Increased tacrolimus levels during diarrhea

SARS-CoV-2 Infection Can Lead to an Increase in Tacrolimus Levels in Renal Transplant Patients: A Cohort Study

The aim of this study is to evaluate the effect of SARS-CoV-2 infection on serum tacrolimus levels. Tacrolimus levels of 34 transplant patients diagnosed with SARS-CoV-2 in 2020 were compared with their pre-infection values and those of a control group with alternative infections. 20 out of 34 (59%) had high levels. At diagnosis, median tacrolimus level in the SARS-CoV-2 cohort was 9.6 μg/L (2.7-23) compared to 7.9 μg/L in the control group (p = 0.07, 95% CI for difference -0.3-5.8). The ratio of post-infection to pre-infection tacrolimus values was higher in the SARS-CoV-2 group (1.7) compared to the control group (1.25, p = 0.018, 95% CI for difference 0.08-0.89). The acute kidney injury rate was 65% (13 of 20) in SARS-CoV-2 patients with a level >8 μg/dl, compared to 29% (4 of 14) in those with lower levels (p = 0.037). Median length of stay was 10 days among SARS-CoV-2 infected patients with high tacrolimus levels compared to 0 days in the rest (p = 0.04). Four patients with high levels died compared to 2 in the control group. Clinicians should be aware of this potential effect on tacrolimus levels and take appropriate measures.

Sex differences in transplantation

Sex plays a role in the incidence and progression of a wide variety of diseases and conditions related to transplantation. Additionally, a growing body of clinical and experimental evidence suggests that sex can impact the pharmacokinetics and pharmacodynamics of several commonly used immunosuppressive and anti-infective drugs in transplant recipients. A better understanding of these sex differences will facilitate advances in individualizing treatment for patients and improve outcomes of solid organ transplantation. Here, we provide a review of sex-related differences in transplantation and highlight opportunities for future research directions.

Tacrolimus Pharmacokinetic and Pharmacogenomic Differences between Adults and Pediatric Solid Organ Transplant Recipients

Tacrolimus is a calcineurin inhibitor immunosuppressant that has seen considerable use in both adult and pediatric solid organ transplant recipients. Though there is much pharmacokinetic data available for tacrolimus in the adult population, the literature available for children is limited. Furthermore, very little is known about the pharmacogenomic differences in the two patient groups. Based on what information is currently available, clinically significant differences may exist between the two populations in terms of absorption, distribution, metabolism and elimination. In addition, inherent physiological differences exist in the young child including: less effective plasma binding proteins, altered expression of intestinal P-glycoprotein, and increased expression of phase 1 metabolizing enzymes, therefore one would expect to see clinically significant differences when administering tacrolimus to a child. This paper examines available literature in an attempt to summarize the potential pharmacokinetic and pharmacogenomic variability that exists between the two populations.

A cluster of rotavirus enteritis in adult transplant recipients

Diarrhea following solid organ transplantation is a common side effect of some immunosuppressive agents but can also be caused by many pathogens. An outbreak of rotavirus (RV) enteritis presenting with severe diarrhea in four solid organ recipients was analyzed. The first case was diagnosed in a 6-month-old liver recipient who was prehospitalized on a pediatric ward. Within 1 month, three adult patients (two liver, one renal recipient) presented with enteritis. During diarrhea a significant rise in tacrolimus levels was observed. One patient developed toxic megacolon with ulcerative colitis. Infections were self-limiting but led to secondary infectious complications and prolonged hospitalization. This is the first reported outbreak of RV enteritis in a multiorgan transplant unit involving adult patients. Although no fingerprinting or subtyping of the virus was performed we assume the child was the primary source. In transplant recipients presenting with diarrhea RV infection should be considered.

Minimization of immunosuppressive therapy after renal transplantation: results of a randomized controlled trial

Modern immunosuppressive regimens reduce the acute rejection rate by combining a cornerstone immunosuppressant like tacrolimus or cyclosporine with adjunctive agents like corticosteroids, mycophenolate mofetil (MMF) or azathioprine, often associated with untoward side effects. A 6-month randomized study was conducted in 47 European centers. Triple therapy with tacrolimus (trough levels 5-15 ng/mL), corticosteroids (dosage 10 mg/day) and MMF (1 g/day) was administered for 3 months. From day 92, patients either continued with triple therapy (control, n = 277), or stopped steroids (n = 279), or stopped MMF (n = 277). Surrogate markers for long-term benefits were changes in lipid profiles and occurrence of hematological, gastrointestinal and infectious complications. The 6-month acute rejection incidence (biopsy-proven) was similar in all groups (17.0% vs. 15.1% vs. 14.8%, p = 0.744), although the incidence after month 3 was higher in the steroid stop group than in the two other groups. Mean reductions in total cholesterol (18.9 mg/dL [0.49 mmol/L]) and LDL-cholesterol (8.1 mg/dL [0.21 mmol/L]) between months 4 and 6 were greater in the steroid stop group (p < 0.001). Leukopenia (p = 0.0082), serious CMV infection (p = 0.024), anemia (p = NS) and diarrhea (p = NS) were less frequent in the MMF stop group. In a study population of immunologically low-risk patients' withdrawal of corticosteroids or MMF from a tacrolimus-based therapy at 3 months was feasible. A longer follow-up will be needed to confirm the expected advantages for the long-term outcome and to assess the long-term safety of this minimization of immunosuppressive therapy.

Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation

The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immunosuppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.

Time-related clinical determinants of long-term tacrolimus pharmacokinetics in combination therapy with mycophenolic acid and corticosteroids: a prospective study in one hundred de novo renal transplant recipients

BACKGROUND

Tacrolimus is an efficient primary immunosuppressive drug in renal transplantation but its long-term use is associated with calcineurin-inhibitor-related toxicity. The specific characteristics of the inter-relationship between dose, concentration and clinical (side-)effects for tacrolimus have not yet been identified and extensive long-term pharmacokinetic studies are presently lacking.

OBJECTIVE

To establish the characteristics of the long-term pharmacokinetics of tacrolimus, to determine the time-dependent factors that influence the pharmacokinetics within the first critical post-transplant year and to identify a more appropriate way of monitoring drug exposure in clinical practice.

STUDY DESIGN

A prospective pharmacokinetic study of tacrolimus was conducted in 100 de novo renal allograft recipients during the first year post-transplantation.

METHODS

Area under the concentration-time curve (AUC) blood samplings for tacrolimus were performed on days 7, 42, 90, 180 and 360 for all patients. Model-independent pharmacokinetic parameters for tacrolimus were calculated and dose-corrected when appropriate: AUC12, peak plasma concentration (Cmax), pre-dose trough concentration (C0), time to Cmax, average steady-state blood concentration, steady-state total body clearance, terminal half-life, volume of distribution and an estimate for tacrolimus bioavailability was derived from additional steady-state intravenous clearance data. The association between tacrolimus pharmacokinetic parameters and different clinical variables was evaluated on days 7, 42, 90, 180 and 360. The clinical variables were either donor-related (e.g. donor age), transplantation-related (e.g. delayed graft function), recipient-related (e.g. bodyweight), biochemical (e.g. serum albumin), therapeutic variables (e.g. corticosteroid dose) or disease variables (e.g. liver dysfunction).

RESULTS

Long-term tacrolimus dose-corrected exposure (AUC12, C0) is characterised by a late significant increase towards the end of the first year post-transplantation as the result of a significant increase in tacrolimus bioavailability (p < 0.05) and a slow decrease in tacrolimus steady-state clearance. Consequently, tacrolimus dose-requirements corrected for bodyweight decrease significantly in the first postoperative year (p < 0.05), in part because of the simultaneous tapering of the corticosteroid dose which significantly affects tacrolimus bioavailability (p < 0.05). Other clinical variables that significantly influenced tacrolimus administration, exposure and bioavailability in a time-related fashion were identified in this study (renal allograft function [p < 0.05], liver dysfunction [p < 0.05], diarrhoea [p < 0.05]), while the clinical relevance of other variables was considerably moderated by our findings (serum albumin, haematocrit). Time-unrelated variables proved to be of significant continuing clinical importance for tacrolimus dose-exposure pharmacokinetics throughout the first post-transplant year (recipient age [p < 0.05], gender [p < 0.01] and donor-receptor gender mismatch [p < 0.05]), while donor hypotension (p < 0.05) and cold ischaemia time (p < 0.05) also proved significant although at present the reasons for this are unknown. Finally, using multiple stepwise regression analysis we demonstrated that classical assessment of tacrolimus exposure by monitoring pre-dose trough blood concentration (or any other single concentration sampling timepoint) is not the most reliable method and that abbreviated AUC measurements may constitute a more accurate clinical tool for (therapeutic) monitoring of drug exposure.

CONCLUSION

Tacrolimus pharmacokinetics in the first year after renal transplantation are characterised by a specific time-dependent evolution. The identification of clinical variables that determine tacrolimus pharmacokinetics is an important aid in the development of reliable drug monitoring strategies using abbreviated AUC measurements.