Aspirin

Definition

Aspirin, acetylsalicylic acid, is a drug used to treat mild pain , reduce fever and inflammation, and prevent heart attacks and strokes.

Description

Aspirin is a derivative of salicylic acid, which has been used medicinally for thousands of years. The first record of its use survives from ancient Egypt, about 3,500 years ago. Plant products containing salicylates are described in the Ebers papyrus. Hippocrates, Celsus, Pliny the Elder, Dioscorides, and Galen all recommended decoctions containing salicylate for rheumatic pain. In 1763, Edward Stone reported in England what may have been the first clinical trial of salicylates using willow bark that had been dried and suspended in tea, beer, or water.

Natural preparations of salicylates, although effective for pain relief and reduction of fever, frequently caused stomach upset. According to the Aspirin Foundation, which is supported by Bayer Healthcare, a major international marketer of aspirin, salicylic acid was first synthesized in 1859 and was marketed as an antiseptic, although it was of no value for that purpose. Acetylsalicylic acid was first prepared by the French chemist Charles Gerhardt in 1853, but he did not succeed in identifying its structure and did not attempt to market the product. Aspirin was first marketed for medicinal uses around 1900. The name aspirin was used as a trademark by Bayer and is still a protected trademark in some nations, although in others, including the United States, the term is now considered the generic name for the compound.

The mechanism of action of aspirin was first reported by Sir John Vane (1927–2004) in 1971. For this achievement, he was awarded the 1982 Nobel Prize in Medicine and received his knighthood in 1983. He found that aspirin has both pain-killing and anti-inflammatory action.

The professional labeling of aspirin, the information provided to physicians and surgeons, includes the following uses:

• Reduces the combined risk of death and nonfatal stroke in patients who have had ischemic stroke or transient ischemia of the brain due to fibrin platelet emboli
• Reduces the risk of vascular mortality in patients with a suspected acute myocardial infarction (MI, heart attack). A 2007 review indicated that aspirin may be more effective for this purpose in men than in women.
• Reduces the combined risk of death and nonfatal MI in patients with a previous MI or unstable angina pectoris. There is no evidence that aspirin can reduce the risk of a first heart attack, and daily aspirin has not been recommended for persons who have not had a heart attack.
• Reduces the combined risk of MI and sudden death in patients with chronic stable angina pectoris.
• Relieves signs and symptoms of rheumatoid arthritis, juvenile rheumatoid arthritis, osteoarthritis, spondyloarthropathies, and arthritis and pleurisy associated with systemic lupus erythematosis (SLE)

For general use, aspirin serves for short-term relief of pain due to the following:

• Headache (including migraine and tension headaches)
• Pain and fever of colds
• Muscle aches and pains
• Menstrual pain
• Toothache pain
• Minor aches and pains of arthritis

There have been observations that people using aspirin on a regular basis may have a lower frequency of some conditions including breast and colon cancer and dementia. There are no conclusive studies to back these observations, which are anecdotal only. However, in one study, two non-steroidal anti-inflammatory drugs (NSAIDs), which would have been expected to have the same benefits as aspirin, failed to provide any protection against dementia.

Recommended dosage

For relief of minor pain and fever, the usual dose is 650 milligrams every 4 hours as needed. High dose regimens are normally discontinued when stomach upset occurs or when individuals experience tinnitus , ringing in the ears, which is a sign of aspirin toxicity.

• Ischemic stroke and TIA: 50 to 325 mg once a day; continue therapy indefinitely.
• Suspected acute MI: The initial dose of 160 to 162.5 mg administered as soon as an MI is suspected. The maintenance dose of 160 to 162.5 mg a day is continued for 30 days post-infarction. After 30 days, consider further therapy based on dosage and administration for prevention of recurrent MI.
• Prevention of recurrent MI: 75 to 325 mg once a day; continue therapy indefinitely. In the immediate aftermath of an MI, aspirin is commonly used in conjunction with other anticoagulant drugs such as warfarin, clopidogrel, or dipyridamole. The decision regarding how long to continue other drugs is usually left to the clinician.
• Unstable angina pectoris: 75 to 325 mg once a day; continue therapy indefinitely.
• Chronic stable angina pectoris: 75–325 mg once a day. Continue therapy indefinitely l CABG: 325 mg daily starting 6 hours post-procedure; Continue therapy for 1 year post-procedure.
• Rheumatoid arthritis: Initial dose is 3 g a day in divided doses. Increase as needed for anti-inflammatory efficacy with target plasma salicylate levels of 150 to 300 mcg/mL. At high doses (i.e., plasma levels of greater than 200 mcg/mL), the incidence of toxicity increases.
• Juvenile rheumatoid arthritis: Initial dose is 90 to 130 mg/kg/day in divided doses. Increase as needed for anti-inflammatory efficacy with target plasma salicylate levels of 150 to 300 mcg/mL. At high doses (i.e., plasma levels of greater than 200 mcg/mL), the incidence of toxicity increases.
• Spondyloarthropathies: Up to 4 g per day in divided doses.
• Osteoarthritis: Up to 3 g per day in divided doses.
• Arthritis and pleurisy of SLE: The initial dose is 3 g a day in divided doses. Increase as needed for anti-inflammatory efficacy with target plasma salicylate levels of 150 to 300 mcg/mL. At high doses (i.e., plasma levels of greater than 200 mcg/mL, the incidence of toxicity increases.

Precautions

Aspirin should not be used by people with known sensitivity to the drug, by people with liver or kidney insufficiency, or by people with blood coagulation disorders. People taking anti-coagulant drugs should consult their physician before taking aspirin.

QUESTIONS TO ASK YOUR PHARMACIST

• What are the benefits of special formulations of aspirin, including buffered and coated tablets?
• Is there a difference between generic and brand name products?
• What possible side interactions could there be with the medications I already take?

Because salicylates lower blood sugar, they should be used with caution by diabetics. Use of aspirin or other salicylate may require adjustment of insulin dosages.

Aspirin is particularly harmful to the stomach and should be avoided or used with caution by people with stomach ulcers or a history of stomach ulcers.

Side effects

The most common adverse effects of aspirin are related to harm to the stomach and intestines. The most frequently seen problems are nausea, vomiting, stomach pain, and heartburn .

Other side effects and adverse effects may be more serious. The following adverse effects require prompt medical attention: hives; rash;swelling of the eyes, face, lips, tongue, or throat; wheezing or difficulty breathing; hoarseness; fast heartbeat; fast breathing; cold, clammy skin;ringing in the ears; loss of hearing; bloody vomit; vomiting material that looks like coffee grounds; bright red blood in stools; and black or tarry stools.

Interactions

Aspirin may reduce the effectiveness of angiotensin converting enzyme (ACE) inhibitors, drugs used to lower blood pressure . If high dose aspirin is required, blood pressure must be monitored and dosages may need adjusting.

Aspirin, when used at the same time as acetazolamide (used for treatment of glaucoma ) may lead to elevated acetazolamide levels.

Aspirin should be used with care when taken with warfarin (an anticoagulant). Although it is common to use these two drugs in combination in patients after a heart attack , aspirin may increase blood levels of warfarin. Monitoring of coagulation time is essential.

Aspirin may reduce the effects of beta-blockers (used to lower blood pressure, regulate the heart rate, and for other purposes).

KEY TERMS

Angina pectoris —Severe chest pain caused by inadequate blood supply to the heart.

Embolus —Blockage of an artery by a blood clot.

Fibrin —A fibrous protein which is part of a blood clot.

Ischemic stroke —A form of stroke caused by a clot blocking the blood supply to the brain.

Juvenile arthritis —

Myocardial infarction —A heart attack caused by a blood clot blocking blood supply to the heart.

Osteoarthritis —A form of joint pain caused by deterioration of the cartilage at the ends of joint.

Salicylates —Compounds formed from reactions with salicylic acid.

Tinnitus —Ringing in the ears.

Transient ischemic attack (TIA) —A mini-stroke, a short period of inadequate blood supply to the brain, usually marked by blurred vision, dizziness, numbness.

Vascular —Pertaining to the circulatory system, the arteries, veins, and microcirculation.

The effectiveness of diuretic drugs may be reduced when taken at the same time as aspirin.

Salicylate can inhibit renal clearance of methotrexate (used for treatment of some cancers, some skin diseases, and forms of arthritis), leading to bone marrow toxicity, especially in the elderly or renally impaired.

Aspirin should not be used in combination with other NSAIDs, since their adverse effects are very similar and additive toxicity may occur.

Caregiver concerns

The first warning of aspirin toxicity is tinnitus, ringing in the ears. This effect may be less pronounced in people with high frequency hearing loss , which is common in the elderly. Additional monitoring may required.

Aspirin with a strong vinegar-like order should not be used. This is a sign that the aspirin has degraded into acetic acid (vinegar) and salicylic acid. Store aspirin in a dry location, since moisture accelerates this break-down.

Aspirin should be taken with a full glass of water to reduce the risk that the tablets will get stuck in the throat.

Sustained action and delayed action aspirin tablets should never be crushed.

Resources

PERIODICALS

Newton, J. L. “Improving the Gastrointestinal Tolerability of Aspirin in Older People.” Clin Interv Aging 1, no. 1 (2006): 33–39.

Yerman, T., W. Q. Gan, and D. D. Sin. “The Influence of Gender on the Effects of Aspirin in Preventing Myocardial Infarction.” BMC Med 18, no. 5 (October 2007): 29.

Feskanich, D., C. Bain, A. T. Chan, et al. “Aspirin and Lung Cancer Risk in a Cohort Study of Women: Dosage, Duration, and Latency.” Br J Cancer 97, no. 9 (November 5, 2007): 1295–1299.

Aronow, W. S. “Antiplatelet Therapy in the Treatment of Atherothrombotic Disease: Considering the Evidence.” Geriatrics 62, no. 4 (April 2007): 12–24.

Sam Uretsky PharmD