Mycophenolate is metabolized in 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. Concentrations of MPA in the blood rise 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.
Normally, a persons immune system defends the body against infections and can distinguish between self and nonself. It recognizes a transplanted organ as foreign and begins to attack it. In the case of autoimmune disorders, the immune system mistakenly targets the bodys own cells and tissues. Mycophenolic acid belongs to a group of immunosuppressant drugs and helps to prevent organ rejection, tissue inflammation, and damage. It acts by inhibiting the formation of an enzyme that is necessary for T-lymphocyte and B-lymphocyte proliferation. This causes a decrease in immune system function and in antibody production.
Mycophenolate is given to organ transplant patients 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 patient may also be taking other medications). Like other immunosuppressant agents, mycophenolate may cause side effects and adverse reactions and is associated with an increased risk of infection and the development of lymphoma.
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 concentration is too low, organ rejection may occur; if it is too high, then the patient 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 drugs 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.
Is any test preparation needed to ensure the quality of the sample?No test preparation is needed.
How is it used?The mycophenolic acid (MPA) test is ordered to measure the amount of drug in the blood. Unlike other immunosuppressant drugs, the therapeutic range for MPA has not yet been established, and the physician may order levels to monitor drug interaction with other immunosuppressants in combination therapy or to correlate with clinical symptoms and side effects.
Since mycophenolic acid can lower white blood cell counts and cause anemia, a complete blood count (CBC) will frequently be ordered along with the mycophenolic acid test to evaluate the bodys blood cell status. Other tests may also be periodically ordered to evaluate organ function as MPA levels can be affected by changes in kidney and liver function.
When is it ordered?Mycophenolic acid test and CBC are ordered frequently at the start of therapy and then at intervals for as long as the patient is taking mycophenolate. The MPA test may be performed whenever there is a change in dosage, a change in other medications that the patient is taking, or whenever a patient has symptoms that suggest side effects, toxicity, or organ rejection.
What does the test result mean?Concentrations that are too high may cause toxicity. Concentrations that are too low may lead to rejection of the transplanted organ. Since the therapeutic range is not yet fully established, doctors will rely on the patients clinical signs and their own expertise in addition to drug levels to help guide treatment and adjust dosage if necessary.
If the person is also taking another immunosuppressant and/or other medications, then all of them will need to be in balance. Patients should work closely with their doctor and transplant team.
Is there anything else I should know?Mycophenolic acid levels can be affected by other medications. Drugs that reduce MPA concentrations include antacids and cholestyramine. Drugs that can increase MPA include ganciclovir, probenecid, and acyclovir. Herbal supplements such as Echinacea, Cats Claw, and St. Johns wort should be avoided while taking mycophenolate.
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. Patients who become pregnant should talk to their doctor about the associated risks.
Those who are taking mycophenolate should talk to their doctor before getting any vaccines.
Patients may have side effects and experience complications such as infections and slow healing even when taking mycophenolate properly. Side effects may include:
- Muscle pain
- Stomach pain
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 doctor 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 doctor will usually send your tests consistently to one laboratory for testing.
Should I tell my other health care 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 (such as skin cancers and lymphoma).