Salicylate

Also known as: Salicylates

Formal name: Salicylic acid

Related tests: INR (International Normalised Ratio, prothrombin time)

At a Glance

Why Get Tested?

To monitor aspirin therapy of inflammatory disease such as rheumatoid arthritis to guard against overdosage, and to guide hospital treatment if aspirin overdosage is suspected

When to Get Tested?

At least 3 hours after the last dose of aspirin

Sample Required?

A blood sample taken from a vein usually in an arm

The Test Sample

What is being tested?

The plasma concentration of salicylic acid (the active part of aspirin) is being measured as this produces the undesirable side effects, notably damage to the stomach, including ulcers and bleeding, and tinnitus (ringing in the ears).

How is the sample collected for testing?

Normally from a vein in the arm by use of a needle and syringe.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

The Test

How is it used?

The plasma salicyate concentration is used to assess aspirin dosage and, if overdosage is diagnosed, to guide hospital treatment of aspirin poisoning.

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When is it requested?

Either to monitor dosage during long-term aspirin treatment, or to help diagnose overdosage.

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What does the test result mean?

During long-term aspirin treatment of rheumatic fever, rheumatic arthritis, and other inflammatory joint conditions, the plasma salicylate concentration is normally between 250 and 300 milligrams per litre (mg/L). After overdosage the result has to be interpreted by the hospital doctor who takes into account other factors such as the time the overdose was taken and whether other drugs are present

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Is there anything else I should know?

Aspirin should not be taken long-term without consulting your doctor and should NEVER be given to children under 16 years of age unless directed by a doctor. Aspirin should not be taken with alcoholic drinks as this increases the risk of bleeding from the stomach. If aspirin overdosage is suspected you should seek medical help. Ibuprofen (Neurofen) or paracetamol (Panadol) are safer treatments than aspirin for short-term problems such as headache.

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Common Questions

1. Will taking aspirin at normal dosage damage my health?

It is possible that taking aspirin regularly at the doses used to treat rheumatoid arthritis, for example, will damage your health. Regular asprin consumption should only be adopted under the supervision of your doctor. Low-dose aspirin (50 milligrams or so per day, suspended in water) used to reduce the risk of heart attack is generally safe.

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2. Why should aspirin not be given to children?

Rarely in children aspirin causes a type of liver disease known as Reyes Syndrome which may prove fatal. Aspirin should never be given to children unless directed by a doctor as it is sometimes used to treat conditions in which no other drug is as effective.

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3. Why is the test sometimes referred to as 'salicylates' and not simply 'salicylate'?

Other much less commonly used drugs than aspirin such as methylsalicylate (Oil of Wintergreen) may give similar results in the test, but this is of no consequence normally as the meaning of the result is the same.

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4. Why is the INR test sometimes requested in people taking aspirin?

Aspirin acts to prevent blood clotting and INR may be measured to ensure that this effect is not too pronounced, especially if other anticoagulant drugs are also being taken.

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5. What is salicylism?

Salicylism is the name given to the toxic effects salicylates experienced after overdosage, usually marked by tinnitus, nausea, and vomiting.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.