Optimization of Therapeutic Drug Monitoring for Tacrolimus and Mycophenolate in Pediatric Kidney Transplant Recipients: a PK/PD Study

The goal of this observational, pharmacokinetic study is to evaluate factors that change drug exposure in pediatric kidney transplant recipients so investigators can make better dosing decisions. The main question it aims to answer is:

Can investigators quantify the impact of factors that change with time (like food intake and medication adherence) on tacrolimus and mycophenolate? Our hypothesis is that inconsistent drug and food intake will increase day to day variability in drug exposure, and investigators can use this information to help us make decisions about what is the best dose.

Participants will participate in the study on 7 days over the course of 1 year. On day 1, participants will be asked questions to see if participants are able to be in this study. Investigators will ask what immunosuppression participants are taking, how tall and how much participants weigh.

On day 2, participants and their parent/guardian will be taught how to use the device to collect the blood samples and decide on which days to collect them.

On days 3-6, participants will collect blood samples 4 separate times over about 1 year. Collection days should try to be scheduled every 3 months (+/- 2 weeks).

On each collection day, participants will collect a sample 7 different times over 9 hours. Each collection will only take approximately 5 minutes. Participants will be asked to collect a blood sample immediately before the morning dose of tacrolimus or mycophenolate, and 20 min, 1hr, 3hr, 4hr, 6hr, 9hr after the dose.

Also on collection days, participants will receive text messages and be asked to complete different assessments about their medications, diet, and how they feel by responding to the texts.

On day 7, participants will have the opportunity to participate in an interview where investigators will ask about participants' experience in the study.