[Therapeutic follow-up of cyclosporine. Main factors involved in the interpretation of results].

The therapeutic drug monitoring of cyclosporine (CsA) requires not only correct methodological conditions but also taking into consideration of numerous other factors involved in the value of blood drug concentrations. Main factors concern: the clinical state of patients. Liver function and bile flow act predominantly on drug clearance; the choice of monitoring parameters and of sampling time. Comparison was done of information given respectively by area under the curve and different sampling times. Usually blood concentration is monitored with trough level plus eventually another concentration measured 4-6 h after drug administration; the time-table. Blood concentrations are measured at steady-state period. Bioavailability of CsA increases in the immediate postoperative period after transplantation; ways of CsA administration. Trough level is influenced by dividing up of the daily dose. In case of continuous i.v. infusion mean blood concentration, but not trough concentration, is measured; drug interactions. Several drugs modify blood concentrations of CsA. Others induce an additive nephrotoxicity or immunosuppressive effect. Recommended blood trough concentrations vary with clinical indications, experience and therapeutic habits of each transplant center. Currently recommended values (CsA whole blood concentration determined by specific method) are 150-250 ng/ml in renal, heart, liver and bone marrow grafts, during the 3 months after transplantation, with good renal function. Concentrations are often higher for lung transplantation.