To determine the level of sirolimus in the blood in order to establish a dosing regimen, maintain therapeutic levels, and detect toxic levels
Sirolimus
Sirolimus
Also Known As
Rapamycin
[Often referred to by brand name (see MedlinePlus Drug Information)]
Formal Name
Sirolimus
This article was last reviewed
on
This article waslast modified
on December 26, 2018.
At a Glance
Why Get Tested?
When To Get Tested?
As soon as sirolimus therapy begins and whenever dose is changed; frequently at first, then at regular intervals to monitor concentrations over time; whenever excess or deficient levels are suspected
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None; the sample is typically collected 12 hours after the last dose and immediately prior to the next dose, or as directed by your healthcare provider
Accordion Title
Common Questions
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How is it used?
The sirolimus test is used to monitor the level of the drug over time in kidney transplant recipients who are taking the drug to prevent organ rejection. This test measures the amount of drug in the blood to determine whether the concentration is within the therapeutic range and is below the toxic level. Treatment with sirolimus must be monitored because the range in which the drug is effective but not toxic is very narrow.
If someone takes both sirolimus and cyclosporine (or tacrolimus), then both drug levels will be monitored.
Other tests may also be periodically ordered to evaluate organ function and blood cell counts because sirolimus may decrease a person's platelet count, increase blood lipids, and, when taken long-term with other immunosuppressants, affect kidney function.
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When is it ordered?
Sirolimus is ordered frequently at the start of therapy. Because of the long time that it takes to clear the drug from the body (its long half-life), the sirolimus concentration may take some time to reach a steady state (equilibrium) in the blood. Once dosages have been optimized for the individual and are well tolerated, then the frequency of sirolimus testing may be reduced.
The test may be performed whenever there is a change in dose, a change in other medications, or whenever the transplant recipient has symptoms that suggest side effects, toxicity, or organ rejection.
Even when taking sirolimus properly, some people may have side effects and experience complications, such as infections and slow healing. Other side effects include:
- Constipation
- Diarrhea
- Fever
- Headache
- Hypertension
- Increased levels of lipids in the blood
- Sleeplessness (insomnia)
- Nausea
- Sensitivity to sunlight
- Weight gain
If any of the above persist or becomes severe, the healthcare provider should be notified.
Additionally, some of the more dangerous signs and symptoms that warrant an immediate call to the health practitioner include:
- Cough, shortness of breath
- Chest pain
- Fast heart rate
- Pale skin
- Unusual bleeding or bruising
- Swollen, red, cracked, scaly skin
- Hives, rash, itching
- Difficulty swallowing
- Swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles or lower legs
- Hoarseness
Monitoring is necessary as long as the transplant recipient takes sirolimus.
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What does the test result mean?
A level that is higher than the established therapeutic range may cause symptoms associated with toxicity. An inappropriately low level may lead to rejection of the transplanted organ. Depending on the results, a health practitioner may adjust the dose that the person is given.
If the person is also taking other immunosuppressants or medications, then that person should work closely with their healthcare provider and transplant team to ensure that there is no potential interaction between the medications.
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Is there anything else I should know?
Drugs that inhibit or accelerate the metabolism of sirolimus may affect blood levels. Be sure to tell you healthcare provider about any drugs or supplements you are taking. Examples of drugs that can increase sirolimus blood levels include antifungal medications, clarithromycin, erythromycin, isoniazid, protease inhibitors, and quinidine. Examples of those that can decrease sirolimus levels include carbamazepine, phenobarbitol, phenytoin, rifampin and nafcillin. Grapefruit juice and herbal supplements such as St. John's Wort must be avoided while taking sirolimus.
People taking sirolimus should not alter their dose or the time that they take their dose without consulting their healthcare provider. Sirolimus should be taken consistently with respect to meals. Women should not become pregnant while taking sirolimus. Those considering pregnancy should talk to their health practitioner about associated risks.
Sirolimus should not be used with certain drugs that weaken the immune system and increase risk of infection. These include voriconazole, natalizumab, and rituximab. People taking sirolimus should also talk to their healthcare provider before getting any vaccines.
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How long will I need to be on sirolimus?
Transplant recipients must take immunosuppressants — including sirolimus or other drugs, often in combination — throughout their lives. Talk to your healthcare provider about the best choices for your condition; they may change over time.
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Who orders sirolimus tests?
Sirolimus will usually be monitored by the healthcare provider and transplant team that performed your surgery or by a health practitioner who has specific knowledge of transplantation and your condition.
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Where are sirolimus tests performed?
Sirolimus tests may be performed in a local hospital laboratory but may also be sent to a reference laboratory. Because different laboratories use different methods, each laboratory will have different reference ranges. Your healthcare provider will usually send your tests consistently to one laboratory for testing so that your levels can trend over time by the same testing method.
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Is sirolimus given to patients who receive organs other than kidneys or have other conditions?
Sirolimus also is used sometimes to treat psoriasis. This medication should not be given to prevent rejection of liver or lung transplants because it can cause serious and deadly side effects.
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Should I tell my other healthcare providers that I am taking sirolimus?
Yes. This is important information for them, partially because of drug interactions and partially because of the immunosuppressive action of sirolimus. Sirolimus can affect your ability to heal, to get vaccinations, and may increase the risk of developing certain cancers (such as skin cancers and lymphoma).