A Low Tacrolimus Concentration-to-Dose Ratio Increases Calcineurin Inhibitor Nephrotoxicity and Cytomegalovirus Infection Risks in Kidney Transplant Recipients: A Single-Center Study in Japan

BACKGROUND

Tacrolimus (TAC) has several problems due to its narrow therapeutic window and variations pharmacokinetics and pharmacodynamics. Recently, several studies reported that TAC metabolism, defined by TAC blood trough concentration to dose (C/D) ratio, was associated with TAC toxicity. Reports on once-daily extended-release TAC (TAC-ER) are limited. The present study aimed to investigate the effect of the TAC metabolic rate on TAC-ER and compare TAC area under the curve (AUC) between fast and slow metabolizers.

METHODS

A total of 58 recipients were included in this study. The optimal cut-off value and time of the C/D ratio on TAC-ER for fast and slow metabolizers was determined using receiver operating characteristic curve analysis for biopsy-proven calcineurin inhibitor (CNI) nephrotoxicity.

RESULTS

The optimal time to evaluate the C/D ratio was 1 month after kidney transplantation (KT) and the cut-off value was 0.9. The multivariate analysis for CNI nephrotoxicity risk showed that only TAC metabolism was associated with CNI nephrotoxicity (hazard ratio 10.60, P = .005, 95% CI 2.03-55.22). Cytomegalovirus infection occurred more frequently in fast metabolizers when the cut-off value of the C/D ratio was set to 0.9 at 3 months after KT (P = .04). The TAC C₄, AUC_2-8, was higher in fast metabolizers than in slow metabolizers (P < .01, P = .03, respectively).

CONCLUSION

The study revealed that TAC fast metabolizers on TAC-ER may be classified as a high-risk group for CNI nephrotoxicity and cytomegalovirus infection. The result of TAC AUC supported the hypothesis that fast metabolizers tended to be overexposed to immunosuppressive agents early after oral administration.

Hospital Pharmacometrics for Optimal Individual Administration of Antimicrobial Agents for Anti-methicillin-resistant Staphylococcus aureus Infected Patients

Therapeutic drug monitoring and target concentration intervention based on population pharmacokinetic and pharmacodynamic models has been strongly recommended for anti-methicillin-resistant Staphylococcus aureus (MRSA) agents in order to provide appropriate antimicrobial chemotherapy to each individual patient, and pharmacokinetic and pharmacodynamic analyses in hospitalized patients have been actively conducted, as evidenced with vancomycin. Teicoplanin, daptomycin, and linezolid have been the most studied antibiotics, using population pharmacokinetics of patients with MRSA. Infections caused by MRSA have higher severity and fatality rates than other antimicrobial-susceptible infections. Therefore, many medical facilities have been implementing infection control programs based on antimicrobial stewardship to prevent nosocomial infections and drug-resistant strains. Studies detailing pharmacometrics for these antibiotics have been reported to elucidate the pharmacokinetic and pharmacodynamic properties, to determine significant factors influencing variabilities between individuals, and to develop target concentration interventions and dosing regimens for adults, the elderly, patients with renal insufficiency including those on continuous renal replacement therapies, patients with low body weight, obese patients, and pediatric patients. This review presents the details of our recent research on the optimal dosing design of antimicrobial agents for the treatment of MRSA infection based on hospital pharmacometrics. In addition, the prospect of using modeling and simulation has shown major advantages in supporting dosing regimen selection.

Optimal blood levels of (extended-release) tacrolimus in living donor kidney transplantation to prevent de novo donor-specific antibody production: A retrospective cohort study

Chronic antibody-mediated rejection, caused by de novo donor-specific antibody (dnDSA) production, results in poor graft survival. To prevent dnDSA production, optimal blood levels of immunosuppressive drugs in living donor kidney transplant recipients were determined. A total of 772 recipients underwent living donor kidney transplantation between January 2008 and December 2017. Graft survival and risk factors for dnDSA production were investigated in 647 recipients. Optimal blood levels of tacrolimus (TAC) and extended-release TAC (TACER) were measured in recipients receiving steroids and mycophenolate mofetil, combined with TAC (n = 53) or TACER (n = 135). Receiver operating characteristic (ROC) curve analysis and comparisons between dnDSA-negative and dnDSA-positive recipients were carried out. The Kaplan-Meier method revealed significantly poor graft survival in dnDSA-positive recipients (P < 0.001). Cox regression models indicated calcineurin inhibitor withdrawal as a significant risk for dnDSA production (P < 0.001; hazard ratio 6.637; 95% confidence interval 2.667-6.517). Average trough levels of TAC and TACER in dnDSA-negative recipients were significantly higher than those in dnDSA-positive recipients (4.88 vs 3.69 ng TAC/ml, P = 0.023, and 4.60 vs 3.85 ng TACER/ml, P = 0.001). ROC curve analysis indicated 4.325 and 3.990 ng/ml as the best trough levels under TAC- and TACER-based regimens, respectively, to prevent dnDSA production (areas under the curve: 0.788 and 0.813, respectively). Maintenance of the trough levels of TAC > 4.325 ng/ml and TACER > 3.990 ng/ml may prevent dnDSA production.

The Effect of Maintenance Treatment with Twice-Daily or Prolonged Once-Daily Tacrolimus Formulation on Visual Evoked Potentials in Stable Kidney Transplant Recipients

In kidney transplant recipients (KTRs), uraemia-induced central nervous system damage partly subsides, while the long-lasting exposure to tacrolimus may cause pathologic visual evoked potentials (VEP) findings, which have not been investigated yet. Thus, the aim of the present study was to assess the effect of tacrolimus maintenance treatment on bioelectrical function of optic nerves in stable KTRs. Sixty-five stable KTRs were enrolled, including 30 patients treated with twice-daily (Prograf) and 35 patients treated with prolonged once-daily (Advagraf) tacrolimus formulation. In all patients, pattern and flash VEP measurements were performed. Tacrolimus dosing and exposure were also analyzed. Overall, 129 eyes were analyzed. In pattern VEP, both (1°) and (15') latencies of P100 waves were significantly longer, whereas (1°) and (15') amplitudes were lower in the Advagraf group as compared with the Prograf group. Multivariate regression analyses revealed that the use of Advagraf (vs. Prograf) was independently associated with longer (1°) and (15') P100 latencies and lower corresponding amplitudes, whereas log tacrolimus daily dose was only related to amplitudes in a whole study group. In flash VEP, log tacrolimus trough level was associated with negative changes in P2 wave amplitude irrespective of tacrolimus formulation, whereas its association with P2 latency was observed only in the Prograf group. Both the type of tacrolimus formulation and drug exposure influenced the VEP parameters in stable KTRs.

Association of the clinical efficacy of vancomycin with the novel pharmacokinetic parameter area under the trough level (AUTL) in elderly patients with hospital-acquired pneumonia

WHAT IS KNOWN AND OBJECTIVE

The pharmacokinetic-pharmacodynamic parameter that best predicts the efficacy of vancomycin is the ratio of the area under the concentration versus time curve (AUC) to the minimum inhibitory concentration (MIC). A 24-h AUC (AUC24 )/MIC ratio ≥ 400 was recommended in an American consensus review, but vancomycin treatment occasionally fails despite maintenance of AUC24 /MIC ≥ 400. We evaluated the association between clinical efficacy of vancomycin and two novel pharmacokinetic parameters, the 'area under the trough level' (AUTL) and the 'area above the trough level' (AATL), in hospitalized elderly patients with methicillin-resistant Staphylococcus aureus (MRSA) pneumonia.

METHODS

The subjects were hospitalized elderly patients who were administered vancomycin for treatment of MRSA pneumonia between 2006 and 2012 at Sasebo Chuo Hospital (Nagasaki, Japan). Pharmacokinetic parameters of vancomycin were estimated for each patient by Bayesian analysis using population pharmacokinetic parameters for Japanese patients. Based on the patient-specific parameters thus obtained, AUC24 values were calculated as the vancomycin dosage divided by vancomycin clearance. AUTL was calculated as the trough serum concentration multiplied by 24 h, whereas AATL was calculated by subtracting AUTL from AUC24 .

RESULTS AND DISCUSSION

Logistic regression analysis demonstrated that efficacy of vancomycin was more strongly associated with AUTL than AUC24 . The optimal cut-off value of AUTL was 331 μg∙h/mL, which means that the optimal cut-off value of the trough serum concentration was 13·8 μg/mL.

WHAT IS NEW AND CONCLUSION

Efficacy of vancomycin was associated with AUTL, a novel pharmacokinetic parameter. Determining the target AUTL or trough concentration may enhance the efficacy of vancomycin therapy in elderly patients with MRSA pneumonia. Given that nephrotoxicity may increase with a Ctrough in excess of 15 μg/mL, this level should ideally not be exceeded.

No acceleration of UV-induced skin carcinogenesis from evenly spread dietary intake of cyclosporine in contrast to oral bolus dosages

BACKGROUND

Organ transplant recipients using the immunosuppressant cyclosporine have an increased risk for developing nonmelanoma skin cancer. Disparate effects of cyclosporine have, however, been reported on UV-induced skin carcinogenesis in mouse experiments. Therefore, we set out to compare three experimental protocols using mice, with the aim to emulate most closely the increased skin cancer risk in organ transplant recipients.

METHODS

UV carcinogenesis was performed in hairless SKH-1 mice by three protocols: dietary cyclosporine and daily UV exposures, dietary cyclosporine after a period of UV exposures, and bolus dosing cyclosporine by gavage and repeated UV exposures.

RESULTS

Using chronic UV exposure, continuous dietary administration of cyclosporine was shown to inhibit tumor formation. Dietary cyclosporine after a period of UV exposures did not affect ensuing UV carcinogenesis. However, in contrast with dietary cyclosporine, bolus dosages of cyclosporine by gavage, resulting in strongly varying blood levels of cyclosporine, increased tumor development in chronically UV-exposed mice. There was no difference in tumor development between mice UV-irradiated during peak or trough levels of cyclosporine in the blood. Time-averaged levels in these mice were similar to those with cyclosporine in the diet.

CONCLUSIONS

Cyclosporine in bolus doses appears to increase skin cancer development, whereas cyclosporine administration more evenly spread over time does not. Extrapolation to transplant patients suggests that the mode of administrating cyclosporine may be crucial for the increased skin cancer risk and that this risk might be lowered with a more steady release of cyclosporine in the body.

Pharmacokinetics of Cyclosporine A in Chinese heart transplant recipients

AIM

To determine the steady state concentration and the pharmacokinetics of Cyclosporine A (CsA) in heart transplant recipients.

METHODS

A single dose of 100 mg CsA capsules twice daily was given to five heart transplant recipients of steady state. The concentrations of CsA in plasma were determined by streptavidin peroxidase fluorescent polarization immunoassay.

RESULTS

The main pharmacokinetic parameters of CsA were as follows: t(max) (1.60 ± 0.55) h, ρmax(951.60 ± 229.20) μg.L-1, t1/2(6.53 ± 2.40) h, and AUC0 -t(5162.10 ± 1355.01) μg.h.L-1.

CONCLUSION

The study obtained the steady state pharmacokinetic parameters of CsA in Chinese heart transplant recipients.

Pharmacokinetics of orally administered tacrolimus in lupus nephritis patients

The pharmacokinetics of orally administered tacrolimus were examined in six female lupus nephritis patients (mean age 43 years, range 24-55 years). Tacrolimus (3 mg) was administered after supper, and blood tacrolimus concentrations were measured just prior to dosing and 1, 2, 4, 6, 8, 12 and 24 h after administration. The maximum blood concentration (C(max)) was observed 4-8 h (mean: 6.7 h) after administration. The mean C(max) and area under the tacrolimus concentrationti-me curve (AUC(0-24 h)) were 12.7 ng/ml and 163.1 ng x h/ml, respectively. Although there was a weak correlation between AUC(0-24 h) values and tacrolimus concentrations 2, 4, and 6 h after administration, concentrations at 12 h and 24 h were highly correlated with AUC(0-24 h) values, suggesting that the trough concentration (C(24 h)) and C(12 h) are valid markers for therapeutic tacrolimus monitoring. Enzyme-linked immunoabsorbent assay (ELISA) and microparticle enzyme immunoassay (MEIA) measurements of blood tacrolimus concentrations were similar. We recommend that monitoring should be carried out by C(12 h) in lupus nephritis outpatients.