ACETYLSALICYLIC ACID

In the U.S., acetylsalicylic acid is mostly marketed as aspirin and is used to treat pain (such as headache and joint pain, for example) in addition to fever and rheumatism. Available over the counter, it also has antiplatelet properties that can help prevent a stroke.

CHEMICAL NAME

2-acetoxybenzoic acid

MEDICINES

Acetylsalicylic acid is primarily found in aspirin tablets designed to treat headaches (325 mg) or to act as an antiplatelet (81 mg). However, acetylsalicylic acid is also found in hundreds of other OTC medications, either by itself or in combination with other ingredients intended to treat colds and coughs.

HOW IT WORKS

Acetylsalicylic acid is also called a blood thinner or antiplatelet because of its ability to prevent blood cells called platelets from forming a clot. Preventing clot formation (thrombosis) in a blood vessel can protect a person from a heart attack or stroke. Acetylsalicylic acid achieves its pain-reducing effect by suppressing the production of prostaglandins—lipid mediators that can heighten the sensation of pain.

SIDE EFFECTS

Acetylsalicylic acid has a rather long list of side effects—ranging from bleeding (nosebleeds, bleeding gums, unusual bruising, and cuts that won’t stop bleeding) to allergic reactions (hives, asthma attack, and swelling of the face and throat that can cause difficulty in breathing). An overdose can result in nausea, ringing in the ears, hearing loss, and signs of stomach bleeding, including pain, cramping, and bloody, black, or tarry stools.

INTERACTIONS

Taking aspirin at the same time as an anticoagulant (warfarin, heparin, and newer drugs such as apixaban [Eliquis]) can cause serious bleeding. Aspirin increases the concentration of psychotropic drugs such as lithium and barbiturates—which can increase their toxicity. It also heightens the effectiveness of sulfonylureas (antidiabetic drugs). A possible result: hypoglycemia (low blood sugar). Studies have also shown that acetylsalicylic acid reacts not only with other medicines to cause interactions but also with foodstuffs. Grapefruit juice, for example, heightens the effect of this painkiller. There are also warnings about combining blood thinners such as acetylsalicylic acid with large amounts of foods that contain vitamin K (such as spinach and broccoli).

PROPER USE

A standard adult aspirin tablet contains 325 mg of acetylsalicylic acid. The recommended dose is one or two tablets every four to six hours. Unless otherwise directed by a physician, the maximum daily dose is 4,000 mg. Important: Even low doses of aspirin increase the risk of bleeding. This remains true even if the last dose was taken several days earlier. If you are going to have surgery, inform the doctor that you are taking (or have taken) aspirin. This applies to minor surgery as well.