Related Experiment Video
Updated: May 5, 2026

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
Flatter Tacrolimus Pharmacokinetic Profiles in Pediatric Kidney Transplant Recipients Receiving Liquid Formulations:
Sarah Lafond1, Mara Medeiros-Domingo2,3, Sara Henderson4
1London Health Sciences Centre, Children's Hospital, London, Ontario, Canada.
Background:
Compounded tacrolimus suspensions are frequently used in pediatric kidney transplant recipients who cannot reliably swallow capsules or who receive medication via a gastrostomy tube. Clinicians at our center observed unusually flat mini-pharmacokinetic (mini-PK) profiles in patients receiving liquid tacrolimus.
Methods:
We retrospectively analyzed 13 tacrolimus mini-PK profiles (C0, C1, C2, C4) from 7 pediatric kidney transplant recipients receiving compounded liquid tacrolimus, measured by LC-MS/MS in routine clinical care. As a contemporaneous comparator measured by the same assay, we assembled mini-PK profiles from pediatric recipients receiving capsule tacrolimus at our center (December 2024 onward). A historical capsule cohort from Berlin measured with Abbott Tacrolimus II immunoassay was used only as external context.
Results:
Contemporary LC-MS/MS capsule profiles showed the expected early post-dose rise, whereas liquid profiles remained comparatively flat across the 0-4 h window. In the historical capsule cohort, higher trough concentrations were associated with lower Cmax/Cmin ratios, consistent with a trough-dependent change in apparent PK shape.
Conclusions:
In this Quality Improvement (QI) analysis, pediatric patients receiving compounded liquid tacrolimus demonstrated flatter mini-PK profiles than contemporaneous capsule recipients when evaluated within the same analytical platform. These findings support closer attention to PK shape (not trough alone) in clinically complex children requiring liquid formulations and motivate prospective studies that control for gastrointestinal comorbidity, co-medications, and administration route.
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