Adherence to, and patient convenience of, prolonged-release tacrolimus in stable kidney and liver transplant recipients after conversion from immediate-release tacrolimus in routine clinical practice in Switzerland
Authors: Bonani Marco , Balaphas Alexandre , Bedino Giulia , Bühler Léo , Dutkowski Philipp , Fausch Kathrin , Gluderer Silvia , Graf Nicole , Hirt-Minkowski Patricia , Müllhaupt Beat , Schönholzer Carlo , Schulz Martin MP , Venzin Reto , Wüthrich Rudolf P 
Published: February 2021

AIMS OF THE STUDY
Non-adherence to immunosuppressive therapy in patients following solid organ transplantation is associated with an increased risk of transplant rejection and graft loss. A high pill burden can adversely affect patients’ implementation of their treatment regimens and may lead to omitting doses of medication. The aim of this study was to investigate medication implementation adherence in liver and kidney transplant recipients converted from twice-daily, immediate-release tacrolimus to once-daily, prolonged-release tacrolimus.

METHODS
This multicentre, non-interventional, observational, 12-month study evaluated implementation adherence in routine practice at five hospitals in Switzerland. Patients attended four clinical visits: at baseline (pre-conversion), and then at week 2, month 6 and month 12 post-conversion. Implementation was defined as consistently taking medication at the correct time and at the correct dose in order to achieve target tacrolimus trough levels. Implementation adherence was evaluated in three ways: using the Basel Assessment of Adherence to Immunosuppressive Medications Scale (BAASIS) interview questionnaire (at baseline and month 12), investigator-rated patient adherence (recorded at all visits), and tacrolimus trough levels (assessed throughout the study; sub-therapeutic levels were predefined by the investigator on an individual patient basis, over-therapeutic levels were defined as tacrolimus trough levels >15 ng/ml). The primary composite endpoint was non-adherence according to the BAASIS at month 12, any post-conversion investigator adherence rating of “poor”, or sub-therapeutic or over-therapeutic tacrolimus trough levels at month 6 or 12. Secondary endpoints included: individual components of the composite non-adherence primary endpoint, tacrolimus pill burden, patient satisfaction, and adverse drug reactions.

RESULTS
Seventy-five patients received prolonged-release tacrolimus; 68 patients (46 kidney and 22 liver transplant recipients) completed the study. Of these 68 patients, 24 had missing data for at least one component of the primary endpoint; therefore, data for the primary composite endpoint were evaluable for 44 patients. Most (81.8%; 36/44) patients were non-adherent for the composite endpoint. Sub-therapeutic tacrolimus trough levels outside of the predefined therapeutic range were the largest contributor to the composite endpoint, and were detected in 62.0% (31/50) of patients. Overall non-adherence according to the BAASIS was similar pre-conversion (30.7%) and at 12 months post-conversion (28.3%). Investigators rated adherence as “poor” for two patients. Prolonged-release tacrolimus decreased tacrolimus pill burden in 66.7% of patients. All patients were very satisfied / satisfied with prolonged-release tacrolimus; 75.0% found it easier to remember to take prolonged-release versus immediate-release tacrolimus. Twenty percent of patients reported adverse drug reactions, with infections being the most frequently reported (9.3%).

CONCLUSION
Overall, 1-year non-adherence rates were similar following conversion from immediate-release to prolonged-release tacrolimus; however, prolonged-release tacrolimus intake was more convenient. No new safety signals were detected.