Related Experiment Video
Updated: Jun 24, 2026

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
Tacrolimus variability and medication adherence pre- and post-conversion from immediate-release to extended-release
Leandra Bitterfeld1,2, Rachel L Jackson1, Jorge Sanchez-Garcia3,4
1Intermountain Primary Children's Hospital, Salt Lake City, Utah, USA.
Background:
Adolescents receiving solid organ transplants (SOT) are at increased risk for rejection and graft loss, driven by suboptimal immunosuppressive medication adherence. This study evaluated the effect of conversion from immediate-release tacrolimus (IR-Tac) to extended-release tacrolimus (LCPT) on medication adherence in pediatric SOT recipients.
Methods:
We conducted a retrospective, observational single-center study of heart, liver, and kidney transplant recipients who converted from IR-Tac to LCPT. Medication adherence was measured as tacrolimus standard deviation (tac-SD), with tac-SD > 2 considered the threshold for poor adherence, and self-reported adherence during the one year before and after conversion.
Results:
Fifty-four pediatric SOT recipients were included, with a median age of 9 years at transplant and 14.4 years at conversion from IR-Tac to LCPT. Among the entire cohort, overall tac-SD did not differ before and after conversion. Among children with high baseline variability (tac-SD > 2), tac-SD significantly decreased from a median of 3.0 to 2.7 (p = 0.014), whereas children with low baseline variability (tac-SD < 2) experienced a significant increase in tac-SD from 1.3 to 2.2 (p < 0.001). The proportion of children reporting missed doses more than once a week decreased from 13 (24%) to 7 (13%; p = 0.07). There was no change in tac-SD between children who were and were not converted to LCPT for an adherence concern.
Conclusion:
Tac-SD decreased after conversion from IR-Tac to LCPT among those with high baseline variability but increased among those with low baseline variability; there were no significant changes in subjective adherence measures. The effectiveness of conversion from IR-Tac to LCPT for adherence is unclear.
Related Concept Videos
Pharmacokinetics in Pediatric Patients: Overview and Drug Absorption
Pharmacokinetics in Pediatric Patients: Drug Excretion
Pharmacokinetics in Pediatric Patients: Drug Metabolism
Drug Accumulation During Multiple Dosing: Intermittent IV Infusions
IV Infusion to Oral Dosing: Conversion Methods
Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase
