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
Mycophenolic acid (MPA) 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. This test measures the amount of mycophenolic acid in the blood.
Normally, a healthy immune system distinguishes the body's own healthy tissue (self) from threats such as viruses, bacteria, and parasites (non-self). However, the immune system recognizes a transplanted organ as non-self and may 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 called immunosuppressants that suppress the immune system and helps to prevent organ rejection, tissue inflammation, and damage. Mycophenolate acts by inhibiting formation of an enzyme necessary to produce special immune cells called T-lymphocytes and B-lymphocytes. Inhibiting lymphocyte formation decreases both immune system function and antibody production, reducing the body's immune response to transplanted organs or to its own tissues and cells.
Organ transplant recipients receive mycophenolate in conjunction with other immunosuppressant drugs such as cyclosporine and corticosteroids. Autoimmune disorder patients may be prescribed mycophenolate as a single agent, although they may take other medications. It has been used to treat lupus (especially with symptoms of kidney disease), rheumatoid arthritis, vasculitis, inflammatory bowel disease such as Crohns disease, inflammatory eye diseases including iritis and scleritis, and some other kidney or skin disorders.
Mycophenolate, like 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. The mycophenolic acid blood test uses blood samples collected when the drugs are at their lowest, typically just prior to the next dose. Such levels are called trough levels and they are correlated to clinical side effects.
How is it used?
The mycophenolic acid (MPA) test is ordered to monitor the amount of the drug in the blood over time in organ transplant recipients who are taking the drug to prevent organ rejection. The test is used to determine whether the drug concentration is within the therapeutic range and is below the toxic level. Treatment with MPA is monitored because the range in which the drug is effective but not toxic is very narrow.
A healthcare practitioner may order an MPA test to monitor drug interaction with other immunosuppressants in combination therapy or to correlate with clinical symptoms and side effects. If someone is taking MPA in addition to cyclosporine or tacrolimus, the healthcare practitioner will order both MPA as well as the other immunosuppressant drug tests.
When is it ordered?
MPA and complete blood count (CBC) tests are ordered frequently at the start of therapy and then at intervals for as long as the person is taking mycophenolate. The MPA test may be performed whenever there is a change in dosage, a change in other medications that the person is taking, or whenever someone has persistent side effects, toxicity, or organ rejection.
The most common side effects include:
- Upset stomach or pain
- Nausea and/or vomiting
- Sleeplessness (insomnia)
- Muscle pain
Some side effects can be serious. If any of the following become severe or persistent, the person's healthcare provider should be notified, who may wish to check the level of drug:
- Swelling of the hands, arms, feet, ankles or lower legs
- Difficulty breathing
- Chest pain
- Fast heartbeat
- Dizziness, fainting, lack of energy
- Pale skin
- Black or tarry stools, blood in stools
- Bloody vomit
People older than age 65 may have increased risk for some side effects, particularly infections and gastrointestinal bleeding.
What does the test result mean?
An MPA level that is higher than the therapeutic range may cause toxicity. A level that is below the range may lead to rejection of the transplanted organ. Depending on the results, a healthcare practitioner may adjust the dose that the person is given.
Monitoring blood levels can help establish the range in which mycophenolic acid is therapeutic for a particular individual (i.e., individualize therapy). The level at which the person has minimal side effects but is not rejecting the organ is the target range for that person. If other immunosuppressants and/or drugs are added or illnesses occur, the healthcare provider can adjust the dose of mycophenolic acid, if necessary, until the blood level falls within the individualized therapeutic range for this person.
In addition to MPA levels, what other tests might be ordered?
Since MPA can lower white blood cell counts and cause anemia, a healthcare practitioner usually orders a complete blood count (CBC) along with MPA to evaluate the blood cells. Other tests, such as a liver panel or renal panel, may also be periodically ordered to evaluate organ function since MPA levels can be affected by changes in kidney and liver function.
Is there anything else I should know?
Mycophenolic acid levels can be affected by other medications. Drugs that reduce MPA concentrations include antacids containing magnesium or aluminum hydroxide and cholestyramine. Drugs that can increase MPA include ganciclovir, probenecid, and acyclovir. Herbal supplements such as Echinacea, Cats Claw, and St. John's wort should be avoided while taking mycophenolate.
A partial list of medications that may also interfere with mycophenolate includes:
- Azathioprine (Imuran)
- Trimethoprim/sulfamethoxazole (Bactrim)
- Theophylline (Theo-Dur)
- Phenytoin (Dilantin)
- Aspirin and other salicylates
Oral contraceptives can interfere with MPA, while MPA can decrease the effectiveness of oral contraceptives and has been linked with first trimester miscarriages and congenital birth defects. Women should not become pregnant while taking mycophenolate and should not breastfeed. Two forms of birth control are recommended as is a pregnancy test prior to the start of the medication. Women who become pregnant should talk to their healthcare practitioner about the associated risks.
Those who are taking mycophenolate should talk to their healthcare provider before getting any vaccines. MPA could increase risk of infection.
People may have side effects and experience complications such as infections and slow healing even when taking mycophenolate properly. Like other immunosuppressant agents, MPA is associated with an increased risk of infection and the development of both lymphoma and skin cancer. People who take MPA should avoid exposure to sunlight and wear protective clothing and sunscreen (SPF 30 or higher) when they are outdoors.
How long will I need to be on mycophenolate?
Typically, mycophenolate is given long term, but it depends on your condition and how you respond to the drug. Mycophenolate is one choice in an array of medications that may be used to help treat your condition. If you are a transplant patient, you must take an immunosuppressant (or combination of drugs) throughout your life. If you are a patient with an autoimmune disorder, then you will be prescribed medications to help limit damage to your body and to alleviate symptoms. Talk to your healthcare provider about the best choices for your condition. These choices may change over time.
Where are mycophenolic acid tests performed?
Mycophenolic acid tests may be performed in a local hospital laboratory but will frequently be sent to a reference laboratory. Because different laboratories use different methods and will have slightly different reference ranges, your healthcare practitioner will usually send your tests consistently to one laboratory for testing.
Should I tell my other healthcare providers that I am taking mycophenolate?
Yes. This is important information for them, partially because of drug interactions and partially because of the immunosuppressant action of mycophenolic acid. It can affect your ability to heal, to get vaccinations, and may increase the risk of developing certain cancers, including skin cancers and lymphoma.