologic action

Aspirin directly and irreversibly inhibits the activity of both types of cyclooxygenase (COX-1 and COX-2) to decrease the formation of precursors of prostaglandins and thromboxanes from arachidonic acid. It may competitively inhibit prostaglandin formation. The platelet aggregation-inhibiting effect of aspirin specifically involves its ability to act as an acetyl donor to cyclooxygenase.

Irreversible acetylation renders cyclooxygenase inactive, thereby preventing the formation of the aggregating agent thromboxane A2 in platelets. Since platelets lack the ability to synthesize new proteins, the effects persist for the life of the exposed platelets (7-10 days). Aspirin may also inhibit production of the platelet aggregation inhibitor, prostacyclin (prostaglandin I2), by blood vessel endothelial cells.

Dosage

Osteoarthritis: 3 grams per day in divided doses

Rheumatoid Arthritis: 3 grams per day in divided doses

Ankylosing Spondylitis: 3 grams per day in divided doses

Fever: 325 to 650 mg orally or rectally every 4 hours as needed

Rheumatic fever: 80 mg/kg/day orally in 4 equally divided doses, up to 6.5 g/day

SLE: 3 grams per day in divided doses

Pharmacokinetics

Aspirin is absorbed rapidly in gastrointestinal tract. It is rapidly hydrolyzed primarily in the liver to salicylic acid, which is conjugated with glycine (forming salicyluric acid) and glucuronic acid and excreted largely in the urine.

Contraindications

People who are allergic to aspirin, products containing aspirin, or aspirin-like products
People with active reye's syndrome, kidney disease, gout, anemia, hemophilia and blood clotting disorder
Pregnant and breast feeding women
People who have habit of drinking too much of alcohol
Patient who are prescribed anticoagulation therapy

Drug interaction

Aspirin when taken with leflunomide may increases risk of liver damage
Concomitant use of aspirin and ibuprofen increases the risk of gastrointestinal ulcers, bleeding and reduces the effectiveness of aspirin
When taken together with methotrexate, causes nausea, vomiting, diarrhea, sore throat, chills, fever, rash, unusual bruising or bleeding, pale skin, dark urine, swelling of the extremities, or shortness of breath
Using omacetaxine together with aspirin may increase the risk of bleeding
Concomitant use of aspirin and ketorolac causes nausea, vomiting, stomach pain, drowsiness, black or bloody stools, coughing up blood, urinating less than usual, and shallow breathing

Side effects

Common (affecting between 1 in 10 to 1 in 100):

Heartburn
Upset stomach
Drowsiness
Mild headache
Epigastric distress
Dyspepsia
Nausea

Uncommon (affecting 1 in 100 to 1 in 1000):

Black/tarry stools
Persistent or severe stomach/abdominal pain
Slurred speech
Weakness on one side of the body
Sudden vision changes or severe headache

Very rare (affecting less than 1 in 10,000):

Serious bleeding from the stomach/intestine
Serious allergic reaction
Trouble breathing
Difficulty hearing

Precautions

Avoid in patients who have or have ever had asthma, frequent stuffed or runny nose, or nasal polyps
Avoid in patients who have three or more alcoholic drinks every day
Avoid in pregnant or breastfeeding women as it may harm fetus
Avoid in patients having heartburn, upset stomach, or stomach pain, ulcers, anemia, bleeding problems such as hemophilia, or kidney or liver disease

Clinical evidence

Seventy-two randomized single-dose trials with 3253 patients given aspirin, and 3297 were given placebo. Significant benefit of aspirin over placebo was shown for aspirin 600/650 mg, 1000 mg and 1200 mg, with numbers-needed-to-treat for at least 50% pain relief of 4.4 (4.0-4.9), 4.0 (3.2-5.4) and 2.4 (1.9-3.2) respectively. Type of pain model, pain measurement, sample size, quality of study design, and study duration had no significant impact on the results. There was a clear dose-response for pain relief with aspirin, even though these were single dose studies.¹

References

Pain 9 Jun;81(3):289-97
https://www.nlm.nih.gov/medlineplus/druginfo/meds/a682878.html
http://www.drugs.com/tips/aspirin-patient-tips#how_it_works
http://www.rxlist.com/aspirin-drug.htm
http://www.rxlist.com/aspirin-drug/overdosage-contraindications.htm
http://www.webmd.com/drugs/2/drug-1082-3/aspirin-oral/aspirin-oral/details/list-contraindications