Assessment of tacrolimus intrapatient variability in stable adherent transplant recipients: Establishing baseline values

Impact of intra-patient variability of tacrolimus on allograft function and CD4 + /CD8 + ratio in kidney transplant recipients: a retrospective single-center study

BACKGROUND

Tacrolimus is a critical component of immunosuppressive therapy for kidney transplant recipients. Intra-patient variation (IPV) of tacrolimus levels affects the function of transplanted kidney.

AIM

This study aimed to investigate the impact of tacrolimus IPV on kidney function, examine its association with post-transplant duration, and assess its effect on the immune status of transplant recipients.

METHOD

This retrospective study was conducted from January 2016 to February 2022. IPV was evaluated using the coefficient of variation (CV) of tacrolimus trough levels from 6 to 48 months after transplantation. Patients were divided into low- and high-IPV groups based on the median CV. Significant differences in kidney function, CD4 + /CD8 + ratio, and post-transplant duration between these groups were analyzed.

RESULTS

Among 189 patients, tacrolimus IPV showed a strong correlation with serum creatinine clearance rate (Ccr) and estimated glomerular filtration rate (eGFR) (p < 0.05). Tacrolimus IPV was significantly correlated with post-transplant duration in only two patients (p < 0.05). Using a median CV of 15.4% to categorize patients, the high IPV group, compared to the low IPV group, exhibited significantly higher eGFR at 6-9 months (p < 0.05), lower Ccr at 9-12 months (p < 0.05), and reduced Ccr and eGFR at 15-18 months (p < 0.05). Six months after transplantation, the high IPV group had a significantly lower CD4 + /CD8 + ratio than the low IPV group (p < 0.05).

CONCLUSION

This study highlights the significant impact of tacrolimus IPV on transplant kidney function and immune status in transplant patients at various post-transplantation intervals.

A Feasibility Open-Labeled Clinical Trial Using a Second-Generation Artificial-Intelligence-Based Therapeutic Regimen in Patients with Gaucher Disease Treated with Enzyme Replacement Therapy

Background/Objectives: Gaucher Disease type 1 (GD1) is a recessively inherited lysosomal storage disorder caused by a deficiency in the enzyme β-glucocerebrosidase. Enzyme replacement therapy (ERT) has become the standard of care for patients with GD. However, over 10% of patients experience an incomplete response or partial loss of response to ERT, necessitating the exploration of alternative approaches to enhance treatment outcomes. The present feasibility study aimed to determine the feasibility of using a second-generation artificial intelligence (AI) system that introduces variability into dosing regimens for ERT to improve the response to treatment and potentially overcome the partial loss of response to the enzyme. Methods: This was an open-label, prospective, single-center proof-of-concept study. Five patients with GD1 who received ERT were enrolled. The study used the Altus Care™ cellular-phone-based application, which incorporated an algorithm-based approach to offer random dosing regimens within a pre-defined range set by the physician. The app enabled personalized therapeutic regimens with variations in dosages and administration times. Results: The second-generation AI-based personalized regimen was associated with stable responses to ERT in patients with GD1. The SF-36 quality of life scores improved in one patient, and the sense of change in health improved in two; platelet levels increased in two patients, and hemoglobin remained stable. The system demonstrated a high engagement rate among patients and caregivers, showing compliance with the treatment regimen. Conclusions: This feasibility study highlights the potential of using variability-based regimens to enhance ERT effectiveness in GD and calls for further and longer trials to validate these findings.

The Influence of Tacrolimus Exposure and Metabolism on the Outcomes of Kidney Transplants

Tacrolimus (TAC) has a narrow therapeutic window and patient-specific pharmacokinetic variability. In our study, we analyzed the association between TAC exposure, metabolism, and kidney graft outcomes (function, rejection, and histological lesions). TAC trough (C0), coefficient of variation (TAC CV), concentration/dose ratio (C/D), and biomarkers related to kidney injury molecule-1 (KIM-1) and neutrophil gelatinase lipocalin (NGAL) were analyzed. We examined 174 patients who were subjected to a triple immunosuppressive regimen and underwent kidney transplantation between 2017 and 2022. Surveillance biopsies were performed at the time of kidney implantation and at three and twelve months after transplantation. We classified patients based on their Tac C/D ratios, classifying them as fast (C/D ratio < 1.05 ng/mL × 1/mg) or slow (C/D ratio ≥ 1.05 ng/mL × 1/mg) metabolizers. TAC exposure/metabolism did not significantly correlate with interstitial fibrosis/tubular atrophy (IF/TA) progression during the first year after kidney transplantation. TAC CV third tertile was associated with a higher chronicity score at one-year biopsy. TAC C/D ratio at three months and Tac C0 at six months were associated with rejection during the first year after transplantation. A fast TAC metabolism at six months was associated with reduced kidney graft function one year (OR: 2.141, 95% CI: 1.044-4.389, p = 0.038) and two years after transplantation (OR: 4.654, 95% CI: 1.197-18.097, p = 0.026), and TAC CV was associated with reduced eGFR at three years. uNGAL correlated with IF/TA and chronicity scores at three months and negatively correlated with TAC C0 and C/D at three months and one year. Conclusion: Calculating the C/D ratio at three and six months after transplantation may help to identify patients at risk of suffering acute rejection and deterioration of graft function.

Utility of Routine Post Kidney Transplant Anti-HLA Antibody Screening

Introduction

De novo donor-specific antibody (dnDSA) is a strong biomarker associated with the development of antibody-mediated rejection (AMR) and graft loss after kidney transplantation. This procedure is expensive; however, systematic annual screening was recommended by some national organ transplant agencies or societies even though its clinical utility was not clearly established.

Methods

To address this question, we retrospectively assessed the incidence of dnDSA according to the test justification (clinically indicated or systematic) in a cohort of low-immunological risk patients, defined by being nonhuman leukocyte antigen (non-HLA)-sensitized and having no previous kidney transplants.

Results

A total of 1072 patients, for whom 4611 anti-HLA tests were performed, were included in the study. During the follow-up period of 8 (interquartile range, IQR: 5-11) years, 77 recipients developed dnDSA (prevalence of 7.2%). Thirty-five of these dnDSAs (45.5%) were detected during the first year posttransplantation. In 95% of patients with dnDSA, an immunizing event was identified in their medical records. dnDSA was detected in 46 of 4267 systematic screening tests (1.08%) performed. Active and chronic AMR were frequently observed in biopsies performed after systematic DSA testing (17.9% and 15.4%, respectively).

Conclusion

Our results suggest that the detection by systematic screening of dnDSA in low-immunological risk kidney transplant patients without sensitizing events is a rare event, especially after 1 year. Moreover, in real life, systematic annual screening for dnDSA, seems having a limited impact to detect AMR at an earlier stage compared to patients in whom dnDSA was detected after a clinically indicated test.

Exploratory associations of tacrolimus exposure and clinical outcomes after lung transplantation: A retrospective, single center experience

PURPOSE

This study aimed to investigate the potential impact of tacrolimus (TAC) exposure on clinical outcomes after lung transplantation.

METHODS

This retrospective observational study enrolled a total of 228 lung transplant recipients. TAC trough levels (C0) were collected for 3 intervals: 0-3 months, 3-12 months, and 12-24 months. The intra-patient variability (IPV) was calculated using coefficient of variation. Genotyping of CYP3A5*3 (rs776746) was performed. Patients were further divided into groups based on the C0 cut-off value of 8 ng/mL and IPV cut-off value of 30%. Cox proportional hazards regression models were used to explore the potential impact of C0 and IPV on outcomes of interests, including de-novo donor-specific antibodies (dnDSA), chronic lung allograft dysfunction (CLAD) and mortality.

RESULTS

The influence of CYP3A5*3 polymorphism was only significant for C0 and IPV during the first 3 months. Low C0 (< 8 ng/mL) at 3-12 months increased the risk of dnDSA (hazard ratio [HR] 2.696, 95% confidence interval [CI] 1.046-6.953) and mortality (HR 2.531, 95% CI 1.368-4.685), while High IPV (≥ 30%) during this period was associated with an increased risk of mortality (HR 2.543, 95% CI 1.336-4.839). Patients with Low C0/High IPV combination had significantly higher risks for dnDSA (HR 4.381, 95% CI 1.279-15.008) and survival (HR 6.179, 95% CI 2.598-14.698), surpassing the predictive power provided by C0 or IPV alone.

CONCLUSION

A combination of Low C0/High IPV might be considered in categorizing patients towards risk of adverse clinical outcomes following lung transplantation.

A Systematic Literature Review on the Use of Dried Biofluid Microsampling in Patients With Kidney Disease

BACKGROUND

Kidney disease is fairly unique due to the lack of symptoms associated with disease activity, and it is therefore dependent on biological monitoring. Dried biofluids, particularly dried capillary blood spots, are an accessible, easy-to-use technology that have seen increased utility in basic science research over the past decade. However, their use is yet to reach the kidney patient population clinically or in large-scale discovery science initiatives. The aim of this study was to systematically evaluate the existing literature surrounding the use of dried biofluids in kidney research.

METHODS

A systematic literature review was conducted using three search engines and a predefined search term strategy. Results were summarised according to the collection method, type of biofluid, application to kidney disease, cost, sample stability and patient acceptability.

RESULTS

In total, 404 studies were identified and 67 were eligible. In total, 34,739 patients were recruited to these studies with a skew towards male participants (> 73%). The majority of samples were blood, which was used either for monitoring anti-rejection immunosuppressive drug concentrations or for kidney function. Dried biofluids offered significant cost savings to the patient and healthcare service. The majority of patients preferred home microsampling when compared to conventional monitoring.

CONCLUSION

There is an unmet need in bringing dried microsampling technology to advance kidney disease despite its advantages. This technology provides an opportunity to upscale patient recruitment and longitudinal sampling, enhance vein preservation and overcome participation bias in research.

Implementing a self-reported immunosuppression adherence questionnaire to screen for non-adherence in routine care of kidney transplant recipients

INTRODUCTION

Self-reported measures of immunosuppression adherence have been largely examined in research settings.

METHODS

In this single center study of 610 kidney transplant recipients, we examined if a voluntary, non-anonymous self-report measure could identify non-adherence in a routine clinic setting and how patients perceived such a measure. Non-adherence was measured using the Basel Assessment of Adherence to Immunosuppressive Medications Scale (BAASIS) and patient perception was elicited using a customized questionnaire.

RESULTS

Non-responders to the survey (15%) were younger, more likely to be black, and less likely to have had a pre-emptive transplant. Among complete responders (n = 485), 38% reported non-adherence with non-adherent patients being younger (54 y vs. 60 y; p = .01), less likely to have been on dialysis pre-transplant (59% vs. 68%; p = .04), further out from transplant (37 vs. 22 months; p < .001) and had more rejections in the preceding year (8% vs. 3%; p = .02). Self-reported non-adherence was associated with higher calcineurin inhibitor intra-patient variability (27.4% vs. 24.5%; p = .02), but not with donor-specific antibody detection (27.8% vs. 21.2%, p = .15). Of patients providing feedback (n = 500), the majority of patients felt comfortable reporting adherence (92%), that the survey was relevant to their visit (71%), and that the survey did not interfere with their clinic visit (88%).

CONCLUSION

In summary, a self-reported questionnaire during clinic visits identified immunosuppression non-adherence in a significant proportion of patients and was well received by patients. Integrating self-report measures into routine post-transplant care may enable early identification of non-adherence.

An individual segmented trajectory approach for identifying opioid use patterns using longitudinal dispensing data

PURPOSE

The aim of this study is to use electronic opioid dispensing data to develop an individual segmented trajectory approach for identifying opioid use patterns. The resulting opioid use patterns can be used for examining the association between opioid use and drug overdose.

METHODS

We retrospectively assembled a cohort of members on long-term opioid therapy (LTOT) between January 1, 2006 and June 30, 2019 who were 18 years and older and enrolled in one of three health care systems in the US. We have developed an individual segmented trajectory analysis for identifying various opioid use patterns by scanning over the follow-up and finding distinct opioid use patterns based on variability measured with coefficient of variation and trends of milligram morphine equivalents levels.

RESULTS

Among 31, 865 members who were on LTOT between January 1, 2006 and June 30, 2019, 58.3% were female, and the average age was 55.4 years (STD = 15.4). The study population had 152 557 person-years of follow-up, with an average follow-up of 4.4 years per enrollment per person (STD = 3.4). This novel approach identified up to 13 distinct patterns including 88 756 episodes of "stable" pattern (42.1%) with an average follow-up of 11.2 months, 29 140 episodes of "increasing" pattern (13.8%) with an average follow-up of 6.0 months, 13 201 episodes of ≤10% dose reduction (6.3%) with an average follow-up of 10.4 months, 7286 episodes of 11%-20% dose reduction (3.5%) with an average follow-up of 5.3 months, 4457 episodes of 21%-30% dose reduction (2.1%) with an average follow-up of 4.0 months, and 9903 episodes of >30% dose reduction (4.7%) with an average follow-up of 2.6 months.

CONCLUSIONS

A novel approach was developed to identify 13 distinct opioid use patterns using each individual's longitudinal dispensing data and these patterns can be used in examining overdose risk during the time that these patterns are ongoing.

Cumulative exposure to tacrolimus during early period after liver transplantation does not affect the recurrence of hepatocellular carcinoma

The clinical effects of tacrolimus (TAC) exposure on hepatocellular carcinoma (HCC) recurrence after liver transplantation (LT) remain unclear. In this retrospective single centric study, 512 patients who underwent LT for HCC were divided into four groups according to cumulative exposure to tacrolimus (CET) during 3 months after LT: conventional (n = 218), aggressive minimization (n = 32), minimization (n = 161), and high exposure (n = 101). Impact of CET on HCC recurrence and death were analyzed. Compared with the conventional group, the other three CET groups showed a similar risk of HCC recurrence. The aggressive minimization group showed a higher risk [hazard ratio (HR) 5.64, P < 0.001] and the high exposure group showed a marginal risk (HR 1.67, P = 0.081) of overall death compared to the conventional group. CET during 3 months was not associated with HCC recurrence in the matched cohort and various subgroups. TAC minimization is not effective to prevent HCC recurrence but could result in higher mortality in LT recipients.

Retrospective evaluation of LCP-tacrolimus (Envarsus XR) dosing in de novo kidney transplant

INTRODUCTION

Tacrolimus is known to exhibit significant inter- and intra-patient pharmacokinetic (PK) and pharmacodynamic (PD) variability regarding therapeutic response. LCP-tacrolimus (LCPT-Envarsus XR) was approved in 2018 for use as a de novo immunosuppressive agent in kidney transplants, but there is limited evidence to guide de novo dosing of LCPT in patients with obesity. The primary objective of this study was to evaluate the impact of different calculated weight-based de novo LCPT dosing on early transplant outcomes.

METHODS

This was a retrospective study of patients with obesity (BMI ≥ 30 kg/m2 ) who received a kidney transplant at the University of Illinois Hospital and Health System (UIH), between March 2019 and March 2021. Subjects were included if were age 18 years or older and received de novo LCPT throughout index hospitalization. The primary endpoint of this study was to compare correlations between the first tacrolimus trough level and dosing weight strategy (e.g., TBW, AdjBW, IBW).

RESULTS

There was a statistically significant, though modest, correlation between all three dosing strategies and the first tacrolimus trough level (TBW correlation coefficient = .431, p < .001; AdjBW correlation coefficient = .455, p < .001; IBW correlation coefficient = .465; p < .001). In regression modeling for supratherapeutic levels each additional .01 mg/kg increase in dose by TBW, AdjBW, and IBW increased the odds of a supratherapeutic level by 1.46, 1.34, and 1.24, respectively (p < .001).

CONCLUSIONS

The use of LCPT in kidney transplant recipients with obesity dosed using TBW demonstrated the strongest correlation with initial supratherapeutic tacrolimus levels. Larger prospective studies are needed to investigate the further impact of body weight on dosing regimens in the obese population.

Optimizing medication adherence with home-monitoring - A feasibility study using capillary microsampling and mHealth in solid organ-transplanted adolescents

BACKGROUND

Reliable methods to detect and reduce medication nonadherence in solid organ-transplanted (SOT) adolescents are warranted. We aimed to evaluate the feasibility of combining a medication-manager application (TusenTac®-app) with home-sampling of tacrolimus (Tac) in young SOT recipients.

METHODS

Kidney and combined SOT recipients between 14 and 25 years were included. During an 8-week intervention period, the participants were instructed to use the transplant-specific, age-adapted TusenTac®-app daily and to perform weekly at-home Tac trough finger-prick microsampling. Microsample Tac concentrations were controlled against timed venous samples twice. Medication implementation and persistence adherence were measured with BAASIS© questionnaires, TusenTac®-registrations, Tac trough concentration coefficient of variation (CV%) and self-reporting by interview. For comparison, venous Tac trough CV% were obtained from the year before and after the short-term intervention.

RESULTS

Twenty-two recipients were included, two withdrawals, leaving 20; median age 17.9 (14.5-24.8) years, 12 females (60%). The participants registered their dosage intake 88% (1502/1703) of the expected times, and 90% (106/118) of the microsamples were obtained correctly. At inclusion, 11 recipients (55%) were nonadherent assessed with BAASIS© questionnaire, four of these (36%) turned adherent during the intervention period. At the end, 70% reported improved timing-adherence at the interview. There was no significant change in TacCV% from the year before to the year after the short-term intervention. Home-sampling was reliable and measured Tac concentrations accurately.

CONCLUSIONS

Home-monitoring, combining Tac finger-prick microsampling and a medication-manager app, is feasible in adolescent SOT recipients with 70% perceived improvement in medication timing-adherence. There were no significant long-term changes in TacCV% confirming the need for continuous use and individualized interventions.

Patient randomised controlled trial of technology enabled strategies to promote treatment adherence in liver transplantation: rationale and design of the TEST trial

BACKGROUND AND AIMS

Liver transplantation is a life-saving procedure for end-stage liver disease. However, post-transplant medication regimens are complex and non-adherence is common. Post-transplant medication non-adherence is associated with graft rejection, which can have long-term adverse consequences. Transplant centres are equipped with clinical staff that monitor patients post-transplant; however, digital health tools and proactive immunosuppression adherence monitoring has potential to improve outcomes.

METHODS AND ANALYSIS

This is a patient-randomised prospective clinical trial at three transplant centres in the Northeast, Midwest and South to investigate the effects of a remotely administered adherence programme compared with usual care. The programme monitors potential non-adherence largely levering text message prompts and phenotypes the nature of the non-adhere as cognitive, psychological, medical, social or economic. Additional reminders for medications, clinical appointments and routine self-management support are incorporated to promote adherence to the entire medical regimen. The primary study outcome is medication adherence via 24-hour recall; secondary outcomes include additional medication adherence (ASK-12 self-reported scale, regimen knowledge scales, tacrolimus values), quality of life, functional health status and clinical outcomes (eg, days hospitalised). Study implementation, acceptability, feasibility, costs and potential cost-effectiveness will also be evaluated.

ETHICS AND DISSEMINATION

The University of Pennsylvania Review Board has approved the study as the single IRB of record (protocol # 849575, V.1.4). Results will be published in peer-reviewed journals and summaries will be provided to study funders.

TRIAL REGISTRATION NUMBER

NCT05260268.

Impact of tacrolimus intra-patient variability in adverse outcomes after organ transplantation

Tacrolimus (Tac) is currently the most common calcineurin-inhibitor employed in solid organ transplantation. High intra-patient variability (IPV) of Tac (Tac IPV) has been associated with an increased risk of immune-mediated rejection and poor outcomes after kidney transplantation. Few data are available concerning the impact of high Tac IPV in non-kidney transplants. However, even in kidney transplantation, there is still a controversy whether high Tac IPV is indeed detrimental in respect to graft and/or patient survival. This may be due to different methods employed to evaluate IPV and distinct time frames adopted to assess graft and patient survival in those reports published up to now in the literature. Little is also known about the influence of high Tac IPV in the development of other untoward adverse events, update of the current knowledge regarding the impact of Tac IPV in different outcomes following kidney, liver, heart, lung, and pancreas tran splantation to better evaluate its use in clinical practice.

Feasibility of a positive psychology intervention (PATH) in allogeneic hematopoietic stem cell transplantation survivors: Randomized pilot trial design and methods

BACKGROUND

Although patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) experience low levels of positive psychological well-being (PPWB), interventions that specifically boost PPWB in this population are lacking.

OBJECTIVE

To describe the methods of a randomized controlled trial (RCT) designed to assess the feasibility, acceptability, and preliminary efficacy of a positive psychology intervention (PATH) tailored to the unique needs of HSCT survivors and aimed to decrease anxiety and depression symptoms and boost quality of life (QOL).

METHODS

We will conduct a single-institution RCT of a novel nine-week phone-delivered manualized positive psychology intervention compared to usual transplant care in 70 HSCT survivors. Allogeneic HSCT survivors at 100 days post-HSCT are eligible for the study. The PATH intervention, tailored to the needs of HSCT survivors in the acute recovery phase, focuses on gratitude, strengths, and meaning. Our primary aims are to determine feasibility (e.g., session completion, rate of recruitment) and acceptability (e.g., weekly session ratings). Our secondary aim is to test the preliminary efficacy of the intervention on patient-reported outcomes (e.g., anxiety symptoms, QOL).

DISCUSSION

If the PATH intervention is feasible, a larger randomized, controlled efficacy trial will be indicated. Additionally, we anticipate that the results from this RCT will guide the development of other clinical trials and larger efficacy studies of positive psychology interventions in vulnerable oncological populations beyond HSCT.

Association Between Opioid Dose Reduction Rates and Overdose Among Patients Prescribed Long-Term Opioid Therapy

BACKGROUND

Tapering long-term opioid therapy is an increasingly common practice, yet rapid opioid dose reductions may increase the risk of overdose. The objective of this study was to compare overdose risk following opioid dose reduction rates of ≤10%, 11% to 20%, 21% to 30%, and >30% per month to stable dosing.

METHODS

We conducted a retrospective cohort study in three health systems in Colorado and Wisconsin. Participants were patients ≥18 years of age prescribed long-term opioid therapy between January 1, 2006, and June 30, 2019. Five opioid dosing patterns and drug overdoses (fatal and nonfatal) were identified using electronic health records, pharmacy records, and the National Death Index. Cox proportional hazard regression was conducted on a propensity score-weighted cohort to estimate adjusted hazard ratios (aHRs) for follow-up periods of 1, 3, 6, 9, and 12 months after a dose reduction.

RESULTS

In a cohort of 17 540 patients receiving long-term opioid therapy, 42.7% of patients experienced a dose reduction. Relative to stable dosing, a dose reduction rate of >30% was associated with an increased risk of overdose and the aHR estimates decreased as the follow-up increased; the aHRs for the 1-, 6- and 12-month follow-ups were 5.33 (95% CI, 1.98-14.34), 1.81 (95% CI,1.08-3.03), and 1.49 (95% CI, 0.97-2.27), respectively. The slower tapering rates were not associated with overdose risk.

CONCLUSIONS

Patients receiving long-term opioid therapy exposed to dose reduction rates of >30% per month had increased overdose risk relative to patients exposed to stable dosing. Results support the use of slow dose reductions to minimize the risk of overdose.

Differences in medication adherence by sex and organ type among adolescent and young adult solid organ transplant recipients

BACKGROUND

Identification of differences in medication adherence by sex or organ type may help in planning interventions to optimize outcomes. We compared immunosuppressive medication adherence between males and females, and between kidney, liver and heart transplant recipients.

METHODS

This multicenter study of prevalent kidney, liver and heart transplant recipients 14-25 years assessed adherence 3 times (0, 3, 6 months post-enrollment) with the BAASIS self-report tool. At each visit, participants were classified as adherent if they missed no doses in the prior 4 weeks and non-adherent otherwise. Adherence was also assessed using the coefficient of variation (CV) of tacrolimus trough levels; CV < 30% was classified as adherent. We used multivariable mixed effects logistic regression models adjusted for potential confounders to compare adherence by sex and by organ.

RESULTS

Across all visits, males (n = 150, median age 20.4 years, IQR 17.2-23.3) had lower odds of self-reported adherence than females (n = 120, median age 19.8 years, IQR 17.1-22.7) (OR 0.41, 95% CI 0.21-0.80) but higher odds of adherence by tacrolimus CV (OR 2.50, 95% CI 1.30-4.82). No significant differences in adherence (by self-report or tacrolimus CV) were noted between the 184 kidney, 58 liver, and 28 heart recipients.

CONCLUSION

Females show better self-reported adherence than males but greater variability in tacrolimus levels. Social desirability bias, more common in females than males, may contribute to better self-reported adherence among females. Higher tacrolimus variability among females may reflect biologic differences in tacrolimus metabolism between males and females rather than sex differences in adherence. There were no significant differences in adherence by organ type.

Population pharmacokinetics of sublingually administered tacrolimus in infants and young children with liver transplantation

AIMS

Pharmacokinetics of tacrolimus after sublingual administration is not characterized in paediatric liver transplant patients. Therefore, we aimed to develop a population pharmacokinetic model of sublingually administered tacrolimus in patients who cannot swallow the capsules due to their age, sedation status and/or mechanical ventilation during the first weeks post-transplantation.

METHODS

Demographic, clinical and pharmacological variables, including tacrolimus whole blood concentrations obtained from therapeutic drug monitoring and data from dense-sampling pharmacokinetic profiles, were recorded in 26 paediatric patients with biliary atresia who underwent liver transplantation between 2016 and 2021. Population pharmacokinetic analysis was performed with NONMEM v7.4.

RESULTS

Disposition of tacrolimus was best characterized by a 2-compartment model with clearance achieving half of the maximum elimination capacity (CL_MAX  = 4.1 L/h) at 4.6 days post-transplantation (T₅₀ ). Compared to sedated patients, nonsedated status showed an increased first-order absorption rate constant (1.1 vs. 0.1 h^-1 ) and a 24% reduction in bioavailability (F_NS ) at 14 days post-transplant. The model was able to explain the oral absorption pattern in nonsedated patients as the result of gut bioavailability (0.9) and hepatic extraction ratio, with the latter being responsible for first-pass effects. Estimates of interindividual variability remained moderate (25.9% for the gut bioavailability) to high (79.8% for the apparent volume of distribution of the central compartment, and 101% for T₅₀ ).

CONCLUSION

A population pharmacokinetic model of sublingually administered tacrolimus in paediatric patients was developed to characterize different absorption mechanisms. Once the model is externally validated, the effect of post-transplant time on clearance and the sedation status may be considered in routine dosing management.

Diabetes is a significant and independent predictor for tacrolimus immediate release and LCP-tacrolimus conversion ratios

Diabetes (DM) is a common comorbidity in transplant patients with known effects on gastrointestinal (GI) motility and absorption; however, DM's impact on immediate release (IR) tacrolimus to LCP-tacrolimus (LCP) conversion ratios has not been studied. This multivariable analysis of a retrospective longitudinal cohort study included kidney transplant recipients converted from IR to LCP between 2019 and 2020. The primary outcome was IR to LCP conversion ratio based on DM status. Other outcomes included tacrolimus variability, rejection, graft loss, and death. Of the 292 patients included, 172 patients had DM and 120 did not. The IR:LCP conversion ratio was significantly higher with DM (67.5% ± 21.1% no DM vs. 79.8% ± 28.7% in DM; P < .001). In multivariable modeling, DM was the only variable significantly and independently associated with IR:LCP conversion ratios. No difference was observed in rejection rates. Graft (97.5% no DM vs. 92.4% in DM; P = .062) and patient survival (100% no DM vs. 94.8% in DM; P = .011) were lower with DM. The presence of DM significantly increased the IR:LCP conversion ratio by 13%-14%, compared to patients without DM. On multivariable analysis, DM was the only significant predictor of conversion ratios, potentially related to GI motility or absorption differences.

Reliability and feasibility of home-based dried blood spot in therapeutic drug monitoring: a systematic review and meta-analysis

PURPOSE

Dried blood spot (DBS) is one of promising home sampling methods for therapeutic drug monitoring (TDM). However, the associated reliability and feasibility (including yield, adherence, and preference), which are criteria for the promotion of home-based DBS, remain unknown. This systematic review and meta-analysis aimed to evaluate the reliability and feasibility of TDM using DBS sampling.

METHODS

In this study, a combination of MeSH and free terms for (dried blood spot*[title/abstract])AND ("Drug Monitoring"[Mesh])AND(home OR venous)was surveyed using EMBASE, PubMed, Cochrane Library, and Web of Science upon gathering published. we registered this study protocol with the International Prospective Registry of Systematic Reviews (CRD42021247559).

RESULTS

Approximately half (35/75) of the evaluations reported good agreement between DBS and plasma, and the results for drugs with poor agreement may be improved using a haematocrit-based physiological equation. The yield and adherence to home-based DBS exceeded 87%, and questionnaire-based preference for DBS was 77%.

CONCLUSIONS

DBS may be a reliable and feasible home sampling method; however, it requires intricate design and evaluation before implementation.

Results From a Proficiency Testing Pilot for Immunosuppressant Microsampling Assays

BACKGROUND

Therapeutic drug monitoring (TDM) of immunosuppressive drugs is important for the prevention of allograft rejection in transplant patients. Several hospitals offer a microsampling service that provides patients the opportunity to sample a drop of blood from a fingerprick at home that can then be sent to the laboratory by mail. The aim of this study was to pilot an external quality control program.

METHODS

Fourteen laboratories from 7 countries participated (fully or partly) in 3 rounds of proficiency testing for the immunosuppressants tacrolimus, ciclosporin, everolimus, sirolimus, and mycophenolic acid. The microsampling devices included the following: Whatman 903 and DMPK-C, HemaXis, Mitra, and Capitainer-B. All assays were based on liquid chromatography with tandem mass spectrometry. In round 2, microsamples as well as liquid whole blood samples were sent, and 1 of these samples was a patient sample.

RESULTS

Imprecision CV% values for the tacrolimus microsamples reported by individual laboratories ranged from 13.2% to 18.2%, 11.7%-16.3%, and 12.2%-18.6% for rounds 1, 2, and 3, respectively. For liquid whole blood (round 2), the imprecision CV% values ranged from 3.9%-4.9%. For the other immunosuppressants, the results were similar. A great variety in analytical procedures was observed, especially the extraction method. For the patient sample, the microsample results led to different clinical decisions compared with that of the whole blood sample.

CONCLUSIONS

Immunosuppressant microsampling methods show great interlaboratory variation compared with whole blood methods. This variation can influence clinical decision-making. Thus, harmonization and standardization are needed. Proficiency testing should be performed regularly for laboratories that use immunosuppressant microsampling techniques in patient care.

Dried blood microsampling-assisted therapeutic drug monitoring of immunosuppressants: An overview

In the field of solid organ transplantation, chemotherapy and autoimmune disorders, treatment with immunosuppressant drugs requires intensive follow-up of the blood concentrations via therapeutic drug monitoring (TDM) because of their narrow therapeutic window and high intra- and inter-subject variability. This requires frequent hospital visits and venepunctures to allow the determination of these analytes, putting a high burden on the patients. In the context of patient-centric thinking, it is becoming increasingly established that at least part of these conventional blood draws could be replaced by microsampling, allowing home-sampling and increasing the quality of life for these patients. In this review we discuss the published methods - mostly using liquid chromatography coupled to tandem mass spectrometry - that have utilized (volumetric) dried blood samples as an alternative for conventional liquid whole blood for the TDM of immunosuppressant drugs. Furthermore, some pre-analytical considerations using DBS or volumetric alternatives are considered, as well as the applicability on clinical samples. The implementation status in clinical practice is also discussed, including (1) the cost-effectiveness of this approach compared to venepuncture, (2) the availability of multiplexed methods, (3) the status of harmonization and (4) patient perception. A brief perspective on potential future developments for the dried blood-based TDM of immunosuppressant drugs is provided, by considering how obstacles for the implementation of these strategies into clinical practice might be overcome.

Volumetric Absorptive Microsampling to Enhance the Therapeutic Drug Monitoring of Tacrolimus and Mycophenolic Acid: A Systematic Review and Critical Assessment

BACKGROUND

Volumetric absorptive microsampling (VAMS) is an emerging technique that may support multisample collection to enhance therapeutic drug monitoring in solid organ transplantation. This review aimed to assess whether tacrolimus and mycophenolic acid can be reliably assayed using VAMS and to identify knowledge gaps by providing granularity to existing analytical methods and clinical applications.

METHODS

A systematic literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, Embase, and Scopus databases were accessed for records from January 2014 to April 2022 to identify scientific reports on the clinical validation of VAMS for monitoring tacrolimus and mycophenolic acid concentrations. Data on the study population, sample sources, analytical methods, and comparison results were compiled.

RESULTS

Data from 12 studies were collected, including 9 studies pertaining to tacrolimus and 3 studies on the concurrent analysis of tacrolimus and mycophenolic acid. An additional 14 studies that provided information relevant to the secondary objectives (analytical validation and clinical application) were also included. The results of the clinical validation studies generally met the method agreement requirements described by regulatory agencies, but in many cases, it was essential to apply correction factors.

CONCLUSIONSS

Current evidence suggests that the existing analytical methods that use VAMS require additional optimization steps for the analysis of tacrolimus and mycophenolic acid. The recommendations put forth in this review can help guide future studies in achieving the goal of improving the care of transplant recipients by simplifying multisample collection for the dose optimization of these drugs.

Pharmacokinetic Model Based on Stochastic Simulation and Estimation for Therapeutic Drug Monitoring of Tacrolimus in Korean Adult Transplant Recipients

BACKGROUND

Tacrolimus shows high variability in inter- and intraindividual pharmacokinetics (PK); therefore, it is important to develop an appropriate model for accurate therapeutic drug monitoring (TDM) procedures. This study aimed to develop a pharmacokinetic model for tacrolimus that can be used for TDM procedures in Korean adult transplant recipients by integrating published models with acquired real-world TDM data and evaluating clinically meaningful covariates.

METHODS

Clinical data of 1829 trough blood samples from 269 subjects were merged with simulated data sets from published models and analyzed using a nonlinear mixed-effect model. The stochastic simulation and estimation (SSE) method was used to obtain the final parameter estimates.

RESULTS

The final estimated values for apparent clearance, the volume of distribution, and absorption rate were 21.2 L/h, 510 L, and 3.1/h, respectively. The number of postoperative days, age, body weight, and type of transplant organs were the major clinical factors affecting tacrolimus PK.

CONCLUSIONS

A tacrolimus PK model that can incorporate published PK models and newly collected data from the Korean population was developed using the SSE method. Despite the limitations in model development owing to the nature of TDM data, the SSE method was useful in retrieving complete information from the TDM data by integrating published PK models while maintaining the variability of the model.

Combined impact of the inter and intra-patient variability of tacrolimus blood level on allograft outcomes in kidney transplantation

INTRODUCTION

Tacrolimus (TAC) has been widely used as an immunosuppressant after kidney transplantation (KT); however, the combined effects of intra-patient variability (IPV) and inter-patient variability of TAC-trough level (C0) in blood remain controversial. This study aimed to determine the combined impact of TAC-IPV and TAC inter-patient variability on allograft outcomes of KT.

METHODS

In total, 1,080 immunologically low-risk patients who were not sensitized to donor human leukocyte antigen (HLA) were enrolled. TAC-IPV was calculated using the time-weighted coefficient variation (TWCV) of TAC-C0, and values > 30% were classified as high IPV. Concentration-to-dose ratio (CDR) was used for calculating TAC inter-patient variability, and CDR < 1.05 ng•mg/mL was classified as rapid metabolizers (RM). TWCV was calculated based on TAC-C0 up to 1 year after KT, and CDR was calculated based on TAC-C0 up to 3 months after KT. Patients were classified into four groups according to TWCV and CDR: low IPV/non-rapid metabolizer (NRM), high IPV/NRM, low IPV/RM, and high IPV/RM. Subgroup analysis was performed for pre-transplant panel reactive antibody (PRA)-positive and -negative patients (presence or absence of non-donor-specific HLA-antibodies). Allograft outcomes, including deathcensored graft loss (DCGL) and biopsy-proven allograft rejection (BPAR), were compared.

RESULTS

The incidences of DCGL, BPAR, and overall graft loss were the highest in the high-IPV/RM group. In addition, a high IPV/RM was identified as an independent risk factor for DCGL. The hazard ratio of high IPV/RM for DCGL and the incidence of active antibody-mediated rejection were considerably increased in the PRA-positive subgroup.

DISCUSSION

High IPV combined with RM (inter-patient variability) was closely related to adverse allograft outcomes, and hence, more attention must be given to pre-transplant PRA-positive patients.

Volumetric microsampling for simultaneous remote immunosuppressant and kidney function monitoring in outpatient kidney transplant recipients

AIMS

Immunosuppressant and kidney function monitoring are crucial for kidney transplant recipient follow-up. Microsamples enable remote sampling and minimise patient burden as compared to conventional venous sampling at the clinic. We developed a liquid chromatography-tandem mass spectrometry assay to quantify tacrolimus, mycophenolic acid (MPA), creatinine and iohexol in dried blood spot (DBS), and volumetric absorptive microsample (VAMS) samples.

METHODS

The assay was successfully validated analytically for all analytes. Clinical validation was conducted by direct comparison of paired DBS, VAMS and venous reference samples from 25 kidney transplant recipients. Patients received iohexol 5-15 minutes before immunosuppressant intake and were sampled 0, 1, 2 and 3 hours thereafter, enabling tacrolimus and MPA area under the concentration-time curve (AUC) and creatinine-based and iohexol-based glomerular filtration rate (GFR) estimation. Method agreement was evaluated using Passing-Bablok regression, Bland-Altman analysis and the percentages of values within 15-30% of the reference (P₁₅ -P₃₀ ) with a P₂₀ acceptance threshold of 80%.

RESULTS

For DBS samples, method agreement was excellent for tacrolimus trough concentrations (n = 25, P₁₅  = 92.0%) and AUCs (n = 25; P₂₀  = 95.8%) and adequate for creatinine-based GFR trend monitoring (n = 25; P₂₀  = 80%). DBS-based MPA AUC assessment showed suboptimal agreement (n = 16; P₂₀  = 68.8%), but was considered acceptable given its P₃₀ of 100%. The assay performed inadequately for DBS-based iohexol GFR determination (n = 24; P₂₀  = 75%). The VAMS technique generally showed inferior performance, but can be considered for certain situations.

CONCLUSION

The assay was successfully validated for tacrolimus, MPA and creatinine quantification in DBS samples, enabling simultaneous remote kidney function trend monitoring and immunosuppressant therapeutic drug monitoring in kidney transplant recipients.

Clinical association between tacrolimus intra-patient variability and liver transplantation outcomes in patients with and without hepatocellular carcinoma

Tacrolimus is the mainstay of immunosuppression in liver transplantation to prevent rejection. However, the clinical use of tacrolimus is complicated by its narrow therapeutic window and significant intra-patient variability (IPV). High tacrolimus IPV is associated with overexposure and adverse effects, including malignancy. The effects of tacrolimus IPV in liver transplant recipients with and without hepatocellular carcinoma (HCC) are unknown. We investigated the association between tacrolimus IPV and transplant outcomes in 636 liver transplant patients. Tacrolimus IPV was determined by calculating the coefficient of variance (CV) of outpatient tacrolimus trough levels from 3 to 12 months after transplantation. High tacrolimus IPV was defined as CV > 30%. Patients were grouped according to tacrolimus IPV and HCC status. Among 636 liver transplant patients, 349 had HCC and 287 had no HCC. Overall survival in HCC patients was significantly reduced with high tacrolimus IPV (P < 0.001), whereas survival of non-HCC patients was not associated with tacrolimus IPV. Multivariable analysis confirmed the independent association between high tacrolimus IPV and overall mortality in HCC patients (HR, 3.010; 95% CI, 1.084–4.918). HCC recurred in 59 patients (16.9%) post-transplantation. After adjusting for donor/recipient factors, immunosuppression, and tumor characteristics, high tacrolimus IPV was independently associated with an increased risk of HCC recurrence (HR, 2.196; 95% CI, 1.272–3.791). High tacrolimus IPV was associated with significantly increased risks of overall mortality and HCC recurrence in liver transplant recipients with HCC.

Next-Generation Personalized Medicine: Implementation of Variability Patterns for Overcoming Drug Resistance in Chronic Diseases

Chronic diseases are a significant healthcare problem. Partial or complete non-responsiveness to chronic therapies is a significant obstacle to maintaining the long-term effect of drugs in these patients. A high degree of intra- and inter-patient variability defines pharmacodynamics, drug metabolism, and medication response. This variability is associated with partial or complete loss of drug effectiveness. Regular drug dosing schedules do not comply with physiological variability and contribute to resistance to chronic therapies. In this review, we describe a three-phase platform for overcoming drug resistance: introducing irregularity for improving drug response; establishing a deep learning, closed-loop algorithm for generating a personalized pattern of irregularity for overcoming drug resistance; and upscaling the algorithm by implementing quantified personal variability patterns along with other individualized genetic and proteomic-based ways. The closed-loop, dynamic, subject-tailored variability-based machinery can improve the efficacy of existing therapies in patients with chronic diseases.

Patterns in Tacrolimus Variability and Association with De Novo Donor-Specific Antibody Formation in Pediatric Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

High tacrolimus intrapatient variability has been associated with inferior graft outcomes in patients with kidney transplants. We studied baseline patterns of tacrolimus intrapatient variability in pediatric patients with kidney transplants and examined these patterns in relation to C1q-binding de novo donor-specific antibodies.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All tacrolimus levels in participants who underwent kidney-only transplantation at a single pediatric center from 2004 to 2018 (with at least 12-month follow-up, followed until 2019) were analyzed to determine baseline variability. Intrapatient variability was defined using the coefficient of variation (SD/mean ×100%) of all samples in a 6-month moving window. Routine de novo donor-specific antibody measurements were available for a subgroup of patients transplanted in 2010-2018. Cox proportional hazards models using tacrolimus intrapatient variability as a time-varying variable were used to examine the association between intrapatient variability and graft outcomes. The primary outcome of interest was C1q-binding de novo donor-specific antibody formation.

RESULTS

Tacrolimus intrapatient variability developed a steady-state baseline of 30% at 10 months post-transplant in 426 patients with a combined 31,125 tacrolimus levels. Included in the outcomes study were 220 patients, of whom 51 developed C1q-binding de novo donor-specific antibodies. De novo donor-specific antibody formers had higher intrapatient variability, with a median of 38% (interquartile range, 28%-48%) compared with 28% (interquartile range, 20%-38%) for nondonor-specific antibody formers (P<0.001). Patients with high tacrolimus intrapatient variability (coefficient of variation >30%) had higher risk of de novo donor-specific antibody formation (hazard ratio, 5.35; 95% confidence interval, 2.45 to 11.68). Patients in the top quartile of tacrolimus intrapatient variability (coefficient of variation >41%) had the strongest association with C1q-binding de novo donor-specific antibody formation (hazard ratio, 11.81; 95% confidence interval, 4.76 to 29.27).

CONCLUSIONS

High tacrolimus intrapatient variability was strongly associated with de novo donor-specific antibody formation.

High intrapatient variability of tacrolimus exposure associated with poorer outcomes in liver transplantation

Tacrolimus (TAC) is a dose‐dependent immunosuppressor with considerable intrapatient variability (IPV) in its pharmacokinetics. The aim of this work is to ascertain the association between TAC IPV at 6 months after liver transplantation (LT) and patient outcome. This single‐center cohort study retrospectively analyzed adult patients who underwent transplantation from 2015 to 2019 who survived the first 6 months with a functioning graft. The primary end point was the patient’s probability of death and the secondary outcome was the loss of renal function between month 6 and the last follow‐up. TAC IPV was estimated by calculating the coefficient of variation (CV) of the dose‐corrected concentration (C₀/D) between the third and sixth months post‐LT. Of the 140 patients who underwent LT included in the study, the low‐variability group (C₀/D CV < 27%) comprised 105 patients and the high‐variability group (C₀/D CV ≥ 27%) 35 patients. One‐, 3‐, and 5‐year patient survival rates were 100%, 82%, and 72% in the high‐variability group versus 100%, 97%, and 93% in the low‐variability group, respectively (p = 0.005). Moreover, significant impaired renal function was observed in the high‐variability group at 1 year (69 ± 16 ml/min/1.73 m² vs. 78 ± 16 ml/min/1.73 m², p = 0.004) and at 2 years post‐LT (69 ± 17 ml/min/1.73 m² vs. 77 ± 15 ml/min/1.73 m², p = 0.03). High C₀/D CV 3–6 months remained independently associated with worse survival (hazard ratio = 3.57, 95% CI = 1.32–9.67, p = 0.012) and loss of renal function (odds ratio = 3.47, 95% CI = 1.30–9.20, p = 0.01). Therefore, high IPV between the third and sixth months appears to be an early and independent predictor of patients with poorer liver transplant outcomes.

Evaluation of the Relationship between Medication Adherence and Tacrolimus Coefficient of Variation

Introduction: High tacrolimus intrapatient variability is associated with poor outcomes following transplantation. A commonly hypothesized cause of this variability is medication non-adherence, but this has not been conclusively demonstrated. Research Question: The purpose of this study was to evaluate the relationship between medication adherence and tacrolimus intrapatient variability. Design: This was a retrospective cohort study of kidney transplant recipients. Adherence was assessed at the 12-month clinic visit as a composite of patient self-report, pharmacist assessment, and lab monitoring frequency. Tacrolimus intrapatient variability was calculated as the coefficient of variation (CV). Linear regression and receiver operating curve (ROC) analysis were used to assess the relationship between adherence and CV. Results: Nonadherence was identified in 37.5% of patients. The median CV was 27.1% for adherent patients and 29.8% for non-adherent patients (P = 0.051). In the multivariable analysis, the only significant predictor of CV was the incidence of dose changes (P = 0.002). ROC analysis demonstrated poor discriminant power with an AUC of 0.597. Discussion: The results fail to support a clinically meaningful relationship between medication adherence and tacrolimus CV. There is very little evidence at this time that adherence is the primary contributing factor to tacrolimus intrapatient variability and, by extension, that CV can be used as a surrogate for adherence.

The Role of Intra-Patient Variability of Tacrolimus Drug Concentrations in Solid Organ Transplantation: A Focus on Liver, Heart, Lung and Pancreas

Tacrolimus, the keystone immunosuppressive drug administered after solid organ transplantation, presents a narrow therapeutic index and wide inter- and intra-patient pharmacokinetic variability (IPV). The latter has been fairly studied in kidney transplantation, where it could impact outcomes. However, literature about other transplanted organ recipients remains inconclusive. This review aimed at summarizing the evidence about the IPV of tacrolimus concentrations outside of the scope of kidney transplantation. First, factors influencing IPV will be presented. Then, the potential of IPV as a biomarker predictive of graft outcomes will be discussed in liver, heart, lung and pancreas transplantation. Lastly, strategies to reduce IPV will be reviewed, with the ultimate objective being ready-to-implement solutions in clinical practice by transplantation professionals.

A Subject-Tailored Variability-Based Platform for Overcoming the Plateau Effect in Sports Training: A Narrative Review

The plateau effect in training is a significant obstacle for professional athletes and average subjects. It evolves from both the muscle-nerve-axis-associated performance and various cardiorespiratory parameters. Compensatory adaptation mechanisms contribute to a lack of continuous improvement with most exercise regimens. Attempts to overcome this plateau in exercise have been only partially successful, and it remains a significant unmet need in both healthy subjects and those suffering from chronic neuromuscular, cardiopulmonary, and metabolic diseases. Variability patterns characterize many biological processes, from cellular to organ levels. The present review discusses the significant obstacles in overcoming the plateau in training and establishes a platform to implement subject-tailored variability patterns to prevent and overcome this plateau in muscle and cardiorespiratory performance.

Comparison of conventional dried blood spots and volumetric absorptive microsampling for tacrolimus and mycophenolic acid determination

Therapeutic drug monitoring (TDM) of immunosuppressants is essential to avoid either rejection or toxicity after solid organ transplantations. Capillary microsampling approaches are an outstanding alternative to conventional venous sampling for TDM (easy and non-invasive collection, enabling self-sampling, and cost-saving shipment, processing and storage). Volumetric absorptive microsampling (VAMS) has gained importance in the last years, as it was meant to overcome the hematocrit (Hct) related issues commonly associated to DBS analysis. Despite all the benefits, microsampling techniques performance (including a thorough clinical validation) should be set up before their implementation in clinical practice. The aim of this study was to perform a clinical validation for both tacrolimus (TAC) and mycophenolic acid (MPA) in both DBS and Mitra™ VAMS. For the clinical validations, two different requirements were set up: analytical (following EMA and FDA guidelines) and clinical (following the Royal College of Pathologists of Australasia -RCPA- recommendations) acceptance criteria. For DBS, both analytical and clinical acceptance criteria were fulfilled for TAC, with 98.7% and 95% of the paired samples within the preset limits, respectively. For MPA, the analytical criterion was met (70.6% of paired specimens), although only half of the pairs were within the clinical limits. For VAMS, the clinical validation for both TAC and MPA showed good correlations but significant lower concentrations in VAMS compared to the routine matrices. After VAMS concentrations correction, the analytical requirement was fulfilled for both analytes (71.1% for TAC, 75% for MPA), although the more restrictive criteria recommended by the RCPA were not met for any analyte (half of the samples fell within the acceptance area). In addition, no significant Hct impact on the quantification was found in any case. Also, a preliminary home-sampling trial was set up, showing promising results. Moreover, a comparison between VAMS vs. DBS analytical and clinical performances was carried out, including a home-sampling trial, sample quality results and costs. Although the analytical performance for both VAMS and DBS was similar, DBS were superior regarding clinical criteria, sampling quality and cost.

Detecting, preventing, and treating non-adherence to immunosuppression after kidney transplantation

Medication non-adherence (MNA) is a major issue in kidney transplantation and it is associated with increased risk of rejection, allograft loss, patients’ death and higher healthcare costs. Despite its crucial importance, it is still unclear what are the best strategies to diagnose, prevent and treat MNA. MNA can be intentional (deliberate refusal to take the medication as prescribed) or unintentional (non-deliberate missing the prescribed medication). Its diagnosis may rely on direct methods, aiming at measuring drug ingestions, or indirect methods that analyse the habits of patients to adhere to correct drug dose (taking adherence) and interval (time adherence). Identifying individual risk factors for MNA may provide the basis for a personalized approach to the treatment of MNA. Randomized control trials performed so far have tested a combination of strategies, such as enhancing medication adherence through the commitment of healthcare personnel involved in drug distribution, the use of electronic reminders, therapy simplification or various multidisciplinary approaches to maximize the correction of individual risk factors. Although most of these approaches reduced MNA in the short-term, the long-term effects on MNA and, more importantly, on clinical outcomes remain unclear. In this review, we provide a critical appraisal of traditional and newer methods for detecting, preventing and treating non-adherence to immunosuppression after kidney transplantation from the perspective of the practising physician.

Nomograms for Predicting the Incidence of Late-Onset Acute Cellular Rejection in Patients After Pediatric Liver Transplantation

BACKGROUND

Late-onset acute cellular rejection (LACR) is a special type of acute rejection (AR) only rarely studied after pediatric liver transplantation (pLT). Our study aimed to explore the influencing factors of LACR after pLT and establish a nomogram to provide an individualized prediction of LACR after pLT.

MATERIALS AND METHODS

Data from 640 children who underwent pLT at Tianjin First Central Hospital from January 2016 to December 2019 were collected as part of this retrospective study. The nomogram was then established through the results of the multivariable analysis.

RESULTS

Forty-one patients experienced LACR > 1 ≤ 2 years after pLT. Cold ischemia time, donor-specific antibodies (DSAs), and tacrolimus concentration were independent influencing factors, and a nomogram was established with an AUC value of 0.834 (95% confidence interval, 0.755-0.912). Ten-fold cross-validation showed that the accuracy of the nomogram was about 76%. Sixty-three patients experienced LACR > 2 years after pLT. Child-Pugh grade, cold ischemic time, DSAs, early acute cellular rejection, and tacrolimus concentration were independent influencing factors, and a nomogram was established with an AUC value of 0.827 (95% confidence interval, 0.774-0.881). Ten-fold cross-validation showed that the accuracy of the nomogram was about 80.9%.

CONCLUSION

We established nomograms to predict the incidence of LACR > 1 ≤ 2 and > 2 years after pLT, respectively. The verification results showed that nomograms had good accuracy and clinical practicability.

A randomized crossover study comparing different tacrolimus formulations to reduce intrapatient variability in tacrolimus exposure in kidney transplant recipients

A high intrapatient variability (IPV) in tacrolimus exposure is a risk factor for poor long‐term outcomes after kidney transplantation. The main objective of this trial was to investigate whether tacrolimus IPV decreases after switching patients from immediate‐release (IR)‐tacrolimus to either extended‐release (ER)‐tacrolimus or LifeCyclePharma (LCP)‐tacrolimus. In this randomized, prospective, open‐label, cross‐over trial, adult kidney transplant recipients on a stable immunosuppressive regimen, including IR‐tacrolimus, were randomized for conversion to ER‐tacrolimus or LCP‐tacrolimus, and for the order in which IR‐tacrolimus and the once‐daily formulations were taken. Patients were followed 6 months for each formulation, with monthly tacrolimus predose concentration assessments to calculate the IPV. The IPV was defined as the coefficient of variation (%) of dose corrected predose concentrations. Ninety‐two patients were included for analysis of the primary outcome. No significant differences between the IPV of IR‐tacrolimus (16.6%) and the combined once‐daily formulations (18.3%) were observed (% difference +1.7%, 95% confidence interval [CI] −1.1% to ‒4.5%, p = 0.24). The IPV of LCP‐tacrolimus (20.1%) was not significantly different from the IPV of ER‐tacrolimus (16.5%, % difference +3.6%, 95% CI −0.1% to 7.3%, p = 0.06). In conclusion, the IPV did not decrease after switching from IR‐tacrolimus to either ER‐tacrolimus or LCP‐tacrolimus. These results provide no arguments to switch kidney transplant recipients from twice‐daily (IR) tacrolimus formulations to once‐daily (modified‐release) tacrolimus formulations when the aim is to lower the IPV.

A digital health platform for assisting the diagnosis and monitoring of COVID-19 progression: An adjuvant approach for augmenting the antiviral response and mitigating the immune-mediated target organ damage

Coronavirus disease 2019 (COVID-19), which is a respiratory illness associated with high mortality, has been classified as a pandemic. The major obstacles for the clinicians to contain the disease are limited information availability, difficulty in disease diagnosis, predicting disease prognosis, and lack of disease monitoring tools. Additionally, the lack of valid therapies has further contributed to the difficulties in containing the pandemic. Recent studies have reported that the dysregulation of the immune system leads to an ineffective antiviral response and promotes pathological immune response, which manifests as ARDS, myocarditis, and hepatitis. In this study, a novel platform has been described for disseminating information to physicians for the diagnosis and monitoring of patients with COVID-19. An adjuvant approach using compounds that can potentiate antiviral immune response and mitigate COVID-19-induced immune-mediated target organ damage has been presented. A prolonged beneficial effect is achieved by implementing algorithm-based individualized variability measures in the treatment regimen.

High Intrapatient Variability in Tacrolimus Exposure Calculated Over a Long Period Is Associated With De Novo Donor-Specific Antibody Development and/or Late Rejection in Thai Kidney Transplant Patients Receiving Concomitant CYP3A4/5 Inhibitors

BACKGROUND

High intrapatient variability in tacrolimus trough levels (Tac IPV) is associated with poor allograft outcomes. Tac IPV was previously calculated using trough levels 6-12 months after kidney transplantation (KT). Data on the accuracy of Tac IPV calculation over a longer period, the association between high Tac IPV and donor-specific antibody (DSA) development after KT in Asian patients, and the role of IPV in patients receiving concomitant cytochrome P450 (CYP)3A4/5 inhibitors (CYPinh) are limited.

METHODS

A retrospective review of patients who underwent KT at our center in 2005-2015, and who received Tac with mycophenolate during the first 2 years after KT was performed. IPV was calculated using Tac levels adjusted by dosage. DSA was monitored annually after KT using a Luminex microbead assay.

RESULTS

In total, 236 patients were enrolled. CYPinh were prescribed to 189 patients (80.1%): 145 (61.4%), 31 (13.1%), and 13 (5.5%) received diltiazem, fluconazole, and ketoconazole, respectively. Mean IPV calculated from adjusted Tac levels for 6-12 months (IPV6-12) and 6-24 months (IPV6-24) after KT were 20.64% ± 11.68% and 23.53% ± 10.39%, respectively. Twenty-six patients (11%) showed late rejection and/or DSA occurrence, and had significantly higher IPV6-24 (29.42% ± 13.78%) than others (22.77% ± 9.64%; P = 0.02). There was no difference in IPV6-12 (24.31% ± 14.98% versus 20.17% ± 10.90%; P = 0.18). IPV6-12 and IPV6-24 were comparable in patients who did and did not receive CYPinh. When using mean IPV6-24 as a cutoff, patients with higher IPV6-24 had a higher probability of developing DSA and/or late rejection (P = 0.048).

CONCLUSIONS

Tac IPV6-24 was higher and more significantly associated with DSA development and/or late rejection than Tac IPV6-12, independent of Tac trough level. This is the first study to demonstrate the impact of high IPV on DSA development in Asian patients, and that Tac IPV is comparable between patients with and without CYPinh.

Impact of once-daily ER-Tac on trough concentration variability in a stable AYA renal transplant recipient cohort

BACKGROUND

Successful renal transplantation requires complex medication regimens that rely on strict adherence to be effective. Variability in immunosuppression exposure, specifically tacrolimus, is associated with poor allograft outcomes. Wide intra-patient variability of tacrolimus trough concentrations (Vtac) is likely, in part, attributable to regimen complexity and poor medication adherence. Once-daily tacrolimus formulations create opportunity to simplify therapeutic regimens, and this study aims to evaluate their impact on Vtac and ultimately transplant outcomes.

METHODS

This retrospective cohort study investigated stable (AYA) renal transplant recipients converted from (IR-Tac) to (ER-Tac). Subjects served as their own controls. Vtac was assessed by measuring the (SD) of serial tacrolimus trough concentrations prior to and at four time points post-conversion to ER-Tac over 24-month follow-up. Secondary outcome measures included graft function, infection rates, and effect on modifiable treatment-related factors.

RESULTS

Twenty-eight AYA subjects were converted from IR-Tac to ER-Tac. Vtac significantly improved following conversion and was sustained for 24 months (Vtac₀ 2.32 vs. Vtac₂₄ 1.11, p .017). Renal function remained stable, and (BPAR) rates were modest (14%). Mean pill burden was reduced by 15%, and 42.9% of subjects achieved a once-daily medication regimen.

CONCLUSIONS

Conversion from IR-Tac to ER-Tac in this AYA population significantly improved Vtac with sustained effect over 2 years. This effect is likely attributable in part to simplification of the medication regimen and presumably improved medication adherence. Such conversion does not appear to compromise graft function for at least 2 years post-conversion.

No Apparent Influence of Nonadherence on Tacrolimus Intrapatient Variability in Stable Kidney Transplant Recipients

BACKGROUND

High intrapatient variability (IPV) in tacrolimus exposure has been associated with an increased risk of graft rejection and graft loss. It has been suggested that medication nonadherence has high impact on IPV. The objective of this study is to assess the relationship between tacrolimus IPV and medication nonadherence in stable kidney transplant recipients.

METHODS

This study was conducted within the Reducing Renal Function Deterioration trial (Netherlands Trial Register: NTR7256), which included stable kidney transplant recipients. Nonadherence was assessed quantitatively by electronic monitoring (EM) and qualitatively using the composite adherence score (CAS) consisting of patient self-reporting (Immunosuppressant Therapy Adherence Scale), a physician report, and the tacrolimus trough concentrations (C0). IPV in tacrolimus C0 and area under the concentration-time curves (AUCs) was evaluated at 5 and 3 sampling instances, respectively.

RESULTS

Data of 64 kidney transplant recipients (43 males, 21 females; mean age 53.6 years), mean time post-transplantation 5.4 years, were collected. Mean missed tacrolimus intake was 7% (0.3%-13.4%) based on EM, missing one intake every 2 weeks. Based on the CAS, 68.9% of the patients were categorized as nonadherent. The mean IPV was 17.9% (4.4%-65.3%) and 20.2% (2.5%-51.6%) for tacrolimus C0 and AUCs, respectively. The nonadherence data displayed a nonparametric distribution, with nonadherence scores mostly in the lower ranges. There was no significant difference in the mean IPV between adherent and nonadherent patients. There were no differences in EM, CAS, physician report, or time-in-therapeutic range, but patients with a low AUC IPV showed a slightly higher Immunosuppressant Therapy Adherence Scale score than those with a high AUC IPV (P = 0.035).

CONCLUSIONS

There was no apparent relationship between IPV and nonadherence in this motivated kidney transplant recipient population, with one missed tacrolimus dose every 2 weeks.

Improving Diuretic Response in Heart Failure by Implementing a Patient-Tailored Variability and Chronotherapy-Guided Algorithm

Heart failure is a major public health problem, which is associated with significant mortality, morbidity, and healthcare expenditures. A substantial amount of the morbidity is attributed to volume overload, for which loop diuretics are a mandatory treatment. However, the variability in response to diuretics and development of diuretic resistance adversely affect the clinical outcomes. Morevoer, there exists a marked intra- and inter-patient variability in response to diuretics that affects the clinical course and related adverse outcomes. In the present article, we review the mechanisms underlying the development of diuretic resistance. The role of the autonomic nervous system and chronobiology in the pathogenesis of congestive heart failure and response to therapy are also discussed. Establishing a novel model for overcoming diuretic resistance is presented based on a patient-tailored variability and chronotherapy-guided machine learning algorithm that comprises clinical, laboratory, and sensor-derived inputs, including inputs from pulmonary artery measurements. Inter- and intra-patient signatures of variabilities, alterations of biological clock, and autonomic nervous system responses are embedded into the algorithm; thus, it may enable a tailored dose regimen in a continuous manner that accommodates the highly dynamic complex system.

Evaluating the conversion to extended-release tacrolimus from immediate-release tacrolimus in liver transplant recipients

BACKGROUND

A new formulation of once daily extended-release tacrolimus (LCP-tac, Envarsus XR) was approved for use in the USA for kidney transplant recipients in 2015. There are limited data regarding real-world observations with conversion to LCP-tac in liver transplant recipients.

METHODS

We performed a retrospective analysis of liver transplant recipients treated with LCP-tac. Data collection included (1) reasons for switching to LCP-tac; (2) conversion ratio used; (3) kidney function at time of conversion and 3 months after; (4) outcomes of conversion [acute cellular rejection rates and cytomegalovirus (CMV) viremia] within 3 months of conversion.

RESULTS

Average conversion ratio used to achieve therapeutic drug level without further dose adjustment was 1:0.73 (SD 0.11). Median time after transplant was 508 days (IQR 736). Common reasons patients were switched to LCP-tac were from fluctuations in tacrolimus levels (44%) and adverse effect of tremor (32%). Among patients who were switched due to tremors 88% noted significant improvement. There was no difference in serum creatinine (P = 0.55) or glomerular filtration rate (P = 0.64) from baseline to 3 months postconversion. There were no episodes of acute cellular rejections or CMV viremia postconversion.

CONCLUSION

This observational study demonstrated that conversion of immediate-release tacrolimus to LCP-tac in liver transplant recipients was well tolerated and effective.

Point-of-Care Therapeutic Drug Monitoring for Precision Dosing of Immunosuppressive Drugs

BACKGROUND

Immunosuppressive drugs (ISD) are an essential tool in the treatment of transplant rejection and immune-mediated diseases. Therapeutic drug monitoring (TDM) for determination of ISD concentrations in biological samples is an important instrument for dose personalization for improving efficacy while reducing side effects. While currently ISD concentration measurements are performed at specialized, centralized facilities, making the process complex and laborious for the patient, various innovative technical solutions have recently been proposed for bringing TDM to the point-of-care (POC).

CONTENT

In this review, we evaluate current ISD-TDM and its value, limitations, and proposed implementations. Then, we discuss the potential of POC-TDM in the era of personalized medicine, and provide an updated review on the unmet needs and available technological solutions for the development of POC-TDM devices for ISD monitoring. Finally, we provide concrete suggestions for the generation of a meaningful and more patient-centric process for ISD monitoring.

SUMMARY

POC-based ISD monitoring may improve clinical care by reducing turnaround time, by enabling more frequent measurements in order to obtain meaningful pharmacokinetic data (i.e., area under the curve) faster reaction in case of problems and by increasing patient convenience and compliance. The analysis of the ISD-TDM field prompts the evolution of POC testing toward the development of fully integrated platforms able to support clinical decision-making. We identify 4 major areas requiring careful combined implementation: patient usability, data meaningfulness, clinicians' acceptance, and cost-effectiveness.

Therapeutic drug monitoring of immunosuppressive drugs in hepatology and gastroenterology

Immunosuppressive drugs have been key to the success of liver transplantation and are essential components of the treatment of inflammatory bowel disease (IBD) and autoimmune hepatitis (AIH). For many but not all immunosuppressants, therapeutic drug monitoring (TDM) is recommended to guide therapy. In this article, the rationale and evidence for TDM of tacrolimus, mycophenolic acid, the mammalian target of rapamycin inhibitors, and azathioprine in liver transplantation, IBD, and AIH is reviewed. New developments, including algorithm-based/computer-assisted immunosuppressant dosing, measurement of immunosuppressants in alternative matrices for whole blood, and pharmacodynamic monitoring of these agents is discussed. It is expected that these novel techniques will be incorporate into the standard TDM in the next few years.

Retrospective Analysis of Tacrolimus Intrapatient Variability as a Measure of Medication Adherence

Background:

Increased intrapatient variability (IPV) in tacrolimus levels is associated with graft rejection, de novo donor-specific antibodies, and graft loss. Medication nonadherence may be a significant contributor to high IPV.

Objective:

The objective of this study is to determine the utility of tacrolimus IPV in detecting nonadherence by examining the relationship between self-reported adherence and tacrolimus coefficient of variability (COV), a measure of IPV.

Design:

Retrospective cohort study.

Setting:

St. Michael’s Hospital, Toronto, Ontario.

Patients:

All patients who were at least 1-year post-kidney transplant as of March 31, 2019, prescribed tacrolimus as an immunosuppressant and had a self-reported adherence status. Patients were excluded from the primary analysis of examining the correlation between COV and self-reported adherence if they lacked a calculatable COV.

Measurements:

Self-reported adherence, COV, demographic data, transplant, and medication history.

Methods:

A modified Basel Assessment of Adherence to Immunosuppressive Medications Scale (BAASIS) administered by healthcare professionals to assess self-reported adherence was used. The COV of tacrolimus trough levels was calculated and its correlation to BAASIS response was noted. The median COV was used as a cutoff to examine the characteristics of patients deemed “high COV” and “low COV.”

Results:

A total of 591 patients fit the initial criteria; however, only 525 had a recent calculatable COV. Overall, 92.38% of the population were adherent by self-report. Primary analysis identified a COV of 25.2% and 29.6% in self-reported adherent and nonadherent patients, respectively, though the result was not significant (P = .2). Secondary analyses showed a significant correlation between younger age at transplant and at the time of adherence self-reporting with nonadherence (P = .01). In addition, there was a strong correlation between those nonadherent with routine post-transplant blood work and younger age (P < .01).

Limitations:

The limitations included modified nonvalidated BAASIS questionnaire, social desirability bias, BAASIS only administered in English, and patients with graft failure not active in clinic not being captured.

Conclusions:

The COV should not be used as the sole method for determining medication adherence. However, COV may have some utility in capturing individuals who are not adherent to their blood work or patients who are having a poor response to tacrolimus and should be switched to another medication.

Clinical significance of tacrolimus intra-patient variability on kidney transplant outcomes according to pre-transplant immunological risk

High intra-patient variability (IPV) of tacrolimus trough concentrations is increasingly recognized as a predictor of poor long-term outcomes in kidney transplant. However, there is a lack of information regarding the association between tacrolimus IPV and graft outcomes according to immunological risk. We analyzed tacrolimus IPV using the coefficient of variability from months 6-12 after transplantation in 1080 kidney transplant recipients. Patients were divided into two immunological risk groups based on pre-transplant panel reactive antibodies and donor-specific antibodies. High immunological risk was defined as panel reactive antibodies ≥ 20% or the presence of donor-specific antibodies. The effects of tacrolimus IPV on graft outcomes were significantly different between low and high immunological risk patients. A multivariable Cox regression model confirmed that high tacrolimus IPV was an independent risk factor for graft failure in the high risk group (HR, 2.90; 95% CI, 1.42-5.95, P = 0.004). In the high risk group, high tacrolimus IPV was also significantly associated with increased risk of antibody-mediated rejection (P = 0.006). In contrast, death-censored graft survival and antibody-mediated rejection in the low immunological risk group was not significantly different by tacrolimus IPV. High tacrolimus IPV significantly increases the risk of graft failure and antibody-mediated rejection in patients with high immunological risk.

Etiologies and Outcomes Associated With Tacrolimus Levels Out of a Typical Range That Lead to High Variability in Kidney Transplant Recipients

BACKGROUND

High tacrolimus intrapatient variability (tac IPV) is associated with poor outcomes in kidney transplantation, including rejection, donor-specific antibodies, and graft loss. A common cause of high tac IPV is related to patient nonadherence, but this is yet to be conclusively demonstrated.

METHODS

This was a longitudinal cohort study comprising adult kidney recipients, who received transplants between 2015 and 2017, with follow-ups through February 2020. The goal of this study was to identify the most common etiologies of tac levels outside the typical range, which lead to high tac IPV, and assess the etiology-specific associations between high tac IPV and graft outcomes. Multivariate Cox regression was used to assess time-to-event analyses.

RESULTS

In total, 537 adult kidney recipients were included; 145 (27%) were identified as having a high tac IPV (>40%) 3-102 months post-transplant. Common etiologies of tac levels significantly outside the standard goal range (6-12 ng/mL) leading to high tac IPV included patient nonadherence (20%), infections (19%), tac-related toxicities (17%), and undocumented issues (27%). In multivariable Cox modeling, those with high tac IPV because of nonadherence had a 3.5 times higher risk of late acute rejection (P = 0.019) and 2.2 times higher risk of late graft loss (P = 0.044). No other etiologies in the typical tac level range were significantly associated with either acute rejection or graft loss.

CONCLUSIONS

Although high tac IPV has many causes, only high tac IPV caused by nonadherence is consistently associated with poor allograft outcomes.

Clinical Implications of Tacrolimus Time in Therapeutic Range and Intrapatient Variability in Urban Renal Transplant Recipients Undergoing Early Corticosteroid Withdrawal

Tacrolimus demonstrates wide intrapatient and interpatient variability requiring therapeutic drug monitoring. The utility of tacrolimus time in therapeutic range (TTR) after renal transplantation (RT) under an early corticosteroid withdrawal (ECSWD) protocol is unknown. The purpose of this study is to assess the impact of tacrolimus TTR in an ECSWD RT population.

Materials

A retrospective analysis of adult RT recipients maintained on tacrolimus was conducted. Patients were excluded if they were on nonstandard protocol immunosuppression agents <12 months post-RT. Tacrolimus TTR was calculated using the Rosendaal method. Patients were divided into high (TTR-H) and low (TTR-L) TTR groups based on cohort median. The primary outcome was to compare the incidence of acute rejection 12 months post-RT. Secondary outcomes included comparing rejection subtypes, incidence of donor-specific antibody (DSA) and de novo DSA (dnDSA), risk factors for acute rejection and dnDSA development, and allograft function (serum creatinine and estimated glomerular filtration rate).

Results

A total of 193 patients were analyzed (TTR-H = 98 and TTR-L = 95). There was no difference in the incidence of acute rejection (TTR-H 20.4% versus TTR-L 20.0%; P = 0.944). Positive DSA posttransplant (odds ratio [OR], 3.62; 95% confidence interval [CI], 1.41-9.26; P = 0.007) was associated with a higher acute rejection at 12 months posttransplant. Mycophenolate dose reduction (OR, 2.82; 95% CI, 1.13-6.97; P = 0.025) and acute rejection (OR, 2.99; 95% CI, 1.09-8.18; P = 0.032) were associated with dnDSA formation. No difference in serum creatinine or estimated glomerular filtration rate was observed (P > 0.05).

Conclusions

Tacrolimus TTR was not significantly different with regards to acute rejection in an ECSWD population. Future studies are still needed to determine tacrolimus TTR thresholds post-RT and identify populations that may benefit from this intrapatient variability monitoring parameter.

Impact of Clotrimazole Fungal Prophylaxis on Tacrolimus Exposure in Kidney Transplant Recipients: A Retrospective Study

Tacrolimus, an immunosuppressant prescribed to reduce the risk of organ rejection, is metabolized by cytochrome P450 and is a substrate for P-glycoprotein. Many medications affect tacrolimus concentrations, making it difficult to maintain exposure within its narrow therapeutic index. Clotrimazole troches, prescribed to posttransplant recipients immediately for the first 30 days for oral candidiasis prevention, are considered nonsystemic. However, data suggest a potential drug interaction, affecting tacrolimus exposure. To assess the magnitude of the effect of clotrimazole on tacrolimus trough levels, 97 kidney transplant recipients, on a stable dose of tacrolimus, were retrospectively evaluated. Tacrolimus trough concentrations were analyzed 7 and 14 days before and after discontinuation of clotrimazole. The median change in tacrolimus trough level was -1.3 ng/mL (confidence interval, -2.5, -1.0; P < .001) at day 7 and -2.8 ng/mL (confidence interval, -3.3, -1.6; P < .001) at day 14 after clotrimazole discontinuation, from a median baseline of 8.9 ng/mL. Overall, a reduction in tacrolimus level was observed in 60% of patients after discontinuation of clotrimazole. When assessing the effect of race and sex, no influence was found on the degree of change in tacrolimus level after clotrimazole discontinuation. In conclusion, clotrimazole exerts a significant interaction on tacrolimus where close monitoring of tacrolimus trough levels after discontinuation of clotrimazole is warranted.