Tacrolimus measurement in the blood is used to monitor drug levels during treatment to optimize immunosuppression, monitor patients' compliance with treatment, and evaluate any drug toxicity.
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Tacrolimus (Prograf), formerly known as FK506, is an immunosuppressive drug derived from the bacterium Streptomyces tsulenbaensis. It has been shown to be effective in treating graft rejection in liver and kidney transplants. Tacrolimus inhibits T-cell activation by inhibiting calcineurin phosphatase activity, although its precise mechanism of action is not fully known. Tacrolimus is also linked to plasma proteins and to a large extent to erythrocytes. The drug can be administered intravenously or orally. Its absorption from the gastrointestinal tract is variable and irregular. Its peak blood concentrations are reached within 1.5 to 3.5 hours after administration. Its half-life in blood is 11.7 hours in patients with liver transplantation.
Tacrolimus is metabolized by the enzyme CYP3A4 and therefore its concentrations are affected by drugs that inhibit (calcium channel blockers, antifungal agents, certain antibiotics, grapefruit juice), or stimulate (anticonvulsants, rifampicin) this enzyme. Tacrolimus can cause nephrotoxicity, especially when used in high doses. It should be used with caution when used in combination with other immunosuppressive drugs, in particular cyclosporin.
- Medications that may increase tacrolimus levels are: Diltiazem, verapamil, clotrimazole, fluconazole, ketoconazole, voriconazole, clarithromycin, erythromycin, nelfinavir, ritonavir
- Medications that can reduce tacrolimus levels are: Rifampicin, phenytoin, carbamazepine, phenobarbital, octreotide, and St. John's wort
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
