Everolimus (VOTUBIA®, AFINITOR®, CERTICAN®, ZORTRESS®) is an immunosuppressant and anticancer drug that inhibits the mechanistic target of rapamycin (mTOR), a kinase involved in regulating cell growth, proliferation, motility, survival, and protein synthesis. By blocking mTOR, everolimus reduces the proliferation of cells, making it useful in the treatment of various cancers, including renal cell carcinoma, breast cancer, and neuroendocrine tumors. It is also used in organ transplantation to prevent graft rejection by suppressing the immune system. Everolimus is typically administered orally and is often prescribed in combination with other chemotherapy or immunosuppressive agents. The Everolimus blood test measures the concentration of the drug in the bloodstream to ensure that therapeutic levels are maintained, minimizing the risk of side effects while optimizing treatment efficacy.
Everolimus has a narrow therapeutic window, meaning that minor variations in its concentration can lead to significant changes in drug effectiveness and safety. Monitoring blood levels is particularly important in patients undergoing treatment for cancer or those who have received organ transplants, where precise dosing is critical to balance the risk of cancer progression or graft rejection with the potential for side effects such as immunosuppression, infections, or organ damage. The target therapeutic range for everolimus typically falls between 3-15 ng/mL, but individual patients may require different targets based on their specific clinical circumstances.
The liver primarily metabolizes Everolimus through the cytochrome P450 enzyme system, particularly CYP3A4. Therefore, drug interactions, especially with medications that influence CYP3A4 activity, can significantly impact everolimus levels. For example, inhibitors of this enzyme, such as certain antifungals, antibiotics, or protease inhibitors, can increase everolimus concentrations. In contrast, inducers like certain anticonvulsants or herbal supplements like St. John's Wort can lower its levels. Monitoring everolimus levels is critical in these cases to prevent adverse effects like nephrotoxicity, thrombocytopenia, or mucositis and to ensure the drug's effectiveness in preventing tumor growth or organ rejection.
The test is also essential in patients with impaired liver or kidney function, as these conditions can affect the drug's metabolism and clearance, leading to drug accumulation or suboptimal levels. For patients with liver disease, reduced metabolic clearance may necessitate dose adjustments. In contrast, in patients with kidney impairment, the excretion of everolimus could be delayed, requiring close monitoring of blood levels to prevent toxicity.
