Biological and psychological differences in the child and adolescent transplant recipient.

Solid organ transplantation has become accepted therapy for the treatment of end-stage organ dysfunction in children. As early management of the pediatric transplant recipient has improved, important age-related differences in long-term patient outcomes have become apparent. Late morbidity and mortality can, in most cases, be attributed to the consequences of long-term immunosuppression: graft loss from under-immunosuppression or an increased incidence of cancer, hypertension, renal failure or diabetes from over-immunosuppression. Age-related differences in both biological and psychological factors play an important role in the optimization of therapy in the transplanted child. Important age-related differences have been demonstrated in all phases of pharmacokinetics: absorption, distribution, metabolism and elimination. Information regarding specific age-related pharmacokinetic differences is lacking for many immunosuppressive medications. Further study using physiologically based pharmacokinetic (PBPK) models will lead to more specific recommendations for age-based immunosuppression protocols. Non-adherence is common among solid organ transplant recipients of all ages and the consequences of non-adherence include increased rejection, late graft loss and death. The biological and psychological developmental changes that occur during adolescence place the transplanted adolescent at an even higher risk of non-adherence and poor outcome than other age groups. Further studies to elucidate the importance of both age-related pharmacokinetic and behavioral factors are needed to formulate therapeutic interventions that would improve adherence and patient outcomes.