Continuous versus intermittent tacrolimus for graft-versus-host disease prophylaxis in pediatric hematopoietic stem cell transplantation patients (Tic Tac).

Background: Tacrolimus is administered via a continuous or intermittent IV infusion to prevent acute graft versus host disease (aGvHD) in pediatric hematopoietic stem cell transplant (HSCT) recipients. Limited comparison data is available.

Objectives: The primary objective was to compare the proportion of therapeutic tacrolimus trough levels in the first 30 days post-stem cell infusion. Secondary outcomes were prevalence of aGvHD, intra-patient variability (IPV) and safety.

Study Design: This was a retrospective cohort study that included pediatric HSCT recipients between March 1, 2015 and October 31,2021 at BC Childrens Hospital. Adverse events were assessed using the Naranjo scoring tool.

Results: Overall, 60 transplants in 59 patients were included; n = 36 intermittent IV and n = 24 continuous IV. Median proportion of blood levels (intermittent and continuous) within 8-12 ug/L was 38% and 56%, respectively (p = 0.04). IPV was 33% and 31% and aGvHD was 39% and 38% in intermittent and continuous respectively. There was a higher proportion of adverse effects in the intermittent group with the exception of hypomagnesemia.

Conclusions: Continuous IV tacrolimus provided a higher proportion of levels within therapeutic range. Neither achieved therapeutic trough levels in more than 56% of transplants. However, there was large intra-patient variability in both groups.