Abstract
Tacrolimus, a novel macrocyclic lactone with immunosuppressive properties, is currently administered as an intravenous formulation, and as capsules for oral use are available, although other formulations are investigated. Tacrolimus concentrations in biological fluids were measured using a number of methods that are evaluated and compared in this article. The development of a simple, specific and sensitive assay method for measuring the concentrations of tacrolimus with the low absorptivity of the drug, plasma and blood low concentrations, and the presence of metabolites and other medications that may interfere with the determination of tacrolimus concentrations limited . Currently, most of the pharmacokinetic data on tacrolimus on an enzyme-linked immunosorbent assay method, which does not distinguish tacrolimus from related metabolites. The rate of absorption of tacrolimus is variable, with peak blood or plasma concentrations achieved in 0.5 to 6 hours, is about 25% of the oral dose bioavailable. Tacrolimus is extensively bound to red blood cells, appear with an average blood-plasma ratio of about 15, albumin and alpha 1-acid glycoprotein bind mainly tacrolimus in plasma. Tacrolimus is completely metabolized prior to excretion. The mean half-life is 12 hours and the total clearance based on blood concentration of approximately 0.06 l / h / kg. The elimination of tacrolimus in the presence of liver function and in the presence of various drugs reduced. Several factors contribute to the large inter-and interindividual variability in the pharmacokinetics of tacrolimus are reviewed here. Because of this variability, the narrow therapeutic range of tacrolimus and the potential for multiple interactions with other drugs, the monitoring of tacrolimus blood levels is useful for optimization of therapy and dosage design.
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