Pharmacokinetics of tacrolimus in the first days after heart and lung transplantation.

Summary:

Tacrolimus is an immunosuppressive agent used as prophylaxis for organ rejection in lung, heart, liver and kidney transplantation. In previous studies, high inter- and intra-individual variability in tacrolimus blood concentration has been observed among transplant recipients. The range and the factors explaining variation in tacrolimus blood concentrations during the first days post-transplantation in heart and lung transplant recipients are largely unknown. More insight on factors causing the inter- and intra-individual variability in tacrolimus concentrations is necessary in order to adapt dose regimen to individuals. Individualization of dosing regimen is needed to prevent organ toxicity, if tacrolimus concentration is too high, and organ rejection, if tacrolimus concentration is too low or in other words, to improve safety of tacrolimus and minimize toxicity directly after heart and lung transplantation.



Objectives:

Primary objective:

To show that the variability of whole blood total and unbound plasma tacrolimus concentrations during the first 6 days post transplantation is larger than the variation of tacrolimus concentrations in stable clinical situation.

Secondary objectives:

1. To show that unbound tacrolimus plasma concentrations can better predict the occurrence of renal dysfunction than whole blood total tacrolimus concentrations;

2. Identification of variables influencing the unbound tacrolimus plasma concentrations;

3. To evaluate whether variations in tacrolimus concentrations in the first days after lung transplantation in cystic fibrosis patients are higher than without cystic fibrosis.

Long-term objective:

1. The data will be used to develop a kinetic model in the future in order to dose tacrolimus more accurately to prevent adverse effects of tacrolimus.



Design:

We will perform a multiple doses, open-label, observational, prospective and multi-center study in heart and lung transplant recipients.



Population:

Heart and lung transplant recipients admitted to the Intensive Care of a University Medical Center in the first six days post transplantation.



Procedures:

Patients will be included at the outpatient’s department before the transplantation. Tacrolimus will be administered orally twice a day, according to the usual procedure of the Intensive Care Center. Blood and urine will be collected. Presence or absence of cystic fibrosis will be recorded among lung transplant recipients. Concomitant drugs as a cause of kidney dysfunction will be recorded and plasma concentrations will be measured at steady state. Renal function will also be evaluated in a later phase in de outpatient department after circa 1, 3 and 6 months.

More insight on factors causing the inter- and intra-individual variability in tacrolimus concentrations is necessary in order to improve safety of tacrolimus and minimize toxicity directly after heart and lung transplantation.

Pharmacokinetic parameters will be observed in 30 heart and lung transplant recipients up to the first 6 days after transplantation or shorter if patients are discharged from the intensive care earlier. Renal function will be evaluated in the first days and circa 1, 3 and 6 months after transplantation in the out-patient department.

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