Model-Informed Dosing Optimization of Tacrolimus for Concomitant Administration with Itraconazole to Japanese Lung Transplant Recipients.

BACKGROUND: Tacrolimus is an immunosuppressant administered to patients undergoing lung transplantation. Itraconazole is often concomitantly used with tacrolimus to prevent fungal infections and increase tacrolimus concentration. However, the pharmacokinetics of tacrolimus in Japanese lung transplant recipients and the effect of itraconazole on its pharmacokinetics have not been adequately evaluated. Population pharmacokinetic analysis was conducted to develop an optimal dose adjustment method for use upon itraconazole initiation in Japanese lung transplant recipients. METHODS: This study comprised Japanese lung transplant recipients whose blood tacrolimus and itraconazole concentrations were measured between January 2017 and December 2019. A nonlinear mixed-effects modeling program was used to explore the covariates of tacrolimus pharmacokinetics and effects of concomitant itraconazole use. Using the model, the optimal initial tacrolimus dose was calculated and a dose adjustment method comprising concomitant itraconazole use was developed. RESULTS: A total of 1693 tacrolimus trough blood concentrations and 85 itraconazole trough plasma concentrations were obtained from 43 patients. Postoperative day, albumin level, and administration route were extracted as covariates for tacrolimus pharmacokinetics. The drug-drug interaction between tacrolimus and itraconazole could be predicted more accurately by considering the concentration-dependent inhibition of itraconazole. The optimal initial tacrolimus dose was 2.0 mg twice daily for tube and 1.5 mg twice daily for oral administration. To maintain the target concentration, the tacrolimus dose was reduced by 60% upon itraconazole initiation. CONCLUSIONS: This study is the first to use population pharmacokinetic analysis to assess the interaction between tacrolimus and itraconazole in patients who underwent lung transplantation. These results provide useful insights for optimizing the initial tacrolimus dose for concomitant itraconazole use.

Trough ganciclovir concentration as predictor of leukopenia in lung transplant recipients receiving valganciclovir prophylaxis.

BACKGROUND: Valganciclovir is the first-line agent for Cytomegalovirus prophylaxis after lung transplantation. However, its use is associated with a relatively high risk of hematological toxicity. This study aimed to investigate the relationship between trough ganciclovir concentration and hematologic toxicity in lung transplantation patients receiving valganciclovir prophylaxis, and identify factors that affect ganciclovir pharmacokinetics in this population. METHODS: This prospective observational study included 24 lung transplant patients receiving valganciclovir prophylaxis. The cutoff value of trough ganciclovir concentration was estimated using receiver operating characteristic analysis in leukopenia grade 3 and higher. Population pharmacokinetic analysis was performed using a nonlinear mixed-effects modeling program. RESULTS: The trough ganciclovir concentration was significantly higher in the group with leukopenia grades 3 or higher than in the group with grades less than or equal to 2 (1605.7 ± 860.1 ng/mL [n = 3] vs. 380.5 ± 175.8 ng/mL (n = 21), p < .001). The cutoff value of trough ganciclovir concentration for predicting greater than or equal to grade 3 leukopenia was estimated as 872.0 ng/mL. Creatinine clearance and lung re-transplantation were found to have a significant impact on the total body clearance of valganciclovir. Ganciclovir clearance was decreased in patients with reduced creatine clearance or re-transplantation. CONCLUSION: These results suggest that higher ganciclovir trough concentrations are associated with an increased risk of leukopenia grade 3 or higher, and that creatinine clearance and lung re-transplantation affected the pharmacokinetics of ganciclovir.

In Vitro Evidence of Potential Interactions between CYP2C8 and Candesartan Acyl-ß-D-glucuronide in the Liver.

Growing evidence suggests that certain glucuronides function as potent inhibitors of CYP2C8. We previously reported the possibility of drug-drug interactions between candesartan cilexetil and paclitaxel. In this study, we evaluated the effects of candesartan N2-glucuronide and candesartan acyl-ß-D-glucuronide on pathways associated with the elimination of paclitaxel, including those involving organic anion-transporting polypeptide (OATP) 1B1, OATP1B3, CYP2C8, and CYP3A4. UDP-glucuronosyltransferase (UGT) 1A10 and UGT2B7 were found to increase candesartan N2-glucuronide and candesartan acyl-ß-D-glucuronide formation in a candesartan concentration-dependent manner. Additionally, the uptake of candesartan N2-glucuronide and candesartan acyl-ß-D-glucuronide by cells stably expressing OATPs is a saturable process with K m of 5.11 and 12.1 µM for OATP1B1 and 28.8 and 15.7 µM for OATP1B3, respectively; both glucuronides exhibit moderate inhibition of OATP1B1/1B3. Moreover, the hydroxylation of paclitaxel was evaluated using recombinant CYP3A4 and CYP3A5. Results show that candesartan, candesartan N2-glucuronide, and candesartan acyl-ß-D-glucuronide inhibit the CYP2C8-mediated metabolism of paclitaxel, with candesartan acyl-ß-D-glucuronide exhibiting the strongest inhibition (IC50 is 18.9 µM for candesartan acyl-ß-D-glucuronide, 150 µM for candesartan, and 166 µM for candesartan N2-glucuronide). However, time-dependent inhibition of CYP2C8 by candesartan acyl-ß-D-glucuronide was not observed. Conversely, the IC50 values of all the compounds are comparable for CYP3A4. Taken together, these data suggest that candesartan acyl-ß-D-glucuronide is actively transported by OATPs into hepatocytes, and drug-drug interactions may occur with coadministration of candesartan and CYP2C8 substrates, including paclitaxel, as a result of the inhibition of CYP2C8 function. SIGNIFICANCE STATEMENT: This study demonstrates that the acyl glucuronidation of candesartan to form candesartan acyl-ß-D-glucuronide enhances CYP2C8 inhibition while exerting minimal effects on CYP3A4, organic anion-transporting polypeptide (OATP) 1B1, and OATP1B3. Thus, candesartan acyl-ß-D-glucuronide might represent a potential mediator of drug-drug interactions between candesartan and CYP2C8 substrates, such as paclitaxel, in clinical settings. This work adds to the growing knowledge regarding the inhibitory effects of glucuronides on CYP2C8.

Neutrophil Gelatinase-Associated Lipocalin Is Not Associated with Tacrolimus-Induced Acute Kidney Injury in Liver Transplant Patients Who Received Mycophenolate Mofetil with Delayed Introduction of Tacrolimus.

Tacrolimus is widely used as an immunosuppressant in liver transplantation, and tacrolimus-induced acute kidney injury (AKI) is a serious complication. The urinary neutrophil gelatinase-associated lipocalin (NGAL) level has been linked to tacrolimus-induced AKI in patients starting tacrolimus treatment the morning after liver transplantation. Here we tested this association using a different immunosuppression protocol: Mycophenolate mofetil administration beginning on Postoperative Day 1 and tacrolimus administration beginning on Postoperative Day 2 or 3. Urine samples were collected from 26 living donor liver transplant recipients before (Postoperative Day 1) and after (Postoperative Day 7 or 14) tacrolimus administration. NGAL levels were measured via enzyme-linked immunosorbent assays, as were those of three additional urinary biomarkers for kidney diseases: Monocyte chemotactic protein-1 (MCP-1), liver-type fatty acid-binding protein (L-FABP), and human epididymis secretory protein 4 (HE4). HE4 levels after tacrolimus administration were significantly higher in patients who developed AKI (n = 6) than in those who did not (n = 20), whereas NGAL, MCP-1, and L-FABP levels did not differ significantly before or after tacrolimus administration. These findings indicate that NGAL may not be a universal biomarker of AKI in tacrolimus-treated liver transplant recipients. To reduce the likelihood of tacrolimus-induced AKI, our immunosuppression protocol is recommended.

Concomitant administration of candesartan cilexetil in patients on paclitaxel and carboplatin combination therapy increases risk of severe neutropenia
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OBJECTIVE: Angiotensin receptor blockers (ARBs) are often used in patients on paclitaxel (PTX) and carboplatin combination (TC) therapy to treat hypertension caused by the co-administration of bevacizumab. The aim of this retrospective study was to analyze the association between co-administration of ARBs and the development of severe neutropenia in patients on TC therapy. MATERIALS AND METHODS: In this study, 211 concomitant medications were prescribed to 173 patients on TC therapy. 24 of those patients received ARBs. The incidences of neutropenia among those on various ARBs were compared. RESULTS: Patients on candesartan cilexetil had the highest incidence of neutropenia compared to those on other concomitant medications, including other ARBs. Of 173 patients, 6 received candesartan cilexetil during the first cycle of TC therapy, and all 6 of them developed severe neutropenia. We noted that prior to TC therapy, there were no significant differences in age, serum albumin levels, neutrophil counts, liver injury marker, and renal function between the patients on candesartan cilexetil and those on other ARBs. CONCLUSION: Our data suggest that a drug-drug interaction between candesartan cilexetil and TC therapy is probable. Unlike with other ARBs, the possible increased risk for development of severe neutropenia should be taken into account when prescribing candesartan cilexetil in combination with TC therapy.
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Previous Dosage of Allopurinol Is a Strong Determinant of Febuxostat Efficacy.

Febuxostat has currently played pivotal role in the treatment of hyperuricemia, but there is little comprehensive information for the determinants of individual difference in efficacy of febuxostat. Therefore, the present study, a retrospective investigation, was carried out to analyze the effects of patient characteristics on the efficacy of febuxostat. A total of 225 patients who were continuously prescribed the same dose of febuxostat for 8-12 weeks from the initial therapy were enrolled in the present study. The data, including patient information and laboratory data, were collected from electronic medical records. Serum urate lowering effects of febuxostat were evaluated by calculating the change in serum urate level at baseline and at 8-12 weeks after starting febuxostat. The multiple regression analysis showed the change in serum urate level was significantly lower in male patients and in those with a lower baseline serum urate level, higher previous dose of allopurinol, lower dose of febuxostat and lower body surface area-unadjusted estimated glomerular filtration rate. Concomitantly administered drugs did not show a significantly influence on the efficacy of febuxostat. In conclusion, it should be noted that the serum urate lowering efficacy of febuxostat may decrease in patients with a higher previous dose of allopurinol, renal impairment or male patients. The basic findings of the present study are believed to contribute to the proper use of febuxostat.

A case of successful contribution of therapeutic drug monitoring of valganciclovir as the prophylaxis against cytomegalovirus infection in a lung transplant recipient.

BACKGROUND: Ganciclovir and its prodrug, valganciclovir, are first-line agents for cytomegalovirus infection prophylaxis after lung transplantation. Although valganciclovir prophylaxis is known to result in severe leukopenia as an adverse effect, dosage adjustment based on therapeutic drug monitoring (TDM) of ganciclovir concentration is not generally implemented in clinical practice. CASE PRESENTATION: In this report, we describe the case of a female in her fifties after lung transplantation who successfully maintained valganciclovir prophylaxis under TDM with a minimal occurrence of severe leukopenia. Valganciclovir administration was initiated at a conventional dose of 450 mg/day on postoperative day 43 but was reduced to 450 mg/2 days on postoperative day 69 because of a decrease in white blood cell count and an increase in trough ganciclovir concentration. Subsequently, the valganciclovir dose adjustment was switched from label-indicated renal function-guided dosing to TDM-based dosing, targeting a trough level of 300-800 ng/mL. This target range was determined through deliberations with infectious disease specialists and pharmacists based on previously reported data. The TDM-based dose adjustment successfully prevented cytomegalovirus reactivation without causing significant adverse effects. Valganciclovir prophylaxis was completed on postoperative day 256, and the patient was transferred to another hospital for rehabilitation. CONCLUSIONS: The findings of the present case suggest that TDM-based dosing could be helpful for clinicians in optimizing the prophylactic administration of valganciclovir in patients undergoing lung transplantation.

Association between Proton Pump Inhibitors, Immune Checkpoint Inhibitors, and Acute Kidney Injury: A Nested Case-Control Study.

BACKGROUND: An association between proton pump inhibitor (PPI) use and an increased risk of acute kidney injury (AKI) has been confirmed. This study aimed to evaluate the effects of PPI use on the risk of AKI in patients with cancer who were administered immune checkpoint inhibitors (ICIs), a class of drugs used in cancer treatment, and in those who were not. METHODS: We used a database provided by the Health, Clinic, and Education Information Evaluation Institute, which included demographic data, diagnoses, prescriptions, and laboratory results. We conducted a nested case-control study of 38,930 patients with cancer who were new PPI or ICI users and had no history of AKI before cohort entry. The odds ratio (OR) for AKI was estimated using conditional logistic regression models. RESULTS: During a mean follow-up of 8.3 months, 5,870 cases of AKI were identified (incidence rate, 21.9/100 person-years). Compared to never or past PPI use without ICI use, the adjusted ORs of AKI for current PPI use without ICI use, past or never PPI use with prior ICI use, current PPI use with prior ICI use were 1.82 (95% CI, 1.67 to 2.00), 1.47 (95% CI, 1.17 to 1.86), or 2.13 (95% CI, 1.42 to 3.20), respectively. The risk of AKI in patients treated with both PPIs and ICIs was not higher than the additional or multiplication of the risks in those who were treated with PPIs or ICIs alone. CONCLUSIONS: This study reinforces the association between PPIs and ICIs use and the increased risk of AKI. Although the interaction between the two drug classes was not detected, these findings highlight the need for careful monitoring and evaluation of kidney function in patients treated with PPIs and ICIs.

Influence of ensitrelvir or nirmatrelvir/ritonavir on tacrolimus clearance in kidney transplant recipients: a single-center case series.

BACKGROUND: Among the oral antivirals used for treating patients with mild-to-moderate novel coronavirus disease 2019 (COVID-19), nirmatrelvir/ritonavir (NMV/RTV) and ensitrelvir (ESV) are inhibitors of cytochrome P450 (CYP) 3A, and therefore, can cause drug-drug interactions with concomitant medications. Tacrolimus (TAC), a substrate of CYP3A4/5, is administered for a long period to prevent rejection after kidney transplantation. TAC should be discontinued while using NMV/RTV because blood TAC levels significantly increase when these drugs are concomitantly administered. However, the influence of ESV on blood TAC levels has not yet been reported, and the management of TAC doses during the use of ESV remains unclear. CASE PRESENTATION: We experienced three kidney transplant recipients with COVID-19, whose blood trough levels of TAC increased by the concomitant use of NMV/RTV or ESV. In two patients administering NMV/RTV, blood trough levels of TAC increased more than tenfold after combination therapy, whereas in one patient administering ESV, TAC level increased approximately threefold. CONCLUSIONS: These cases suggest that TAC administration should be discontinued during NMV/RTV treatment to maintain blood TAC levels within the therapeutic range, and a reduced TAC dose is sufficient during ESV treatment.

Potential treatment option of rivaroxaban for breastfeeding women: A case series.

The use of direct oral anticoagulants (DOACs) in breastfeeding women is currently challenging due to limited safety data for breastfeeding infants, and there have been no previous studies on the drug concentration in breastfeeding infants. We treated 2 patients (one case was twin pregnancy) with venous thromboembolisms in breastfeeding women administered rivaroxaban at our institution. Blood samples from the mothers and breastmilk samples were collected at time 0 and 2 h after the rivaroxaban administration, breastfeeding was conducted 2 h after the rivaroxaban administration, and blood samples from the infants were collected 2 h after breastfeeding (4 h after maternal rivaroxaban administration). The milk-to-plasma (M:P) ratios were 0.27 in Case 1 and 0.32 in Case 2. The estimated relative infant dose (RID) was 0.82 % in Case 1 Children 1 and 2, and 1.27 % in Case 2. The rivaroxaban concentration in the infant plasma was below the lower limit of quantification in all infants. In addition, even in the high-exposure case simulation based on 5 days of breastfeeding in Case 2, the infant plasma concentration level was below the lower limit of quantification. At 3 months of follow-up, breastfeeding was continued, and all infants grew and developed without any health problems including bleeding events. The current case series showed that there were no pharmacokinetic or clinical concerns for breastfeeding women or breastfed infants, and provides support for rivaroxaban as a safe treatment option for these patients.

Acceleration of carboxylesterase-mediated activation of irinotecan to SN-38 by serum from patients with end-stage kidney disease.

PURPOSE: Pharmacokinetics and pharmacodynamics of irinotecan have been reported to be altered in cancer patients with end-stage kidney disease (ESKD). Carboxylesterase (CES) has an important role in metabolism of irinotecan to its active metabolite, SN-38, in human liver. The purpose of the present study was to investigate whether CES activity was altered in ESKD patients. METHODS: The present study investigated the effects of uremic serum, uremic toxins, and fatty acids on the hydrolysis of irinotecan and a typical CES substrate, p-nitrophenyl acetate (PNPA), in human liver microsomes. Normal and uremic serum samples were deproteinized by treatment with methanol were used in the present study. RESULTS: The present study showed that both normal and uremic serum significantly inhibited CES-mediated metabolism of both irinotecan and PNPA. The inhibition by uremic serum was weaker than that by normal serum, suggesting that CES activity may be higher in ESKD patients. Although four uremic toxins did not affect PNPA metabolism, arachidonic acid inhibited it. There was no difference in inhibitory effect of PNPA metabolism between both mixtures of seven fatty acids used at concentrations equivalent to those present in 10% normal or uremic serum. Interestingly, those mixtures had a more pronounced effect than either 10% normal or uremic serum. CONCLUSIONS: The present study showed that the inhibition of CES activity by uremic serum was weaker than that by normal serum, suggesting that an increase in maximum plasma concentration of SN-38 in cancer patients with ESKD can be attributed to an accelerated CES-mediated irinotecan hydrolysis.

Cooperative inhibitory effects of uremic toxins and other serum components on OATP1B1-mediated transport of SN-38.

PURPOSE: Half-life of SN-38, an active metabolite of irinotecan, remarkably increases in patients with end-stage kidney disease (ESKD), even though SN-38 is excreted in bile. Uremic toxins (UTs), which accumulate in the serum of ESKD patients, were reported to inhibit organic anion-transporting polypeptide (OATP) 1B1-mediated uptake of SN-38; however, the relevance of this finding in a clinical setting is unknown. This study focused on cooperative effects of serum components and UTs on OATP1B1-mediated transport of SN-38. METHODS: Uptake of SN-38 by OATP1B1 was evaluated using cells stably expressing OATP1B1. Serum was obtained from > 400 ESKD patients undergoing hemodialysis. Deproteinized serum was combined with human serum albumin (HSA) to explore the effects of albumin-bound and unbound serum compounds. RESULTS: Uptake clearance of SN-38 in OATP1B1 cells decreased by 40% in the presence of uremic serum residue with albumin compared to that in the presence of normal serum residue. Additional UTs (3-carboxy-4-methyl-5-propyl-2-furanpropionic acid, hippuric acid, indole-3-acetic acid, and 3-indoxyl sulfate) combined with normal serum residue in HSA decreased OATP1B1-mediated SN-38 transport by 32.1% compared to that in the presence of normal serum residue. The inhibitory effect of albumin-unbound fraction with UTs and normal serum residue was comparable to that of uremic serum residue, with an uptake decrease of 17.2% compared to that reported in the presence of normal serum residue. CONCLUSIONS: Hepatic uptake of SN-38 via OATP1B1 decreases in ESKD patients through cooperative inhibitory effects of UTs and serum components.