Study Design and Population A prospective, randomized, open label, blinded end-point (PROBE) pilot trial in pediatric kidney transplant recipients with non-dipping was conducted to determine the effect of chronotherapeutic alteration of anti-hypertensive medication on nocturnal BP. Non-dipper status was defined as \<10% decline in systolic or diastolic BP from daytime to nighttime on ABPM. Participants were required to have a minimum of one follow-up study visit in order to be included in the analysis. Participants were recruited from Cohen Children's Medical Center in New Hyde Park, New York and from the Children's Hospital of Philadelphia (CHOP) in Philadelphia, Pennsylvania from 2010 to 2018.

Intervention Participants randomized to the treatment group were assigned to receive a new anti-hypertensive medication in the evening (1 hour prior to bed time) in addition to their regular baseline medications. The intervention medication was enalapril, an angiotensin converting enzyme inhibitor (ACEi). If the participant was already on an ACEi or there was a contraindication to starting an ACEi (e.g. hyperkalemia, history of allergic reaction to ACEi), then isradipine was added instead. If the participant was already on an ACEi and calcium channel blocker at baseline, then propranolol was the new medication added. The choice of medications was made based on the pharmacokinetic profile of the medications (quick-onset and short to intermediate acting) to lower nocturnal BP with evening administration. The dose of the new medication was titrated up to the target dose if the medication was tolerated and there were no adverse events reported at the two-week visit. Participants in the new medication group were evaluated at 2 weeks, 6 weeks, 3 months and 6 months by the study team to assess for side effects. Participants started on an ACEi had serum electrolytes, BUN and creatinine, and a pregnancy test monitored at each study visit. Participants with side effects were switched to a different class of medication. Participants randomized to the control group continued to take their medications as usual. Participants in the control group were followed at baseline, 3 months and 6 months. No changes to other BP medications were allowed during the 6-month study period. Any participant who developed hypertensive daytime casual BP on repeated measurements was withdrawn from the study.

Randomization and Blinding Participants were randomized in a 1:1 ratio to intervention or control arms in parallel utilizing a blocked randomization strategy (in blocks of 2 and 4) in order to ensure similar numbers of participants in each arm. The randomization scheme was computer generated. Group assignments were concealed in sealed envelops and randomization allocation was done sequentially by a person not directly involved with the study. Interpretation of the outcome data (ABPM, echocardiograms, PWV, labs) was adjudicated by investigators blinded to the treatment group. Laboratory technicians and echocardiographers were blinded to the participant treatment group.

Study Procedures Cardiovascular Measures 24-hour ABPM, echocardiography and PWV were performed at baseline, 3 months and 6 months. Echocardiography was performed using 2-D echo in M-mode in accordance with the recommendations of the American Society of Echocardiography. The SphygmoCor Vx PWV system (AtCor Medical Pty Ltd, Australia) was used to measure the velocity of the BP waveform between the carotid artery and the radial artery. Two PWV readings were obtained and the average was used for analysis. A 22-item pediatric sleep questionnaire was administered to the parent/guardian of the study subject to identify subjects with sleep-related breathing disorders. This questionnaire has been validated and tested for reliability in predicting obstructive sleep apnea. The Treatment Satisfaction Questionnaire for Medications (TSQM) was administered to assess patient satisfaction with the change in treatment and the impact of the therapy on quality of life. The tool gathers information about effectiveness of medication, side effects, convenience and global satisfaction, rated from 0-100 for each parameter.

Statistical Analysis Descriptive statistics were used to characterize demographic and clinical measures in participants. Fisher's exact test and Student's t-test were used to compare baseline variables between the treatment and control groups. Student's t-tests were used to compare continuous ABPM variables (nocturnal dip percent, mean BP, BP load) between treatment and control groups at 3 and 6 months post-intervention. Fisher's exact test was conducted to compare the proportion of participants who changed dipper status and nocturnal hypertension status between the two groups at 3 and 6 months. Within-person changes in each group were examined using the paired Student's t-test and McNemar's test. Student's t-test or Wilcoxon Rank Sum test for non-normally distributed variables were used to compare values of delta LVMI and eGFR between groups at each time point and paired tests for within-person changes. Intention-to-treat analysis was done. Statistical analyses was done using SPSS 25 (IBM Inc.) statistical package. A p-value \< 0.05 was the criterion for statistical significance. For the primary outcome, the comparison of 14 subjects in each group provided 80% power (α = 0.05) to detect a 50% change from non-dipper status to dipper status in the treatment group compared to a 5% change in the control group. The study was not powered for analysis of secondary outcomes (LVMI, PWV, eGFR) as this was an exploratory aim for this pilot study.