Herbal Spotlight
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NEW WARNING
Wyeth Pharmaceuticals issued a "Dear Health Care Professional" letter about important changes to the prescribing information for sirolimus (Rapamune), a drug prescribed to prevent organ rejection in patients age 13 and older. The change to prescribing information concerns therapeutic monitoring for the drug. The recommended reference test to determine sirolimus trough levels is high-performance liquid chromatography (HPLC). Several immunoassays have also been developed to allow for quick turnaround of results. Wyeth recently became aware that one of the most commonly used immunoassay platforms, IMx, may sometimes give inadequate results. This may vary from one laboratory to another and may also be affected by the type of blood samples (fresh or frozen) used. Therefore switching between platforms can produce differing results that may be clinically significant.
The prescribing information has been changed to read: "Since sirolimus trough results are assay and laboratory dependent, and the results may change over time, adjustment to the targeted therapeutic range must be made with a detailed knowledge of the site-specific assay used."
Wyeth advises health care providers to determine:
- which assay is being used in their laboratories
- whether there's been any change to the assay used
- whether there were any reference range changes.
By keeping informed, health care providers can appropriately change target levels to achieve optimal clinical outcomes.
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sirolimus