Tacrolimus Concentration in Saliva of Kidney Transplant Recipients: Factors Influencing the Relationship with Whole Blood Concentrations

Objective: The objective of this study was to examine the association between tacrolimus concentration in oral fluids and in whole blood and to investigate the various factors that influence this relationship. Patients and Methods: Forty-six adult kidney transplant recipients were included in the study. Study A (ten patients) included the collection of several paired oral fluid samples by passive drool over a 12-h post-dose period. Study B (36 patients) included the collection of oral fluids pre-dose and at 2 h after the tacrolimus dose under three conditions: un-stimulated, after stimulation with a tart candy, and after mouth rinsing. The tacrolimus concentration in oral fluids was measured by a specially developed sensitive and specific liquid chromatography mass spectrometry method. A salivary transferrin concentration of \u3e1 mg/dL was used as a cut-off value for oral fluid blood contamination. Results: Rinsing the oral cavity before sampling proved to provide the most suitable sampling strategy giving a correlation coefficient value of 0.71 (p = 0.001) between the tacrolimus concentration in oral fluids and the tacrolimus concentration in whole blood at trough. Mean and 95% confidence interval of tacrolimus concentration in oral fluids at the pre-dose concentration for samples collected after mouth rinsing was 584 (436, 782) pg/mL. The ratio of the tacrolimus concentration in oral fluids to the tacrolimus concentration in whole blood (*100) was 11% (95% confidence interval 9–13) for all sampling times. Oral fluid pH or weight of a saliva sample did not influence the tacrolimus concentration in oral fluids. Tacrolimus distribution into oral fluids exhibited a delay with a pronounced counter-clockwise hysteresis with respect to the time after dose. A multivariate analysis of variance revealed that the tacrolimus concentration in oral fluids is related to the tacrolimus concentration in whole blood and tacrolimus plasma-binding proteins including albumin and cholesterol. Conclusion: An optimal sampling strategy for the determination of the tacrolimus concentration in oral fluids was established. Measuring the tacrolimus concentration in oral fluids appears to be a feasible and non-invasive method for predicting the concentration of tacrolimus in whole blood

Inosine monophosphate dehydrogenase expression and activity are significantly lower in kidney transplant recipients with diabetes mellitus

Background: Inosine 50-monophosphate dehydrogenase (IMPDH) is a target of the immunosuppressive drug, mycophenolic acid (MPA). A 12-hour clinical pharmacokinetic and pharmacodynamic study was conducted to compare IMPDH1 and IMPDH2 gene expression, IMPDHI and IMPDHII protein levels, and enzyme activity between kidney transplant recipients with respect to diabetes status. Methods: Nondiabetic (ND, n = 11) and diabetic (D, n = 9) kidney transplant recipients and on nontransplant nondiabetic (n = 10) and diabetic (n = 10) volunteers were included in the study. Results: Area under the effect curve values for gene expression: IMPDH1 [ND: 22.1 (13.8-31.3) versus D: 4.5 (2.3-6.5), P\u3e0.001] and IMPDH2 [ND: 15.3 (11.0-21.7) versus D: 6.1 (4.6-8.6), P\u3e 0.001], protein level: IMPDHI [ND: 1.0 (0.5-1.3) versus 0.5 (0.4- 0.7), P = 0.002] and IMPDHII [ND: 1.0 (0.6-1.6) versus D: 0.7 (0.6-0.8) P\u3e0.001] and enzyme activity [ND: 180 (105-245) versus D: 29.9 (15.3-35.6) mmole$s21$mole21 adenosine monophosphate, P\u3e0.001] was significantly lower in transplant recipients with diabetes. Similar results were observed in nontransplanted volunteers. Kinetic studies of MPA-mediated suppression of IMPDH activity in nontransplanted individuals revealed an approximately 2.5-fold lower half-maximum effective concentration (EC50) for diabetic as compared with nondiabetic [ND: 50.2 (49.8-50.7) versus D: 15.8 (15.6-16.3) nmole/L, P = 0.004] volunteers. This difference was not related to several IMPDH gene variants. Conclusions: This study indicates a significantly lower IMPDH gene expression, protein level, and enzyme activity in diabetic patients. Further clinical studies in a larger number of patients are warranted to verify whether MPA dosing must be optimized for kidney transplant recipients with diabetes mellitus. © 2013 by Lippincott Williams and Wilkins

Blood and plasma pharmacokinetics of ciclosporin in diabetic kidney transplant recipients

Background and objectives: Long-term diabetes mellitus may affect the absorption, distribution and metabolism of immunosuppressive agents used after organ transplantation. The aims of this study were to characterize ciclosporin pharmacokinetics in blood and plasma and to compare the ciclosporin unbound concentration and the blood : plasma concentration (B : P) ratio in diabetic kidney transplant recipients. Patients and methods: Ciclosporin 12-hour steady-state pharmacokinetics were studied in eight diabetic and nine nondiabetic patients. Ciclosporin concentrations in whole blood and in plasma were measured using liquid chromatography-tandem mass spectrometry, and the ciclosporin fraction unbound (fu) was determined by an equilibrium dialysis method utilizing [3H]ciclosporin as a tracer. Oral absorption of paracetamol (acetaminophen) was used as a marker for gastric emptying. Results: In diabetic patients, the time to the peak blood ciclosporin concentration at steady state (tmax,ss) was prolonged (128 minutes vs 93 minutes in nondiabetic patients, p \u3c 0.01) and, on average, the paracetamol tmax was prolonged by 30 minutes. The whole-blood dose-normalized area under the concentration-time curve from 0 to 12 hours (AUC12) was marginally lower in diabetic patients (p = 0.09) and the plasma AUC12 was significantly lower (p = 0.03). The ciclosporin fu was numerically higher in diabetic patients (1.20 ± 0.65% vs 0.72 ± 0.28% in nondiabetic patients, p = 0.066); however, the unbound concentration values were essentially similar in the two groups (0.58 ± 0.76 μg/L in diabetic patients and 0.52 ± 0.48 μg/L in nondiabetic patients; p = 0.59). No difference was observed in the ciclosporin B : P ratio between the two groups. Conclusion: This study indicates that diabetes delays ciclosporin absorption, reduces ciclosporin exposure and increases the ciclosporin fu but not the pharmacologically active unbound concentration. © 2008 Adis Data Information BV. All rights reserved

Analysis of mycophenolic acid in saliva using liquid chromatography tandem mass spectrometry

Salivary levels of the immunosuppressive agent, mycophenolic acid (MPA), may provide a convenient and noninvasive method for drug monitoring. An analytical method was developed and validated for quantification of salivary MPA using liquid chromatography tandem mass spectrometry. Sample preparation included addition of 50 μL internal standard solution [500 μg/L indomethacin in methanol] to 100 μL saliva sample, followed by protein precipitation with 200 μL acetonitrile. Supernatants were dried and reconstituted in 100 μL of 85:15% (vol/vol) mixture of methanol and water containing 0.05% formic acid and 20 μL was injected onto the analytical column. The mobile phase comprised a gradient mixture of methanol and 0.05% formic acid, giving a total run time of 7.5 minutes. Chromatograms were obtained using mass transitions of m/z 319.0→190.8 for MPA and m/z 355.9→312.2 for indomethacin. The calibration curve was linear over a concentration range of 2.5 to 800 μg/L (r=0.9999) and the recovery of MPA from saliva was \u3e90%. The inaccuracy was \u3c10% and intra- and interday coefficient of variation ranged from 2.8% to 5.2%. Mean±SD of MPA concentrations in saliva (n=100) obtained from 11 kidney transplant recipients was 31.4±32.3 μg/L (range: 2.6 to 220.4 μg/L) and correlated well with total (r=0.909) and unbound (r=0.910) MPA concentrations in plasma. In conclusion, a simple, sensitive, and specific method was developed and validated for quantification of MPA in saliva. Additional clinical studies are required to establish the usefulness of this specimen in the clinical management of organ transplant recipients. Copyright © 2006 by Lippincott Williams & Wilkins

Tacrolimus in diabetic kidney transplant recipients: Pharmacokinetics and application of a limited sampling strategy

The effect of diabetes mellitus on the pharmacokinetics of tacrolimus is not well characterized. We have compared tacrolimus 12-hour steady-state concentration-time profiles in diabetic (n = 11) and demographically matched nondiabetic (n = 9) stable kidney transplant recipients and derived a limited sampling strategy for the estimation of tacrolimus area under the concentration-time curve (AUC0-12). Tacrolimus concentration was measured by liquid chromatography tandem mass spectrometry and acetaminophen absorption method was used to characterize gastric emptying time.Demographic and biochemical characteristics were comparable between the two groups with the exception of significantly higher glycated hemoglobin levels in patients with diabetes (P = 0.02). Time to maximum concentration (Tmax) of acetaminophen was significantly longer in diabetics [D: 74.1 minute versus nondiabetics (ND): 29.3 minutes, P = 0.02]; however, tacrolimus Tmax was not significantly different (D: 121 minutes versus ND: 87 minutes, P = 0.15). Median (interquartile range) of tacrolimus AUC0-12 was 114 (101-161) μg*hr/L in patients with diabetes and 113 (87-189) μg*hr/L in nondiabetics (P = 0.62). The following limited sampling equation [AUCpred (μg*hr/L) = 18.70 - 1.72 C1hr - 4.09 C2hr + 14.40 C3hr] was derived from a training data set that included 10 patients. The correlation coefficient between model-predicted and observed AUC0-12 values was 0.999. Mean prediction error and root mean square error of the model-predicted values derived from the patients in validation data set were 0.04 and 17.48 μg*hr/L, respectively.In conclusion, it appears that diabetes has a modest effect on the rate but not the extent of tacrolimus absorption, and a three-point abbreviated sampling strategy common to both groups may prove useful for the estimation of tacrolimus exposure in kidney transplant recipients. © 2007 Lippincott Williams & Wilkins, Inc

Pharmacokinetics of total and unbound prednisone and prednisolone in stable kidney transplant recipients with diabetes mellitus

Background: The corticosteroid prednisone is an important component of posttransplantation immunosuppressive therapy. Pharmacokinetic parameters of prednisone or its pharmacologically active metabolite, prednisolone, are not well characterized in transplant recipients. The objective of this study was to compare the pharmacokinetics of total and unbound prednisone and prednisolone in diabetic and nondiabetic stable kidney transplant recipients and to evaluate the factors influencing plasma protein binding of prednisolone. Methods: Prednisone and prednisolone concentration-time profiles were obtained in 20 diabetic and 18 nondiabetic stable kidney transplant recipients receiving an oral dose of 5-10 mg prednisone per day. In addition to drug and metabolite exposures, factors influencing prednisolone protein binding were evaluated using a nonlinear mixed-effects modeling approach. This model takes into account the binding of prednisolone and cortisol to corticosteroid-binding globulin (CBG) in a saturable fashion and binding of prednisolone to albumin in a nonsaturable fashion. Finally, we have investigated the influence of several covariates including diabetes, glucose concentration, hemoglobin A1c, creatinine clearance, body mass index, gender, age, and time after transplantation on the affinity constant (K) between corticosteroids and their binding proteins. Results: In patients with diabetes, the values of dose-normalized area under the concentration-time curves were 27% and 23% higher for total and unbound prednisolone, respectively. Moreover, the ratio of total prednisolone to prednisone concentrations (active/inactive forms) was higher in diabetic subjects (P \u3c 0.001). Modeling protein binding results revealed that the affinity constant of corticosteroid-binding globulin-prednisolone (KCBG,PL) was related to the patient\u27s gender and diabetes status. Conclusions: Higher prednisolone exposure could potentially lead to the increased risk of corticosteroid-related complications in diabetic kidney transplant recipients. Copyright © 2014 by Lippincott Williams & Wilkins

Pharmacokinetics of Total and Unbound Prednisone and Prednisolone in Stable Kidney Transplant Recipients With Diabetes Mellitus

Base, showing how the buildings meets the ground; The building was designed by Lord Foster, his then business partner Ken Shuttleworth, and Arup engineers, and was constructed by Skanska of Sweden in 2001–2004. The Swiss Re Headquarters at 30 St Mary Axe,popularly known as the Gherkin, won the Stirling Prize for 2004. 30 St Mary Axe is London's first environmental skyscraper, located in the heart of the City of London. A comprehensive range of sustainable measures mean that the building will use 50% less energy than a traditional prestige office building. Fresh air is drawn up through the spiralling light-wells to naturally ventilate the office interiors and minimise reliance on artificial cooling and heating. The light-wells and the shape of the building maximise natural daylight, moderate the use of artificial lighting and allow views out from deep within the building. The exterior cladding consists of 5,500 flat triangular and diamond shaped glass panels, which vary at each level. The glazing to the office areas consists of a double-glazed outer layer and a single-glazed inner screen that sandwich a central ventilated cavity which contains solar-control blinds. The building is currently the 6th tallest in London. Source: Foster + Partners [website]; http://www.fosterandpartners.com/ (accessed 6/15/2009

Concentrations of mycophenolic acid and glucuronide metabolites under concomitant therapy with cyclosporine or tacrolimus

Mycophenolate mofetil [MMF, the prodrug of mycophenolic acid (MPA)] is usually administered at double doses with cyclosporine than with tacrolimus because it is believed that MPA exposure is lower during cyclosporine therapy. This study aimed to compare 12 hour, steady-state concentration-time profiles of MPA and its phenol- and acyl-glucuronide metabolites (MPAG and AcMPAG, respectively) in stable kidney transplant recipients maintained either on cyclosporine (n = 12) or tacrolimus (n = 12). During the absorption phase in the cyclosporine group, dose-normalized concentrations of total and free MPA were significantly higher but the overall area under the concentration-time curve (AUC0-12) was not significantly different. Additionally, exposure to AcMPAG was higher in the cyclosporine group (P \u3c 0.05). Ten of 12 patients in the cyclosporine group were on ketoconazole therapy; however, the exposure to MPA or MPAG was not different when MMF was given orally to Sprague-Dawley rats with or without ketoconazole. In conclusion, cyclosporine modulates the disposition of MPA and metabolites differently from tacrolimus; however, patients on cyclosporine may not require double doses of MMF to achieve the same exposure. © 2007 Lippincott Williams & Wilkins, Inc

Multidrug resistance-associated protein 2 (MRP2/ABCC2) haplotypes significantly affect the pharmacokinetics of tacrolimus in kidney transplant recipients

Background and Objective: Tacrolimus is an immunosuppressive drug used for the prevention of the allograft rejection in kidney transplant recipients. It exhibits a narrow therapeutic index and large pharmacokinetic variability. Tacrolimus is mainly metabolized by cytochrome P450 (CYP) 3A4 and 3A5 and effluxed via ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp), encoded by ABCB1 gene. The influence of CYP3A53 on the pharmacokinetics of tacrolimus has been well characterized. On the other hand, the contribution of polymorphisms in other genes is controversial. In addition, the involvement of other efflux transporters than P-gp in tacrolimus disposition is uncertain. The present study was designed to investigate the effects of genetic polymorphisms of CYP3As and efflux transporters on the pharmacokinetics of tacrolimus. Subjects and Methods: A total of 500 blood concentrations of tacrolimus from 102 adult stable kidney transplant recipients were included in the analyses. Genetic polymorphisms in CYP3A4 and CYP3A5 genes were determined. In addition, the genes of efflux transporters including P-gp (ABCB1), multidrug resistance-associated protein (MRP2/ABCC2) and breast cancer resistance protein (BCRP/ABCG2) were genotyped. For ABCC2 gene, haplotypes were determined as follows: H1 (wild type), H2 (1249G\u3eA), H9 (3972C\u3eT) and H12 (-24C\u3eT and 3972C\u3eT). Population pharmacokinetic analysis was performed using nonlinear mixed effects modeling. Results: Analyses revealed that the CYP3A5 expressers (CYP3A51 carriers) and MRP2 high-activity group (ABCC2 H2/H2 and H1/H2) showed a decreased dose-normalized trough concentration of tacrolimus by 2.3-fold (p \u3c 0.001) and 1.5-fold (p = 0.007), respectively. The pharmacokinetics of tacrolimus were best described using a two-compartment model with first order absorption and an absorption lag time. In the population pharmacokinetic analysis, CYP3A5 expressers and MRP2 high-activity groups were identified as the significant covariates for tacrolimus apparent clearance expressed as 20.7 × (age/50)-0.78 × 2.03 (CYP3A5 expressers) × 1.40 (MRP2 high-activity group). No other CYP3A4, ABCB1 or ABCG2 polymorphisms were associated with the apparent clearance of tacrolimus. Conclusions: This is the first report showing that MRP2/ABCC2 has a crucial impact on the pharmacokinetics of tacrolimus in a haplotype-specific manner. Determination of the ABCC2 as well as CYP3A5 genotype may be useful for more accurate tacrolimus dosage adjustment. © 2013 Springer International Publishing Switzerland