Serum tacrolimus measurement is used to monitor drug levels in the body during treatment to optimize immunosuppression, to monitor patients' compliance with treatment, and to evaluate any drug toxicity.
Tacrolimus (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 ingestion. His half-life in blood is 11.7 hours in patients with liver transplantation.
Tacrolimus is metabolised 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 (antipyretic) 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 balsam (St. John's wort)
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. 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.
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