Immunosuppression Adherence in Stable Kidney Transplant Patients Converted From Immediate- to Prolonged-Release Tacrolimus in Clinical Practice: A Norwegian Study

BACKGROUND: This study investigated medication adherence in kidney transplant patients (KTPs) converted from immediate-release tacrolimus (IR-T) to prolonged-release tacrolimus (PR-T)-based immunosuppression in routine practice. METHODS: Noninterventional, observational, multicenter study in Norway. Included adult KTPs with stable graft function, converted from IR-T (baseline) to PR-T (1 mg:1 mg) in routine practice. Data were collected at baseline, and months 1, 3, 6, and 12 postconversion. Primary endpoint: adherence using the Basel Assessment of Adherence to Immunosuppressive Medication Scale. Secondary assessments: tacrolimus dose and trough levels (target, 3-7 ng/mL), clinical laboratory parameters (eg, estimated glomerular filtration rate [Modified Diet in Renal Disease]), and adverse events. RESULTS: Ninety-one KTPs (mean ± SD age 47.7 ± 14.3 years) were analyzed. Mean ± SD change in PR-T dose from baseline (4.4 ± 2.4 mg/d) to month 12 was −0.1 ± 0.9 mg/d; mean tacrolimus trough levels remained within target. Overall medication adherence increased from 45.6% at baseline to 58.1% at month 1, but was similar to baseline thereafter; taking and timing adherence followed a similar pattern. Odds ratio (OR) for adherence at month 1 (but not at other time points) was greater versus baseline for overall (OR, 1.71; P = 0.0205), taking (OR, 3.38; P = 0.0004), and timing (OR, 1.77, P = 0.0252) dimensions. Mean ± SD Basel Assessment of Adherence to Immunosuppressive Medication Scale visual analogue scale score at baseline was 96.4 ± 5.5%, and increased postconversion. Estimated glomerular filtration rate remained stable (month 12, 61.6 ± 17.7 mL/min per 1.73 m(2)), as did other laboratory parameters. Two (2.2%) patients had adverse events considered probably/possibly treatment-related. CONCLUSIONS: There was disparity between high, patient-perceived and low, actual adherence. Converting stable KTPs from IR-T to PR-T in routine practice did not impact long-term adherence to immunosuppression; renal function remained stable.