At a Glance
Why Get Tested?
To determine the concentration of mycophenolic acid (MPA) in the blood in order to monitor levels and prevent toxicity
When to Get Tested?
As soon as mycophenolate therapy begins and whenever the dose is changed; may be ordered frequently at first, then at regular intervals; whenever excess or deficient levels of MPA are suspected
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
This test measures the amount of mycophenolic acid in the blood. Mycophenolic acid is the active metabolite of mycophenolate, a drug that is primarily given to people who have had a heart, kidney, or liver transplant to help prevent rejection and secondarily to people with a variety of autoimmune disorders.
Normally, a person's immune system defends the body against infections and can distinguish between self and non-self. The immune system recognizes a transplanted organ as non-self and begins to attack it. In the case of autoimmune disorders, the immune system mistakenly targets the body's own cells and tissues, causing damage and inflammation. Mycophenolate belongs to a group of drugs that suppress the immune system (immunosuppressants) and helps to prevent organ rejection, tissue inflammation, and damage. It acts by inhibiting the formation of an enzyme that is necessary for the production of special immune cells called T-lymphocytes and B-lymphocytes. This inhibition causes a decrease in the immune system function and in antibody production, reducing the body's immune response to transplanted organs or to its own tissues and cells.
Mycophenolate is given to organ transplant recipients in conjunction with other immunosuppressant drugs, such as cyclosporine and tacrolimus. In the treatment of autoimmune disorders, mycophenolate may be used as a single agent (although the person may also be taking other medications). It may be used for treating conditions such as systemic lupus erythematosus (SLE), vasculitis, rheumatoid arthritis, and Crohn disease.
There are two formulations of the drug available, mycophenolate mofetil and mycophenolate sodium. The drug is metabolized by the liver to form first the active mycophenolic acid (MPA) and then the inactive mycophenolic acid glucuronide (MPAG). Cells in the body turn some of the MPAG back into MPA. The level of MPA in the blood rises when MPA is first formed and then again when some of it is re-formed. Most MPAG, and small amounts of MPA, are eliminated from the body in the urine.
Doctors typically give a standard dose of mycophenolate and then monitor its effect clinically. Most immunosuppressants must be maintained within a narrow therapeutic range. If the level is too low, organ rejection may occur; if it is too high, then the person may develop toxicity. However, the therapeutic range for mycophenolic acid has not yet been fully established and physicians can manage most patients symptomatically.
When the physician chooses to monitor mycophenolic acid levels, the mycophenolic acid blood test is usually measured as a trough level and correlated to clinical side effects. It is timed so that the collection is just prior to the next dose at the drug's lowest concentration in the blood.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
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.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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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.
Sources Used in Current Review
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(©2010) American College of Rheumatology. Practice Management, Mycophenolate. Available online at http://www.rheumatology.org/practice/clinical/patients/medications/mycophenolate.asp through http://www.rheumatology.org. Accessed August 2011.
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