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.

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.

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.

Investigation of severe acute respiratory syndrome coronavirus 2 infection status in solid organ transplant recipients treated with tixagevimab/cilgavimab.

INTRODUCTION: Tixagevimab and cilgavimab (T/C) are neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that can be used to prevent SARS-CoV-2 infection in solid organ transplant (SOT) recipients. However, their neutralizing activity against recent variants was reduced, raising concerns regarding the emergence of breakthrough coronavirus diseases 2019 (COVID-19). This study aimed to investigate the status of the COVID-19 breakthrough after T/C administration. METHODS: We retrospectively investigated breakthrough COVID-19 in SOT recipients administered T/C at Kyoto University Hospital, Japan, from November 2022 to March 2023. Patients were monitored for 6 months after T/C administration. SARS-CoV-2 infection was diagnosed using polymerase chain reaction or antigen tests. The monthly incidence rates of SARS-CoV-2 infection were calculated using the person-time method. RESULTS: T/C were administered to 67 SOT recipients (liver, 16; lung, 36; and kidney, 15), of whom five were infected with SARS-CoV-2. All five cases were classified as mild, and none of these patients required admission to the intensive care unit (ICU) or died. All infected individuals tested positive for SARS-CoV-2 after March 2023, when T/C-resistant subvariant strains became predominant. The monthly incidence rate of SARS-CoV-2 infection, calculated using the person-time method, suggested an increasing trend. CONCLUSIONS: During the T/C-resistant variant epidemic, SARS-CoV-2 infections were identified even after T/C administration, suggesting that the prophylactic effects of T/C were invalid. Therefore, emerging variants must be carefully monitored and characterized to determine appropriate antiviral strategies, such as the use of suitable neutralizing antibodies.

Comparison of the safety and cost-effectiveness of nebulized liposomal amphotericin B and amphotericin B deoxycholate for antifungal prophylaxis after lung transplantation.

INTRODUCTION: Fungal infection after lung transplantation can lead to poor clinical outcome, for which lung transplant recipients require prophylaxis. One of the antifungal agents used after lung transplantation is nebulized amphotericin B (AMB). Nebulized AMB causes adverse events such as dyspnea and airway irritation, and long-term use leads to high economic costs. So far, prophylactic regimens employing AMB deoxycholate (AMB-d) and liposomal AMB (L-AMB) have been developed. This study compared the efficacy, safety, and cost of AMB-d and L-AMB. PATIENTS AND METHODS: Patients who underwent lung transplantation at Kyoto University Hospital from January 2021 to May 2023 were included in this study. Thirty-three patients received nebulized AMB-d, whereas 29 received nebulized L-AMB. RESULTS: Both regimens maintained comparable prophylactic efficacy regarding the development of fungal infection in the AMB-d and L-AMB groups (3.0% vs. 3.4%, P = 0.877). Patients treated with nebulized L-AMB experienced fewer respiratory-related adverse reactions than those treated with nebulized AMB-d (6.9% vs. 30.3%, P < 0.05), leading to a longer treatment duration with L-AMB than with AMB-d. Additionally, the daily cost of administering L-AMB was lower than that of administering AMB-d (3609 Japanese yen vs. 1792.3 Japanese yen, P < 0.05). DISCUSSION: These results suggest that nebulized L-AMB is safer and more cost-effective than nebulized AMB-d, with comparable efficacy.

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.

A case report of a prolonged decrease in tacrolimus clearance due to co-administration of nirmatrelvir/ritonavir in a lung transplant recipient receiving itraconazole prophylaxis.

BACKGROUND: Drug-drug interaction management is complex. Nirmatrelvir/ritonavir is a potent cytochrome P450 (CYP) 3A inhibitor and influences pharmacokinetics of co-administered drugs. Although there are several reports about drug-drug interactions of nirmatrelvir/ritonavir, an influence of a concomitant use of nirmatrelvir/ritonavir and another potent CYP3A inhibitor on tacrolimus remains unclear. Here, we experienced a lung transplant patient with the novel coronavirus disease 2019 (COVID-19). In this patient, nirmatrelvir/ritonavir was administered, and the inhibitory effect of itraconazole on CYP3A was prolonged. CASE PRESENTATION: We present a case in forties who had undergone lung transplantation. He was administered itraconazole and tacrolimus 1.0 mg/d, with a trough value of 8-12 ng/mL. The patient contracted the COVID-19, and a nirmatrelvir/ritonavir treatment was initiated. During the antiviral treatment, tacrolimus administration was discontinued for 5 d. Tacrolimus was resumed at 1.0 mg/d after completion of the nirmatrelvir/ritonavir treatment, but the trough value after 7 d was high at 31.6 ng/mL. Subsequently, the patient was placed on another 36-h tacrolimus discontinuation, but the trough value decreased to only 16.0 ng/mL. CONCLUSIONS: Co-administration of ritonavir caused a prolonged decrease in tacrolimus clearance through its inhibitory effects on CYP3A in a patient taking itraconazole. Management of drug-drug interaction by pharmacists can be important for patients with multiple medications.

Association between time in therapeutic range of tacrolimus blood concentration and acute rejection within the first three months after lung transplantation.

BACKGROUND: Tacrolimus is a key drug in immunosuppressive therapy following lung transplantation. The blood tacrolimus levels are likely to fluctuate in the early postoperative period, and failure to maintain the tacrolimus trough level in target ranges is a risk factor for rejection. However, there is little information about the relationship between the time in therapeutic range (TTR) of the tacrolimus trough level (tacrolimus TTR) and clinical outcomes. This study aimed to evaluate the association between tacrolimus TTR and acute rejection (AR) within the first three months after lung transplantation. METHODS: This was a retrospective study of patients who underwent lung transplantation at a single center. The target tacrolimus trough levels were 10-15 ng/mL, and tacrolimus TTR was calculated using the Rosendaal method. The cut-off value of the tacrolimus TTR was estimated by receiver operating characteristic analysis based on AR. RESULTS: The study included 90 patients. AR was observed in 26 patients. In this study, ''early-AR'' was defined as any AR within 2 weeks post-transplant (n = 22) and ''late-AR'' was defined as any AR after 1-month post-transplant (n = 4). For early AR, the relationship between tacrolimus TTR and the onset of AR was examined. There were no differences in the tacrolimus TTR between the early-AR group and non-AR group (35.7 ± 22.4 vs 31.5 ± 19.9%, P = 0.416). For late-AR, the relationship with tacrolimus TTR was examined every 10 d. The tacrolimus TTR during postoperative days (POD) 21-30 and POD 31-onset was significantly lower in the late-AR group than the no-AR group (50.0 ± 7.1 vs. 71.8 ± 18.0% and 37.0 ± 26.6 vs. 68.9 ± 31.5%, P < 0.05, respectively). The cutoff value of the tacrolimus TTR during POD 21-30 was estimated as 55.0%. CONCLUSIONS: Our findings suggest that a lower tacrolimus TTR is a predictor of late AR. A tacrolimus TTR of 55% or higher is necessary to reduce the risk of AR during this period after lung transplantation.

Improved absorption of itraconazole tablet by co-administration with lemon beverages in a lung transplant recipient: A case report.

After lung transplantation, itraconazole (ITCZ) is used as a prophylaxis for aspergillosis. ITCZ is a weak base with high lipophilicity, and the dissolution and absorption of ITCZ tablets and capsules are pH dependent. Therefore, ITCZ may not achieve sufficient serum concentrations in patients with higher gastric pH because of its poor bioavailability. We report a case of a woman in fifties with post-COVID-19 respiratory failure who successfully underwent lung transplantation, followed by improved bioavailability of ITCZ tablets when given with acidic lemon beverages. The patient was initially administered ITCZ oral solution; this was discontinued because of its unpleasant taste, nausea, and vomiting. The ITCZ oral solution was replaced with ITCZ tablets 78 days after transplantation; however, serum concentrations of ITCZ and hydroxy-ITCZ were below the detection limit (100 ng/mL). We co-administered ITCZ tablets with commercially available lemon beverages. Subsequently, serum concentrations of ITCZ and hydroxy-ITCZ increased to 341 and 673 ng/mL, respectively, on the 125th day after transplantation. Infection with fungi, including Aspergillus spp., was not observed in this case. The patient had no adverse events such as gastric ulcer or hyperglycemia. These results suggest that the co-administration of lemon beverages and ITCZ tablets may help achieve better absorption of ITCZ in patients taking acid suppressants.

Population pharmacokinetic modeling of GS-441524, the active metabolite of remdesivir, in Japanese COVID-19 patients with renal dysfunction.

Remdesivir, a prodrug of the nucleoside analog GS-441524, plays a key role in the treatment of coronavirus disease 2019 (COVID-19). However, owing to limited information on clinical trials and inexperienced clinical use, there is a lack of pharmacokinetic (PK) data in patients with COVID-19 with special characteristics. In this study, we aimed to measure serum GS-441524 concentrations and develop a population PK (PopPK) model. Remdesivir was administered at a 200 mg loading dose on the first day followed by 100 mg from day 2, based on the package insert, in patients with an estimated glomerular filtration rate (eGFR) greater than or equal to 30 ml/min. In total, 190 concentrations from 37 Japanese patients were used in the analysis. The GS-441524 trough concentrations were significantly higher in the eGFR less than 60 ml/min group than in the eGFR greater than or equal to 60 ml/min group. Extracorporeal membrane oxygenation in four patients hardly affected the total body clearance (CL) and volume of distribution (Vd ) of GS-441524. A one-compartment model described serum GS-441524 concentration data. The CL and Vd of GS-441524 were significantly affected by eGFR readjusted by individual body surface area and age, respectively. Simulations proposed a dose regimen of 200 mg on day 1 followed by 100 mg once every 2 days from day 2 in patients with an eGFR of 30 ml/min or less. In conclusion, we successfully established a PopPK model of GS-441524 using retrospectively obtained serum GS-441524 concentrations in Japanese patients with COVID-19, which would be helpful for optimal individualized therapy of remdesivir.

Risk factors of breakthrough aspergillosis in lung transplant recipients receiving itraconazole prophylaxis.

INTRODUCTION: Invasive Aspergillus infection (IA) in lung transplantation can result in poor outcomes. Itraconazole has been shown to be effective for fungal prophylaxis in lung transplant recipients. However, IA remains a major cause of death after lung transplantation. Therefore, we aimed to clarify the risk factors for IA on itraconazole prophylaxis. METHODS: We examined 120 recipients to uncover their IA epidemiology, clinical characteristics, and outcomes. In addition, a case-control study was performed to identify risk factors of IA. RESULTS: Of the 120 patients, 12 developed IA under itraconazole prophylaxis. The patient demographics and clinical characteristics were compared among the following two groups: IA group, 12 patients, and control group, 108 patients. Significant differences were observed in age (p = 0.004), history of interstitial pneumonia (p = 0.032), and CMV infection (p < 0.001) between the groups. Before the onset of IA, 92% (11/12) of the patients received itraconazole with trough concentrations above the therapeutic range. IA developed at 272.9 ± 114.1 days after lung transplantation. Of the 12 patients who developed IA, 66.7% (8/12) had early cessation of cytomegalovirus (CMV) prophylaxis due to toxicity of valganciclovir, as follows: leukocytopenia in 4 patients, and renal dysfunction in 4 patients. Of the 8 patients who stopped valganciclovir, 75% (6/8) developed CMV infection subsequently. CONCLUSION: This study suggests that older age, history of interstitial pneumonia, and CMV infection may be important risk factors for IA on itraconazole prophylaxis. These results may help clinicians optimize prophylactic strategies for IA.

Pharmacist-physician collaborative care for outpatients with left ventricular assist devices using a cloud-based home medical management information-sharing system: a case report.

BACKGROUND: The standard anticoagulation therapy for patients implanted with left ventricular assist devices (LVADs) includes warfarin therapy. We developed a cloud-based home medical management information-sharing system named as LVAD@home. The LVAD@home system is an application designed to be used on iPad tablet computers. This system enables the sharing of daily information between a patient and care providers in real time. In this study, we reported cases of outpatients with LVADs using this system to manage anticoagulation therapy. CASE PRESENTATION: The patient, a man in his 40s with end-stage heart failure owing to non-ischemic dilated cardiomyopathy, underwent LVAD implantation and warfarin was started on postoperative day 1. He started to use LVAD@home to manage warfarin therapy after discharge (postoperative day 47). He sent his data to care providers daily. By using this system, the pharmacist observed his signs of reduced dietary intake 179 days after discharge, and after consulting the physician, told the patient to change the timing of the next measurement earlier than usual. On the next day, the prothrombin time-international normalized ratio increased from 2.0 to 3.0, and thus the dose was decreased by 0.5 mg. Four patients used this system to monitor warfarin therapy from October 2015 to March 2018. In these patients, the time in therapeutic range was 90.1 ± 1.3, which was higher than that observed in previous studies. Additionally, there were no thromboembolic events or bleeding events. CONCLUSIONS: The cloud-based home management system can be applied to share real-time patient information of factors, including dietary intake that interact with warfarin. It can help to improve long-term anticoagulation outcomes in patients implanted with LVAD.

Effects of fasting on warfarin sensitivity index in patients undergoing cardiovascular surgery.

PURPOSE: Warfarin shows large inter- and intra-individual variabilities in its pharmacokinetics and pharmacodynamics. Sufficient understanding of factors affecting the response to warfarin is necessary to achieve improved outcomes for warfarin therapy. In this study, we evaluated effects of fasting on the anticoagulant properties of warfarin. METHODS: We conducted a retrospective observational study involving a total of 58 patients, who received cardiovascular surgeries and subsequent warfarin therapy. The effect of dietary intake on the anticoagulant properties with warfarin was assessed by measurement of the international normalized ratio of prothrombin time (PT-INR): the anticoagulant activities of warfarin were expressed as the warfarin sensitivity index (WSI). Additionally, fluctuations in WSI during the study period were obtained as differences between the maximum and minimum WSI. RESULTS: The maximum PT-INR and WSI values were significantly higher for patients who were fasting for different reasons during the postoperative period than those in the group without reduced dietary intake. The differences between maximum and minimum WSI in the fasting group significantly increased compared with those in the groups with moderate or no reduced dietary intake. Meanwhile, effects of other markers of clinical conditions including the baseline Child-Pugh score and Charlson Comorbidity Index on WSI were not significant. CONCLUSIONS: Our results indicate that postoperative fasting was significantly associated with the anticoagulation activity of warfarin. In patients fasting for different reasons during the postoperative period, closer control of PT-INR values and warfarin adjustments may be required to avoid adverse effects such as bleeding in warfarin treatment.

Synthesis, crystal structure, and physical properties of sterically unprotected hydrocarbon radicals.

We have prepared and isolated neutral polycyclic hydrocarbon radicals. A butyl-substituted radical gave single crystals, in which a π-dimeric structure, not a σ-bonded dimer, was observed, even though steric protection was absent. Thermodynamic stabilization due to the highly spin-delocalized structure contributes effectively to the suppression of σ-bond formation.