Severe elevations of FK506 blood concentration due to diarrhea in renal transplant recipients

Pharmacomicrobiomics: Immunosuppressive Drugs and Microbiome Interactions in Transplantation

The human microbiome is associated with human health and disease. Exogenous compounds, including pharmaceutical products, are also known to be affected by the microbiome, and this discovery has led to the field of pharmacomicobiomics. The microbiome can also alter drug pharmacokinetics and pharmacodynamics, possibly resulting in side effects, toxicities, and unanticipated disease response. Microbiome-mediated effects are referred to as drug-microbiome interactions (DMI). Rapid advances in the field of pharmacomicrobiomics have been driven by the availability of efficient bacterial genome sequencing methods and new computational and bioinformatics tools. The success of fecal microbiota transplantation for recurrent Clostridioides difficile has fueled enthusiasm and research in the field. This review focuses on the pharmacomicrobiome in transplantation. Alterations in the microbiome in transplant recipients are well documented, largely because of prophylactic antibiotic use, and the potential for DMI is high. There is evidence that the gut microbiome may alter the pharmacokinetic disposition of tacrolimus and result in microbiome-specific tacrolimus metabolites. The gut microbiome also impacts the enterohepatic recirculation of mycophenolate, resulting in substantial changes in pharmacokinetic disposition and systemic exposure. The mechanisms of these DMI and the specific bacteria or communities of bacteria are under investigation. There are little or no human DMI data for cyclosporine A, corticosteroids, and sirolimus. The available evidence in transplantation is limited and driven by small studies of heterogeneous designs. Larger clinical studies are needed, but the potential for future clinical application of the pharmacomicrobiome in avoiding poor outcomes is high.

Gut microbiome modulates tacrolimus pharmacokinetics through the transcriptional regulation of ABCB1

BACKGROUND

Following solid organ transplantation, tacrolimus (TAC) is an essential drug in the immunosuppressive strategy. Its use constitutes a challenge due to its narrow therapeutic index and its high inter- and intra-pharmacokinetic (PK) variability. As the contribution of the gut microbiota to drug metabolism is now emerging, it might be explored as one of the factors explaining TAC PK variability. Herein, we explored the consequences of TAC administration on the gut microbiota composition. Reciprocally, we studied the contribution of the gut microbiota to TAC PK, using a combination of in vivo and in vitro models.

RESULTS

TAC oral administration in mice resulted in compositional alterations of the gut microbiota, namely lower evenness and disturbance in the relative abundance of specific bacterial taxa. Compared to controls, mice with a lower intestinal microbial load due to antibiotics administration exhibit a 33% reduction in TAC whole blood exposure and a lower inter-individual variability. This reduction in TAC levels was strongly correlated with higher expression of the efflux transporter ABCB1 (also known as the p-glycoprotein (P-gp) or the multidrug resistance protein 1 (MDR1)) in the small intestine. Conventionalization of germ-free mice confirmed the ability of the gut microbiota to downregulate ABCB1 expression in a site-specific fashion. The functional inhibition of ABCB1 in vivo by zosuquidar formally established the implication of this efflux transporter in the modulation of TAC PK by the gut microbiota. Furthermore, we showed that polar bacterial metabolites could recapitulate the transcriptional regulation of ABCB1 by the gut microbiota, without affecting its functionality. Finally, whole transcriptome analyses pinpointed, among others, the Constitutive Androstane Receptor (CAR) as a transcription factor likely to mediate the impact of the gut microbiota on ABCB1 transcriptional regulation.

CONCLUSIONS

We highlight for the first time how the modulation of ABCB1 expression by bacterial metabolites results in changes in TAC PK, affecting not only blood levels but also the inter-individual variability. More broadly, considering the high number of drugs with unexplained PK variability transported by ABCB1, our work is of clinical importance and paves the way for incorporating the gut microbiota in prediction algorithms for dosage of such drugs. Video Abstract.

Intestinal Permeability in Patients Early after Kidney Transplantation Treated with Two Different Formulations of Once-Daily Tacrolimus

Adequate tacrolimus blood exposure is crucial in the early post-renal transplant period and a gut epithelial barrier integrity may play a role. We prospectively investigated several markers of intestinal permeability in recent kidney transplant recipients (KTRs) treated with different tacrolimus extended-release formulations. Within each of the 49 KTR pairs that received grafts from the same donor, an early randomized conversion was performed from twice-daily (Prograf) to once-daily tacrolimus formulation: Advagraf or Envarsus. Plasma zonulin, calprotectin, circulating lipopolysaccharide (LPS), LPS-binding protein (LBP), intestinal fatty acid binding protein (FABP-2), and CD-14 levels were measured. There was no difference in the recipient age, dialysis vintage, BMI, and residual diuresis between Advagraf and Envarsus groups. FABP-2 and LPS levels were significantly associated with tacrolimus trough level, 3-h level, and area under the curve (AUC) in the Envarsus but not in the Advagraf group. AUC was independently increased by LPS and decreased by age, FABP-2 concentration, and the use of Envarsus formulation as compared with Advagraf. Functional changes of gastrointestinal tract in patients treated with Envarsus may influence intestinal tacrolimus absorption to a greater extent than in Advagraf-treated KTRs and may lead to inadequate variability of tacrolimus exposure early after kidney transplantation.

[Pharmacokinetic changes related to acute infection. Examples from the SARS-CoV-2 pandemic]

The knowledge of factors of pharmacokinetic variability is important in order to personalize pharmacological treatment, particularly for drugs with a narrow therapeutic range for which pharmacological therapeutic monitoring is recommended. Inflammation is a protective response against acute infections and injuries that contributes to intra- and inter-individual variability in drug exposure by modulating the activity of enzymes involved in drug metabolism, and by altering the binding of drugs to plasma proteins. The understanding of the impact of inflammation on drug metabolism and the related clinical consequences allow to better take into consideration the effect of inflammation on the variability of drug exposure. We first summarized the molecular mechanisms by which inflammation contributes to the inhibition of drug metabolism enzymes. We then presented an updated overview of the consequences of the outcome of acute infectious event on pharmacokinetic exposure of drugs with a narrow therapeutic range and that are substrates of cytochrome P450, and the related clinical consequences. Finally, in the context of the COVID-19 pandemic, we reported examples of drug overexposures in COVID- 19 infected patients.

Predictors of tacrolimus pharmacokinetic variability: current evidences and future perspectives

INTRODUCTION

In kidney transplantation, tacrolimus (TAC) is at the cornerstone of current immunosuppressive strategies. Though because of its narrow therapeutic index, it is critical to ensure that TAC levels are maintained within this sharp window through reactive adjustments. This would allow maximizing efficiency while limiting drug-associated toxicity. However, TAC high intra- and inter-patient pharmacokinetic (PK) variability makes it more laborious to accurately predict the appropriate dosage required for a given patient.

AREAS COVERED

This review summarizes the state-of-the-art knowledge regarding drug interactions, demographic and pharmacogenetics factors as predictors of TAC PK. We provide a scoring index for each association to grade its relevance and we present practical recommendations, when possible for clinical practice.

EXPERT OPINION

The management of TAC concentration in transplanted kidney patients is as critical as it is challenging. Recommendations based on rigorous scientific evidences are lacking as knowledge of potential predictors remains limited outside of DDIs. Awareness of these limitations should pave the way for studies looking at demographic and pharmacogenetic factors as well as gut microbiota composition in order to promote tailored treatment plans. Therapeutic approaches considering patients' clinical singularities may help allowing to maintain appropriate concentration of TAC.

Multi-organism gastrointestinal polymerase chain reaction positivity among pediatric transplant vs non-transplant populations: A single-center experience

BACKGROUND

Diarrhea is a common problem in the pediatric post-solid organ transplant and post-hematopoietic stem cell transplant populations. Infectious etiology incidences are poorly defined, and the possibility of multi-organism positivity is often uninvestigated. The aim of this study is to utilize stool multiplex GIP assays to compare the PTP and NTP regarding the incidence and profiles of single-organism and multi-organism infectious diarrhea.

METHODS

A single-center retrospective review was conducted, investigating stool multiplex GIP panel results over a more than 3-year period, for pediatric patients. Assays test for 23 viral, bacterial, and protozoal organisms.

RESULTS

Positive assays in the PTP and NTP were 70/101 (69.3%) and 962/1716 (56.1%), respectively (P = .009). Thirty-two percent (32/101) of assays within the PTP were multi-organism positive, significantly more than 14.8% (254/1716) in the NTP (P < .00001). There was no significant difference in the incidence of single-organism positives, 37.6% (38/101) in PTP and 41.3% (708/1716) in the NTP. The PTP demonstrated a statistically significantly higher incidence of the following organisms within multi-agent positive GIPs (P < .05 for each): Clostridioides difficile, Cryptosporidium, EPEC, norovirus, and sapovirus.

CONCLUSIONS

The pediatric PTP demonstrates higher incidence of positive GIPs, higher rate of multi-organism positivity, and unique infectious organism incidence profiles. These data can provide a framework for understanding organism-specific pathogenicity factors, assessing the clinical impact of enteric co-infection, and understanding the utility of this testing modality in this unique population.

Impacts of High Intra- and Inter-Individual Variability in Tacrolimus Pharmacokinetics and Fast Tacrolimus Metabolism on Outcomes of Solid Organ Transplant Recipients

Tacrolimus is a first-line calcineurin inhibitor (CNI) and an integral part of the immunosuppressive strategy in solid organ transplantation. Being a dose-critical drug, tacrolimus has a narrow therapeutic index that necessitates periodic monitoring to maintain the drug’s efficacy and reduce the consequences of overexposure. Tacrolimus is characterized by substantial intra- and inter-individual pharmacokinetic variability. At steady state, the tacrolimus blood concentration to daily dose ratio (C/D ratio) has been described as a surrogate for the estimation of the individual metabolism rate, where a low C/D ratio reflects a higher rate of metabolism. Fast tacrolimus metabolism (low C/D ratio) is associated with the risk of poor outcomes after transplantation, including reduced allograft function and survival, higher allograft rejection, CNI nephrotoxicity, a faster decline in kidney function, reduced death-censored graft survival (DCGS), post-transplant lymphoproliferative disorders, dyslipidemia, hypertension, and cardiovascular events. In this article, we discuss the potential role of the C/D ratio in a noninvasive monitoring strategy for identifying patients at risk for potential adverse events post-transplant.

Inflammation is a major regulator of drug metabolizing enzymes and transporters: Consequences for the personalization of drug treatment

Inflammation is an evolutionary process that allows survival against acute infection or injury. Inflammation is also a pathophysiological condition shared by numerous chronic diseases. In addition, inflammation modulates important drug-metabolizing enzymes and transporters (DMETs), thus contributing to intra- and interindividual variability of drug exposure. A better knowledge of the impact of inflammation on drug metabolism and its related clinical consequences would help to personalize drug treatment. Here, we summarize the kinetics of inflammatory mediators and the underlying transcriptional and post-transcriptional mechanisms by which they contribute to the inhibition of important DMETs. We also present an updated overview of the effect of inflammation on the pharmacokinetic parameters of most of the drugs that are DMET substrates, for which therapeutic drug monitoring is recommended. Furthermore, we provide opinions on how to integrate the inflammatory status into pharmacogenetics, therapeutic drug monitoring, and population pharmacokinetic strategies to improve the personalization of drug treatment for each patient.

Clinically useful limited sampling strategy to estimate area under the concentration-time curve of once-daily tacrolimus in adult Japanese kidney transplant recipients

BACKGROUND

An extended-release, once-daily, oral formulation of tacrolimus is currently used after kidney transplantation as a substitute for the conventional twice-daily formulation. The purpose of this study was to provide a limited sampling strategy with minimum and optimum sampling points to predict the tacrolimus area under the concentration-time curve (AUC) after administration of once-daily tacrolimus in de novo adult kidney transplant patients.

METHODS

A total of 36 adult Japanese kidney transplant patients receiving once-daily tacrolimus were included: 31 were allocated to a study group to develop limited sampling strategy (LSS) model equations based on multiple stepwise linear regression analysis, and 5 were allocated to a validation group to estimate the precision of the LSS equations developed by the study group. Twelve-hour AUC (AUC0-12) was calculated by the trapezoidal rule, and the relationship between individual concentration points and AUC0-12 were determined by multiple linear regression analysis. The coefficient of determination (R2) was used to assess the goodness-of-fit of the regression models. Three error indices (mean error, mean absolute error, and root mean squared prediction error) were calculated to evaluate predictive bias, accuracy, and precision, respectively. Quality of the statistical models was compared with Akaike's information criterion (AIC).

RESULTS

A four-point model using C0, C2, C4 and C6 gave the best fit to predict AUC0-12 (R2 = 0.978). In the three- and two-point models, the best fits were at time points C2, C4, and C6 (R2 = 0.973), and C2 and C6 (R2 = 0.962), respectively. All three models reliably estimated tacrolimus AUC0-12, consistent with evaluations by the three error indices and Akaike's information criterion. Practically, the two-point model with C2 and C6 was considered to be the best combination, providing a highly accurate prediction and the lowest blood sampling frequency.

CONCLUSIONS

The two-point model with C2 and C6 may be valuable in reducing the burden on patients, as well as medical costs, for once-daily tacrolimus monitoring.

Immunologic Risk Assessment and Approach to Immunosuppression Regimen in Kidney Transplantation

The outcomes of kidney transplantation show a steady improvement with an increasing number of transplantations and decreasing incidence of acute rejection episodes. Successful transplantation begins with a comprehensive immunologic risk assessment and judicious choice of therapeutic agents. In this review, we discuss the trends in transplant immunosuppression practices and outcomes in the United States. We discuss practical testing algorithms for clinical decision making in induction therapy and fine-tuning maintenance immunosuppression. We introduce assessment tools for immune monitoring after transplantation and speculate on future directions in management.

Reduction of exposure to tacrolimus trough level variability is associated with better graft survival after kidney transplantation

PURPOSE

High tacrolimus trough drug level variability was found to be associated with reduced graft survival. The primary goal of this study was to find whether reduction of exposure to high tacrolimus trough level variability in patients in which previously had high variability was associated with better graft survival.

METHODS

All tacrolimus drug level values in patients that underwent kidney transplantation at our center between 2006 and 2015 were collected. Exposure to variability was calculated using a time-weighted coefficient of variability (TWCV). Time-dependent univariate and multivariate Cox proportional hazard models were used to analyze the primary outcome of graft survival and to determine a cutoff value for TWCV as a predictor of this outcome.

RESULTS

A total of 878 patients were included in the study with a median follow-up of 1263 days. TWCV above 25% was significantly associated with reduced graft survival (HR3.66, 95% CI 2.3-5.8, p < 0.001). Of the 480 patients (54.7%) who had a cumulative TWCV of > 25% at a certain time during the follow-up, 110 (22.9%) later returned to a cumulative TWCV of less than 25%. Reduction of TWCV to values below 25% was associated with a hazard of graft loss that was not different from patients who had cumulative TWCV of less than 25% during the entire follow-up period (HR 1.81, 95% CI 0.71-4.62, p = 0.218 and HR 1.08, 95% CI 0.39-2.99, p = 0.780) in univariate and multivariate analyses, respectively.

CONCLUSIONS

Monitoring TWCV can help detect the high-risk patients. Interventions intended to reduce variability on long-term graft survival may have a positive effect on graft survival.

Association of the combination of time-weighted variability of tacrolimus blood level and exposure to low drug levels with graft survival after kidney transplantation

Background

The variability of tacrolimus blood levels has been shown to be associated with inferior graft survival. However, the effect of variability during the early post-transplantation period has not been evaluated. We sought to evaluate the association between time-weighted variability in the early post-transplantation period and graft survival. We also explored the interaction between drug level variability and exposure to inadequate drug levels.

Methods

This retrospective cohort study included all patients who underwent kidney transplantation in the Rabin Medical Center and were treated with tacrolimus. Time-weighted coefficient of variability (TWCV) was defined as time-weighted standard deviation divided by the mean drug level. Univariate and multivariate Cox proportional hazard model was used with the primary outcome of patients and graft survival.

Results

The study population included 803 patients who underwent kidney transplantation between 1 January 2000 and 29 September 2013. The high tertile of TWCV of tacrolimus blood levels was associated with reduced graft survival by univariate and multivariate analyses [hazard ratio (HR) 1.69, 95% confidence interval (CI) 1.14-2.53, P = 0.01 and HR 1.74, 95% CI 1.14-2.63, P = 0.01, respectively]. The interaction between high TWCV and exposure to inadequately low drug levels was significantly associated with reduced survival (P = 0.004), while the interaction between TWCV and high drug blood levels was not. One hundred and thirty patients (16.2%) had the combination of high TWCV and exposure to low drug values (<5 ng/mL). These patients had reduced graft survival by univariate and multivariate analyses (HR 2.42, 95% CI 1.57-3.74, P < 0.001 and HR 2.6, 95% CI 1.65-4.11, P < 0.001, respectively).

Conclusions

The combination of high TWCV and exposure to low drug levels might identify high-risk patients in the early post-transplantation period.

Influence of tacrolimus metabolism rate on renal function after solid organ transplantation

The calcineurin inhibitor (CNI) tacrolimus (TAC) is an integral part of the immunosuppressive regimen after solid organ transplantation. Although TAC is very effective in prevention of acute rejection episodes, its highly variable pharmacokinetic and narrow therapeutic window require frequent monitoring of drug levels and dose adjustments. TAC can cause CNI nephrotoxicity even at low blood trough levels (4-6 ng/mL). Thus, other factors besides the TAC trough level might contribute to CNI-related kidney injury. Unfortunately, TAC pharmacokinetic is determined by a whole bunch of parameters. However, for daily clinical routine a simple application strategy is needed. To address this problem, we and others have evaluated a simple calculation method in which the TAC blood trough concentration (C) is divided by the daily dose (D). Fast TAC metabolism (C/D ratio < 1.05) was identified as a potential risk factor for an inferior kidney function after transplantation. In this regard, we recently showed a strong association between fast TAC metabolism and CNI nephrotoxicity as well as BKV infection. Therefore, the TAC C/D ratio may assist transplant clinicians in a simple way to individualize the immunosuppressive regimen.

Enteric-coated mycophenolate sodium given in combination with tacrolimus has a lower incidence of serious infections in Asian renal-transplant recipients compared with mycophenolate mofetil

AIMS

To compare the characteristics of the enteric-coated formulation of mycophenolate sodium (EC-MPS, myfortic) and mycophenolate mofetil (MMF, CellCept) given in combination with tacrolimus in Asian renal-transplant recipients.

METHODS

In a 24-month, single-centre, randomized, open-label, prospective study, 101 live-donor kidney transplant recipients were randomized to the EC-MPS (n = 50) or MMF (n = 51) group. The incidence of infection, therapeutic effect and adverse events were monitored.

RESULTS

The incidences of infection were 40% and 49% for the EC-MPS and MMF groups, respectively (p = 0.362). However, serious infection was only observed in the MMF group (11.8%; p = 0.027). The incidences of gastro-intestinal adverse events (GI AEs) were 24% and 41.2% for EC-MPS and MMF, respectively (p = 0.066). However, serious diarrhoea only occurred in the MMF group (9.8%; p = 0.056). The trough level of FK 506 at the time of diarrhoea (13.22 ± 3.66 ng/ml) was significantly higher than the level within 1 month before (9.18 ± 1.12 ng/ml; p < 0.05) and 1 month after diarrhoea (9.13 ± 0.85 ng/ml; p < 0.05). The infection rate of patients with diarrhoea was significantly higher than those without diarrhoea (68%, 39%, p = 0.024). The serum creatinine level was 698 ± 60 μmol/l for EC-MPS and 673 ± 68 μmol/l for MMF from baseline (p > 0.05), and it decreased to 66 ± 6 μmol/l for EC-MPS and 69 ± 8 μmol/l for MMF at 24 months (p > 0.05). The incidences of biopsy proven acute rejection (BPAR) were 20% and 25.5% for EC-MPS and MMF, respectively (p = 0.511).

CONCLUSIONS

Enteric-coated formulation of mycophenolate sodium, given in combination with tacrolimus, has a lower incidence of serious infection in Asian renal-transplant recipients compared with MMF, and the therapeutic effect of EC-MPS is similar to MMF. The clinical trial registration number is ChiCTR-IPR-14005509. The registry name is 'Effect of Enteric-coated mycophenolate sodium on posttransplant infection rate after renal transplantation compared with Mycophenolate mofetil'.

Gut microbiota and tacrolimus dosing in kidney transplantation

Tacrolimus dosing to establish therapeutic levels in recipients of organ transplants is a challenging task because of much interpatient and intrapatient variability in drug absorption, metabolism, and disposition. In view of the reported impact of gut microbial species on drug metabolism, we investigated the relationship between the gut microbiota and tacrolimus dosing requirements in this pilot study of adult kidney transplant recipients. Serial fecal specimens were collected during the first month of transplantation from 19 kidney transplant recipients who either required a 50% increase from initial tacrolimus dosing during the first month of transplantation (Dose Escalation Group, n=5) or did not require such an increase (Dose Stable Group, n=14). We characterized bacterial composition in the fecal specimens by deep sequencing of the PCR amplified 16S rRNA V4-V5 region and we investigated the hypothesis that gut microbial composition is associated with tacrolimus dosing requirements. Initial tacrolimus dosing was similar in the Dose Escalation Group and in the Stable Group (4.2±1.1 mg/day vs. 3.8±0.8 mg/day, respectively, P=0.61, two-way between-group ANOVA using contrasts) but became higher in the Dose Escalation Group than in the Dose Stable Group by the end of the first transplantation month (9.6±2.4 mg/day vs. 3.3±1.5 mg/day, respectively, P<0.001). Our systematic characterization of the gut microbial composition identified that fecal Faecalibacterium prausnitzii abundance in the first week of transplantation was 11.8% in the Dose Escalation Group and 0.8% in the Dose Stable Group (P=0.002, Wilcoxon Rank Sum test, P<0.05 after Benjamini-Hochberg correction for multiple hypotheses). Fecal Faecalibacterium prausnitzii abundance in the first week of transplantation was positively correlated with future tacrolimus dosing at 1 month (R=0.57, P=0.01) and had a coefficient±standard error of 1.0±0.6 (P=0.08) after multivariable linear regression. Our novel observations may help further explain inter-individual differences in tacrolimus dosing to achieve therapeutic levels.

Epstein-Barr virus--associated posttransplantation lymphoproliferative disorder with tacrolimus metabolism deterioration in infants after living-donor liver transplantation

BACKGROUND

Posttransplantation lymphoproliferative disorder (PTLD) in infants after liver transplantation is strongly associated with tacrolimus (Tac) administration and primary Epstein-Barr virus (EBV) transmission.

METHODS

From 1991 to 2012, 32 survivors younger than 2 years who had undergone living-donor liver transplantation using Tac for primary immunosuppression were retrospectively investigated for changes in Tac trough levels before and at the onset of posttransplantation viral infection episodes.

RESULTS

Twenty-one recipients experienced 33 viral infection episodes associated with EBV-related PTLD (n = 5), symptomatic EBV infection without development of PTLD (n = 8), and other viral infections (n = 20). Although the average Tac trough levels during the 2 months before the onset of viral infection episodes were similar among the 33 episodes (9.0 ± 2.8 ng/mL), the Tac trough levels at the onset were significantly higher in the episodes with PTLD than in those with EBV infection without the development of PTLD and with other viral infections (19.2 ± 9.0 ng/mL vs. 9.3 ± 5.2 ng/mL and 10.6 ± 5.1 ng/mL, respectively) (P<0.05). Tacrolimus trough levels at the onset of PTLD were significantly higher during the 2 months before the onset (median, 1.83 times higher than average) compared with EBV infection (1.14 times higher) and other viral infections (1.06 times higher) (P<0.05). The Tac blood concentration-to-dose ratio at the onset of PTLD was more than twice as high as the average value during the 2 months before the onset.

CONCLUSION

Deteriorated Tac metabolism accompanied by a positive change in the blood EBV DNA load may enable us to predict the development of PTLD in liver-transplanted infants with viral infection.

Effects of elevated tacrolimus trough levels in association with infectious enteritis on graft function in renal transplant recipients

BACKGROUND

The bioavailability of oral tacrolimus is influenced by enterocyte metabolism, which involves CYP3A and P-glycoprotein. Viral infection-induced intestinal inflammation damages the enterocytes and causes unfavorable elevations in blood tacrolimus levels in transplant recipients, which may lead to nephrotoxicity.

METHODS

From May 2000 to May 2011, 56 renal transplant recipients receiving tacrolimus at our hospital suffered from infectious enteritis with diarrhea. We investigated the tacrolimus trough levels before and after the onset of enteritis and evaluated the influence of elevated tacrolimus trough levels on the rate of changes in serum creatinine levels.

RESULTS

Elevated tacrolimus trough levels were observed in 52 recipients (93%) after the onset of diarrhea, and the mean value was 2.3 times higher than that before the onset of enteritis (P = .0175). Tacrolimus trough levels returned to their previous levels 2 weeks after the onset of enteritis, even in recipients with >2-fold increase, following dose adjustments. Serum creatinine levels did not significantly differ between recipients with >2-fold increase in tacrolimus trough levels and those with <2-fold increase in trough levels during a 6-month period after the onset of enteritis.

CONCLUSIONS

Elevations in the tacrolimus trough levels due to infectious enteritis with diarrhea can improve in ∼2 weeks by adjusting the tacrolimus dosage. Such temporary elevations in the tacrolimus trough levels may not produce serious nephrotoxicity even in recipients with remarkably elevated trough levels.

Tacrolimus in transplant rejection

INTRODUCTION

Renal transplantation is the best therapy for patients with end-stage renal disease. To avoid graft rejection, adequate immunosuppressive therapy is crucial. Tacrolimus is approved for prophylaxis of transplant rejection in liver, kidney or heart allograft recipients and for the treatment of allograft rejection resistant to treatment with other immunosuppressive medicinal products.

AREAS COVERED

The objective of this review is to summarize the clinical efficacy of tacrolimus in renal transplantation with special emphasis on acute rejection, refractory rejection and nephrotoxicity and post-transplant diabetes mellitus as typical adverse effects of the drug.

EXPERT OPINION

Since its approval in 1994, tacrolimus has proven its efficacy as a cornerstone of modern immunosuppressive therapy not only in numerous randomized clinical trials but also in standard clinical care. Compared with cyclosporine, the use of tacrolimus in renal transplant recipients is associated with a reduced risk for acute rejection, a reduction in the occurrence of steroid-resistant rejection and a better graft function. The avoidance of nephrotoxicity and especially post-transplant diabetes mellitus are of major interest in long-term care of renal transplant recipients.

Long-term outcome of living related renal transplantation in a patient with short bowel syndrome

Short-bowel syndrome (SBS) is defined as the malabsorptive state that occurs after extensive resection of the small intestine. In patients with SBS, oral administration of drugs usually becomes difficult because of the severity of intestinal failure. We describe a successful living related renal transplantation (LRRTx) in an 18-year-old male with SBS. Shortly after birth, the patient developed necrotizing enterocolitis requiring massive resection of the small intestine, which resulted in SBS. At seven years of age, the patient developed proteinuria and was diagnosed as focal segmental glomerulosclerosis (FSGS). His kidney function was gradually deteriorated toward the end-stage renal failure. The patient received LRRTx at age of 18 years. To evaluate the absorption capacity of the patient, we investigated pharmacokinetics of calcineurine inhibitors (tacrolimus and cyclosporine). The drug concentration, which is sufficient to provide effective immunosuppression, was achieved with cyclosporine, but not with tacrolimus. The patient therefore received a triple immunosuppressive therapy with oral cyclosporine, methyl-prednisolone and mycophenolate mofetil. To prevent both recurrent FSGS and rejection, we repeatedly analyzed the trough level and the pharmacokinetics of cyclosporine after LRRTx. The patient was successfully treated with oral immunosuppression for over 5 years, without hemodialysis. To our knowledge, this is the first report showing the long-term outcome of LRRTx treated with oral cyclosporine in a patient with SBS.

Tacrolimus nephrotoxicity: beware of the association of diarrhea, drug interaction and pharmacogenetics

Tacrolimus is known to potentially lead to adverse events in recipients with diarrhoea and/or calcium channel blocker (CCB) co-administration. We report a renal transplant recipient who suffered from severe nephrotoxicity related to a toxic tacrolimus trough concentration in both conditions, diarrhoea and CCB co-administration, and with genotyped CYP3A system and P-glycoprotein (P-gp) polymorphisms. To our knowledge, this is the first case to be investigated for such polymorphisms. Clinicians should be reminded of the possibility of highly increased levels of tacrolimus in situations of diarrhoea and/or co-administration of CCBs. It also highlights the key role in tacrolimus pharmacokinetics of the CYP3A system and P-gp polymorphisms, and their influence in high-risk situations when enzyme activity is already affected by enterocyte damage due to diarrhoea and CCB competition.

Immunosuppression armamentarium in 2010: mechanistic and clinical considerations

Effective immunosuppression is the key to successful organ transplantation, with success being defined as minimal rejection risk with concomitant minimal drug toxicities. Despite the general recognition of this fact, a paucity of appropriate clinical trials in children has contributed to lack of standardization of clinical management regimens, resulting in an extensive diversity of favored approaches. Nonetheless, although consensus has not been reached on the ideal approach to immunosuppression in pediatric transplantation, new drug therapies have contributed to a continuing improvement in graft and patient survival. Future clinical research must focus on diminishing the extensive burden of toxicities of these therapeutic agents in children.

Conversion from mycophenolate mofetil to delayed formulation in pediatric renal transplantation: higher mycophenolic acid predose level but no changes in the immune biomarkers

EC-MPS was designed to improve MPA-related GII because of MMF, by delaying the release of MPA until reaching the small intestine. At present, its immunosuppressive activity in pediatric renal transplant recipients with GII has not been clarified. We studied eight renal transplant recipients before and after three months of the conversion from MMF to equimolar doses of EC-MPS. After three months of treatment with EC-MPA, GII decreased between 100% and 12.5%. The predose levels of MPA were about 60% higher on EC-MPS (6.9 +/- 1.1 microg/mL) compared with MMF administration (4.2 +/- 0.9 microg/mL). Hemoglobin decreased significantly post-conversion (12.0 +/- 0.4 to 11.0 +/- 0.5 g/dL). Serum creatinine, creatinine clearance, and urinary protein excretion did not change. Also, proliferative response and cytotoxic antibodies showed no significant change. The release of interleukin-10 was strikingly augmented with MMF or EC-MPS therapy; meanwhile, gamma-interferon and TNF were low under both treatments. Our data indicate that conversion from MMF to EC-MPS leads to an improvement in GII without altering key elements of immunosuppression.

Severe diarrhea in renal transplant patients: results of the DIDACT study

Diarrhea is common in transplant recipients. While the majority of cases are mild and transient, some are severe and prolonged, which can threaten graft survival through dehydration. While it is known that some immunosuppressive agents can elicit diarrhea, there does not appear to be any consensus on the role that other nonimmunosuppressive causes can play in transplant patients. The aim of the present open, nonrandomized, multicenter study was to identify nonimmunosuppressive factors involved in severe diarrhea in renal transplant patients. Patients (n = 108) with severe diarrhea (>/=3 stools/day for >/=7 days) were enrolled from 16 Belgian transplant centers. Patients were diagnosed according to an agreed flowchart that consisted of identification of possible infections, followed by changes in empirical and immunosuppressive treatment. Approximately 50% of patients experienced resolution of severe diarrhea following treatment for infections, dietary problems or diarrhea-causing concomitant medications. In conclusion, a large proportion of the severe diarrhea observed in renal transplant recipients is not associated with immunosuppressive therapy and can be treated through anti-infectives, changes to concomitant medication and other empirical treatments. Correct diagnosis of the cause of severe diarrhea in such patients should help to protect graft survival in transplant recipients.