Trough Levels Research Articles

Therapeutic Drug Monitoring for Sirolimus in Children with Vascular Anomalies: What Can We Learn from a Retrospective Study.

Objectives: Sirolimus (SRL), a mammalian target of rapamycin inhibitor, has been widely used to treat patients with vascular anomalies (VAs). The objectives of this study were to summarize the routine blood SRL monitoring data for VAs children, to investigate the factors contributing to the variable blood SRL concentrations and to evaluate the efficacy and safety of SRL therapy. Methods: VAs patients with routine blood SRL monitoring from July 2017 to April 2022 at the Department of Burns and Plastic Surgery, Children's Hospital of Nanjing Medical University were retrospectively collected. Clinical data were obtained from the hospital information system. Results: In total, 67 children (35 females) were enrolled. The therapeutic drug monitoring data showed that the range of measured blood trough concentrations (Ctrough) was 3.6-46.8 ng/mL. At the initial measurements, only 33% of patients were in the target concentration range (10-15 ng/mL). But this proportion became 54% at the last measurements. The whole blood-Ctrough-to-daily dose (Ctrough/Dose) ratio was significantly associated with age and body weight (BW). The patients' laboratory results did not change significantly after SRL treatment. Although the incidence of adverse events was relatively high (44.8%), most of them were mild and tolerable. 70.3% patients had total responses to SRL, whereas 29.7% children exhibited stable disease or progressive disease. No significant differences were found in Ctrough between the total response group and non-response group. Conclusions: This retrospective study revealed a high variability in SRL blood concentrations in Chinese children with VAs. Of note, pediatric patients with older age and a higher BW had a lower Ctrough/Dose ratio. It is a concern whether the range of 10-15 ng/mL is feasible for Chinese children based only on our study. Further studies recruiting more patients are required to redefine the target reference range for children with VAs.

Challenges and potential solutions for cycloserine dosing in patients with sepsis undergoing continuous renal replacement therapy

Continuous kidney replacement therapy (CRRT) is a special form of dialysis, which has more significant advantages than traditional intermittent hemodialysis in treating critically ill patients. The impact of CRRT and disease complexity on drug clearance in critically ill patients has been reported in several studies, nevertheless, the pharmacokinetic changes of cycloserine in patients with sepsis undergoing CRRT have not been reported. Here, we report a case of a 52-year-old man with septic shock and severe multidrug-resistant tuberculosis who underwent anti-TB therapy. The patient's anti-TB regimen included linezolid, clofazimine, cycloserine, and bedaquiline. Following continuous administration for 14 days, the patient was treated with CRRT due to acid-base imbalance and acute renal failure. Blood samples were collected at 0, 2, 4, 6, 10, and 12 hours following cycloserine administration (CRRT was initiated two hours after administration). Changes in plasma concentration of cycloserine before and after the CRRT were measured. The peak concentration of cycloserine was 39.93 mg/L with a trough concentration of 7.90 mg/L, and the AUC0-12h was 294.36 mg•h/L. These findings firstly suggested that the pharmacokinetics of cycloserine may be influenced by sepsis and CRRT therapy, and cycloserine doses may need to be increased during CRRT therapy in patients with sepsis.

Exposure–response relationships of mirvetuximab soravtansine in patients with folate receptor‐α‐positive ovarian cancer: Justification of therapeutic dose regimen

AimsThis study aimed to investigate exposure–response (ER) relationships in efficacy and safety for mirvetuximab soravtansine (MIRV) which is a first‐in‐class antibody–drug conjugate approved for the treatment of folate receptor‐α‐positive platinum‐resistant ovarian cancer.MethodsMIRV was characterized in 4 clinical studies. Exposure metrics for MIRV, its payload and a metabolite were derived from a population pharmacokinetic model. Efficacy was analysed in MIRV‐treated patients (n = 215) in a recent confirmatory, randomized, chemotherapy‐controlled MIRASOL trial and safety was evaluated in patients pooled across all 4 clinical studies (n = 757).ResultsIn the MIRASOL trial (NCT04209855), MIRV demonstrated significant benefit over chemotherapy in progression‐free survival (PFS), objective response rate (ORR) and overall survival (OS). The most common adverse events (AEs) included ocular disorders, peripheral neuropathy and pneumonitis. For PFS, ORR and OS, the trough concentration of MIRV was the predictor consistently found in ER models for efficacy. In contrast, for ocular AEs (as well as the time to onset of ocular AEs) and peripheral neuropathy, the area under the concentration–time curve (AUC) of MIRV was identified as the exposure metric in ER models for safety. No exposure parameters were found to correlate with pneumonitis. Covariates in all models did not show clinically meaningful impact on efficacy or safety. Logistic regression models for ORR and ocular AEs based on AUC of MIRV were used to justify the clinical dose regimen approved for MIRV.ConclusionThe trough concentration of MIRV correlated with efficacy whereas the AUC of MIRV was associated with major AEs. The ER relationships supported the selected therapeutic dose regimen.

Optimizing tacrolimus dosing in Hispanic renal transplant patients: insights from real-world data.

Tacrolimus, an immunosuppressant used to prevent organ rejection in renal transplant patients, exhibits high inter-patient variability, necessitating therapeutic drug monitoring. Early post-transplant tacrolimus exposure in Hispanics is understudied. Although genotypic information is linked to pharmacokinetic differences, its clinical application remains limited. This study aimed to use a real-world data-driven, pharmacokinetic model-based approach for tacrolimus in Hispanics to determine a suitable initial dose and design an optimal dose titration strategy by simulations to achieve plasma trough concentration target levels of 10-12ng/mL at the earliest. Sparse concentration-time data of tacrolimus were obtained from electronic medical records for self-identified Hispanic subjects following renal transplant. Rich pharmacokinetic literature data was leveraged to estimate structural pharmacokinetic model parameters, which were then fixed in the current analysis. Only apparent clearance was estimated with the sparse tacrolimus data and potential covariates were identified. Simulations of various starting doses and different dose titration strategies were then evaluated. The analysis included 121 renal transplant patients with 2,215 trough tacrolimus concentrations. A two-compartment transit absorption model with allometrically scaled body weight and time-varying hematocrit on apparent clearance adequately described the data. The estimated apparent clearance was 13.7L/h for a typical patient weighing 70kg and at 30% hematocrit, demonstrating a 40% decrease in clearance compared to other patient populations. Model based simulations indicated the best initial dose for the Hispanic population is 0.1mg/kg/day. The proposed titration strategy, with three dose adjustments based on trough levels of tacrolimus, increased the proportion of patients within the target range (10-12ng/mL) more than 2.5-fold and decreased the proportion of patients outside the therapeutic window by 50% after the first week of treatment. Hispanic renal transplant population showed an estimated 40% decrease of apparent clearance in the typical patient compared to other populations with similar characteristics. The proposed dose adjustment attained the target range rapidly and safely. This study advocates for tailored tacrolimus dosing regimens based on population pharmacokinetics to optimize therapy in Hispanic renal transplant recipients.

Virological History Predicts Non-sustained Viral Suppression With Long-Acting Cabotegravir and Rilpivirine Therapy, Independent of Pharmacokinetic Parameters

Abstract Background This study aimed to investigate factors contributing to non-sustained viral suppression, including intermittent viremia and persistent low-level viremia, during cabotegravir (CAB) plus rilpivirine (RPV) long-acting (LA) injectable therapy, with a focus on pharmacokinetics (PK). Methods A prospective cohort study was conducted on people with human immunodeficiency virus (HIV, PWH) transitioning from stable oral antiretroviral therapy (ART) to bimonthly CAB + RPV LA. Standardized follow-up included close monitoring through blood sampling for plasma human immunodeficiency virus type 1 (HIV-1) viral load (VL) and multiple plasma drug concentrations measurements to analyze the connection between PK parameters and virologic outcomes. Results Among 173 patients with a median (interquartile range [IQR]) follow-up of 11.1(7.1–13.2) months and 789 pre-dose measurements, 38.7% experienced VL ≥ 20 copies/mL, and 16.2% had levels ≥50 copies/mL. Intermittent viremia occurred in 34.7% of patients, and persistent low-level viremia in 4%. Virological failure developed in 2 cases. Predictors of non-sustained viral suppression included VL at HIV diagnosis (adjusted hazard ratio [AHR]: 1.49 per log10 VL, 95% confidence interval [CI]: 1.04–2.12, P = .027), detectable viremia on oral ART (AHR: 2.45, 95% CI: 1.29–4.65, P = .006), and the level of viral suppression at transition (AHR: 0.38, 95% CI: .19–.75, P = .004). We found a significant association between low trough concentrations of CAB and RPV and episodes of detectable viremia exceeding 50 copies/mL. However, none of the assessed PK covariates predicted non-sustained viral suppression in multivariable models. Conclusions Non-sustained viral suppression in PWH transitioning from stable oral ART to CAB + RPV LA was linked to preexisting factors before transition. Higher VL pre-ART and incomplete suppression on oral therapy increased the risk, independent of PK parameters.

Physiologically-Based Pharmacokinetic Modeling of Total and Unbound Valproic Acid to Evaluate Dosing in Children With and Without Hypoalbuminemia.

Valproic acid (VPA) demonstrates nonlinear pharmacokinetics (PK) due to a capacity-limited protein binding, which has potential implications on its total and unbound plasma concentrations, especially during hypoalbuminemia. A physiologically based pharmacokinetic (PBPK) model was developed to assess the nonlinear dose-exposure relationship of VPA with special emphasis on pediatric patients with hypoalbuminemia. A PBPK model was first developed and evaluated in adults using PK-Sim® and MoBi® (v.11) and the scaled to children 1 year and older. The capacity-limited protein binding was characterized by second-order kinetics between VPA and albumin with a 2:1 molar ratio. All drug-specific parameters were informed by literature and optimized using published PK data of VPA. PK simulations were performed in virtual populations with normal and low albumin levels. The reported concentration-time profiles of total and unbound VPA were adequately predicted by the PBPK model across the age and dose range (3-120 mg/kg). The model was able to characterize the nonlinear PK, as the concentration-dependent fraction unbound (fu) and the related dose-dependent clearance values were well predicted. Simulated steady-state trough concentrations of total VPA were less than dose-proportional and were within the therapeutic drug monitoring range of 50-100 mg/L for doses between 30 and 45 mg/kg per day in children with normal albumin concentrations. However, virtual children with hypoalbuminemia largely failed to achieve the target exposure. The PBPK model helped assess the nonlinear dose-exposure relationship of VPA and the impact of albumin concentrations on the achievement of target exposure.

Intraperitoneally Administered Vancomycin Results in Suboptimal Serum and Peritoneal Effluent Drug Levels in Patients with PD-related Peritonitis

Background Intraperitoneal vancomycin is commonly used to treat peritoneal dialysis (PD)-related peritonitis. Therapeutic drug level monitoring helps optimize the use of vancomycin in CKD patients. We studied whether sufficient serum levels were achieved in patients with PD-related peritonitis treated with the commonly used dose of vancomycin in patients with end stage renal disease. Materials and Methods All consecutive patients with PD-related peritonitis during 19 months were studied. Patients received IP Vancomycin 15 mg/kg Q96H and amikacin 2 mg/kg while awaiting culture reports. Vancomycin concentration in serum and dialysate was determined by a validated liquid chromatography-tandem mass spectrometry assay at 1, 12, 24, and 96 h. The primary outcome was the drug levels in serum and peritoneal fluid, and the secondary outcome was peritonitis treatment failure. Results A total of 45 episodes of PD-related peritonitis were treated, of which 41 fulfilled the inclusion criteria and were included in the PK analysis. Recommended serum vancomycin trough level of >15 mg/L was achieved in only two cases. Twenty-one episodes required catheter removal. Conclusion In patients with PD-related peritonitis, intermittent intraperitoneal administration of 15 mg/kg of vancomycin every 96 h does not achieve the recommended serum and dialysate levels of vancomycin. There is an urgent need for pharmacokinetic studies on commonly used IP antibiotics in the PD population to facilitate correct dose recommendations.

The Relationship Between Weight Indices and Blood Levels of Immunosuppressive Drugs in Renal Transplant Recipients

Background: Calcineurin inhibitors and mammalian target of rapamycin (mTOR) inhibitors are essential for maintaining transplanted organs. However, determining the appropriate dosage and predicting blood concentrations of these drugs based solely on net body weight may be inadequate. Previous studies have presented contradictory results regarding the impact of obesity on drug concentrations and transplant success. Objectives: This study aims to evaluate various weight indices to identify the most reliable indicator of weight that correlates with the blood levels of drugs used in organ transplantation. Methods: This retrospective descriptive study included patients from nephrology clinics affiliated with Isfahan University of Medical Sciences who were taking calcineurin and/or mTOR inhibitor drugs. Data extracted from medical records included demographic and clinical information, such as height, weight, and various weight indices (total/ideal/adjusted body weight, lean body mass (LBM), Body Mass Index, and predicted normal weight), as well as blood levels of immunosuppressive drugs at each patient's visit. The dosages of each drug (mg/kg) were analyzed to determine which weight indices best correlated with the obtained blood concentrations, using the Generalized Estimating Equation (GEE) model with logistic regression, an independent correlation matrix, and a binary distribution for data analysis. Results: The study analyzed the medical records of 71 patients. Trough (C0) concentrations of drugs were evaluated in relation to each weight index, and odds ratios (OR) were calculated for statistical comparison. All weight indices increased the likelihood of achieving appropriate concentrations for cyclosporine, tacrolimus, and sirolimus. Drug dosing based on LBM (OR: 1.028), ideal body weight (OR: 1.075), and total body weight (OR: 1.041) showed the strongest correlations with achieving proper blood levels for cyclosporine, tacrolimus, and sirolimus, respectively. Conclusions: Integrating various weight indices for calculating individualized doses (mg/kg) of each immunosuppressive drug increases the likelihood of achieving appropriate blood concentrations. However, the optimal weight index varies for each drug. Further studies, particularly those incorporating therapeutic drug monitoring (TDM) plans in transplant centers, are warranted to validate and generalize these findings, providing a potential avenue for improving immunosuppressive therapy and enhancing transplant outcomes.

Interinstitutional Comparison of Vancomycin Area Under the Concentration-Time Curve Estimation in Korea: Need for Standardized Operational Protocols for Therapeutic Drug Monitoring Consultation.

Vancomycin, a vital antibiotic for treating gram-positive bacterial infections, requires therapeutic drug monitoring (TDM) because of its substantial pharmacokinetic variability. While traditional TDM relies on steady-state trough concentrations, recent guidelines advocate the area under the concentration-time curve (AUC) as the target index. However, detailed protocols for AUC estimation are lacking, leading to potential discrepancies among institutions. We surveyed medical institutions in Korea regarding vancomycin TDM, including AUC estimation. Nineteen participants responded to the TDM case challenge under three patient scenarios. For an ordinary patient in Case 1, the overall CV for AUC values was 0.4% when both trough and peak concentrations were included in the AUC calculation and 1.9% when utilizing only the trough concentration. For Case 2, an older patient with obesity, the corresponding CV was 6.6%. For Case 3 with multiple trough concentrations, the CV was 15.6%, reflecting variations in the selective use of data. Although the agreements in Case 1 were good, significant variability in AUC estimation was noted in cases involving atypical patient characteristics or old TDM data. Our study provides insight into the current status of vancomycin TDM in Korea and underscores the need for standardized operational protocols for AUC estimation.

Optimizing outcomes with maintenance IV UST in highly bio-exposed patients with IBD. Efficacy and adjusted regimen in real world

Background and aimsUstekinumab is an effective treatment for inflammatory bowel diseases. However, some patients do not respond to conventional doses. The aim of the study was to evaluate the effectiveness of intravenous maintenance ustekinumab in patients with secondary failure. MethodsSingle-center, retrospective study in adult patients with intravenous maintenance ustekinumab. The reduction of biochemical activity markers, ustekinumab trough levels and clinical indices of activity were evaluated. Biological remission was defined as the percentage decrease fecal calprotectin ≥80% and/or final fecal calprotectin ≤250 and C reactive protein <5mg/L. ResultsThirty-one patients were included: Crohn's disease 77.4%. All included patients were bio-exposed and 61.3% had carried ≥2 biologics.Pre-intravenous maintenance mean Harvey–Bradshaw Index was 6.5±4.38 vs 5±3.1 at week 8 (p=0.024) vs 4.1±3.1 at week 24 (p=0.019). The median ustekinumab trough level pre-intravenous maintenance was 1.40μg/ml [IQR 2.3] vs 5.35μg/ml [IQR 4.1] at week 8 (p<0.001) vs 4.8μg/ml [IQR 3.9] at week 24 (p<0.001). The pre-intravenous maintenance median fecal calprotectin was 809μg/g [IQR: 2256] vs 423μg/g [IQR: 999] at week 8 (p=0.025) vs 333μg/g [508] (p=0.001) at week 24.At the end of follow-up 48% went into biological remission. The presence of perianal disease was associated with lower biological remission (70.6% vs 27.3%, p=0.025). Median intravenous ustekinumab maintenance time was 8.55 [IQR 23.9] months. In 83.9% of patients no serious infections or malignancy were documented. ConclusionsThe use of maintenance intravenous ustekinumab appears to be an effective and safe strategy that can be evaluated as a salvage treatment especially in highly bio-exposed patients.

Population pharmacokinetics of unbound cefazolin in infected hospitalized patients requiring intermittent high-flux haemodialysis: can a three-times-weekly post-dialysis dosing regimen provide optimal treatment?

To describe the population pharmacokinetics of cefazolin in infected hospitalized patients requiring intermittent haemodialysis (IHD). This prospective population pharmacokinetic study was conducted in IHD patients prescribed cefazolin 2 g three times weekly. Plasma samples were collected at prespecified timepoints and assayed for total and unbound concentrations using validated LC. Pharmacokinetic modelling and dosing simulations were performed using Pmetrics®. PTA in plasma suitable for MSSA (unbound trough concentrations of ≥2 mg/L for the final 24 h of a 72 h interval) were simulated for different dosing regimens. A PTA of ≥95% was deemed acceptable. A total of 260 cefazolin concentrations (130 total, 130 unbound) were collected from 16 patients (14 female) with a median age of 51 years. The median (IQR) pre-dialysis unbound cefazolin concentration for a 3 day dose interval trough was 17.7 (13.5-31.4) mg/L. The median (IQR) unbound fraction was 0.38 (0.32-0.46). The lowest pre-dialysis unbound concentration was 9.1 mg/L. A two-compartment model with a complex protein-binding component adequately described the data. The mean unbound cefazolin CL during IHD was 16.4 ± 4.26 L/h, compared with 0.40 ± 0.19 L/h when dialysis was off. Duration of time on haemodialysis (TOH) was the only covariate supported in the final model. The 2 g three-times-weekly regimen was associated with a PTA of 99.7% on dosing simulations to maintain unbound concentrations of ≥2 mg/L with TOH of 6 months. The 1 g three-times-weekly post-dialysis was associated with a PTA of 95.4%. A 2 g three-times-weekly post-dialysis cefazolin regimen is supported for MSSA infections.

Effectiveness and safety of glucose-lowering drugs as an adjunct to insulin therapy in Chinese patients with type 1 diabetes: a retrospective, observational study.

To assess the real-world impact of glucose-lowering drugs (GLDs) as an adjunct to insulin in Chinese patients with type 1 diabetes (T1DM). This dual-center, observational, retrospective study included 121 T1DM patients receiving GLDs as adjuncts and 56 participants with insulin-only drugs as comparators. Glycated hemoglobin A1c (HbA1c), daily insulin dosage, fasting blood glucose (FBG), postprandial blood glucose (PBG), nocturnal blood glucose (NBG) and the difference in trough and peak blood glucose levels on the same day (Δ TP) were assessed at baseline and at the end of the study. In total, HbA1c decreased by 1.14% in the GLD+insulin group (p < 0.0001) and 0.36% in the insulin-only group (p = 0.0423, mean adjusted difference, -0.09% [95% CI, -0.55 to 0.37]). The total daily insulin concentration was reduced by 7.34 U per day in the GLD+insulin group vs. 5.55 U per day in the insulin-only group (mean adjusted difference, -2.32 U [95% CI, -4.97 to 0.33]). In particular, among patients with fasting C-peptide levels < 17 pmol/L, the total daily insulin concentration was significantly reduced by 9.22 U vs. 5.09 U per day (mean adjusted difference, -3.84 [95% CI, -6.85-0.84]; p = 0.0129). There were no notable differences in the other glycemic indices between the two groups. A gradual downward trend in changes in glycemic outcomes was observed among patients treated with various combinations of metformin, acarbose, and dipeptidyl peptidase 4 inhibitor (DPP-4i). Similar reductions in the daily insulin dose were also detected in most of the GLD+insulin group in addition to the DPP-4i-only group. No severe hypoglycemia was induced by additional GLDs. The use of additional GLDs tends to improve glycemic outcomes and reduce insulin requirements in patients with T1DM. These results indicate that the use of GLDs as an adjunctive therapy may have been an effective treatment strategy among adults with T1DM in China.

Approaches for posaconazole therapeutic drug monitoring and their clinical benefits.

This review examines the progress of research on posaconazole therapeutic drug monitoring (TDM) that has focused on differences in the TDM of posaconazole after clinical application in different formulations and in different populations, the factors that affect posaconazole concentrations, the advantages of posaconazole TDM in terms of clinical efficacy and cost savings, and measurement methods. A literature search (2006 to 2024) was performed in PubMed and Embase with the following search terms: noxafil, posaconazole hydrate, posaconazole, drug monitoring, therapeutic drug monitoring, and TDM. Abstracts of review articles, prospective studies, and retrospective studies were reviewed. TDM should be implemented earlier for posaconazole tablets and injections than for oral posaconazole suspensions. Posaconazole TDM is beneficial for improving clinical efficacy, and the incidence of breakthrough invasive fungal infections (IFIs) can be significantly reduced by gradually adjusting the posaconazole dose in response to TDM in patients with inadequate trough concentrations. Early TDM allows more patients to achieve target therapeutic posaconazole concentrations. TDM can also facilitate dose adjustments, which reduce the cost of this expensive drug. Different assay techniques, including chromatography, microbiological detection, chemofluorimetry, paper spray mass spectrometry, and capillary electrophoresis, can be used for posaconazole TDM. Posaconazole TDM has potential clinical utility and cost-saving benefits and could improve the outcomes of IFI treatment.

A phase 3, randomized, double-blind, active-controlled clinical trial to compare BAT1806/BIIB800, a tocilizumab biosimilar, with tocilizumab reference product in participants with moderate-to-severe rheumatoid arthritis with inadequate response to methotrexate: treatment period 2 analysis (week 24 to week 48)

BackgroundEquivalent efficacy and comparable pharmacokinetic, immunogenicity, and safety profiles of the biosimilar BAT1806/BIIB800 and reference tocilizumab (TCZ) in participants with moderate-to-severe rheumatoid arthritis (RA) have been reported up to week 24 (treatment period [TP] 1) of the phase 3 study. Here we present results for TP2 (study weeks 24–48).MethodsIn this phase 3, multicenter, multiregional, double-blind, active-controlled, equivalence study, participants with active RA despite methotrexate were randomized (1:1:2) to intravenous administration of 8 mg/kg TCZ every 4 weeks to week 48 (TCZ group), or TCZ to week 24 followed by BAT1806/BIIB800 to week 48 (TCZ to BAT1806/BIIB800 group), or BAT1806/BIIB800 to week 48 (BAT1806/BIIB800 group). Efficacy in TP2 was evaluated using American College of Rheumatology (ACR) response criteria (ACR20/50/70) and change from baseline in Disease Activity Score on 28 joints (DAS28). Pharmacokinetics (trough levels), safety, and immunogenicity were also evaluated.ResultsOf 621 randomized participants, 577 (92.9%) completed TP1 and entered TP2 (TCZ: N = 145 [93.5%]; TCZ to BAT1806/BIIB800: N = 142 [92.2%]; BAT1806/BIIB800: N = 290 [92.9%]). Proportions of ACR20 responders were similar between treatment groups throughout TP2 (87.8%, 90.3%, and 90.4%, respectively, at week 48), as were proportions of ACR50 and ACR70 responders, and reduction in DAS28. Drug trough levels and antidrug antibody incidences were comparable between the treatment groups. Adverse events were balanced across the treatment groups and no fatal events were reported.ConclusionIn TP2, efficacy, safety, immunogenicity, and pharmacokinetic profiles were comparable between the TCZ, TCZ to BAT1806/BIIB800, and BAT1806/BIIB800 groups.Trial registrationNCT03830203 and EudraCT 2018-002202-31.

Voriconazole therapeutic drug monitoring including analysis of CYP2C19 phenotype in immunocompromised pediatric patients with invasive fungal infections

PurposeTherapeutic drug monitoring (TDM) of voriconazole (VCZ) should be mandatory for all pediatric patients with invasive fungal infections (IFIs). The narrow therapeutic index, inter-individual variability in VCZ pharmacokinetics, and genetic polymorphisms cause achieving therapeutic concentration during therapy to be challenging in this population.MethodsThe study included 44 children suffering from IFIs treated with VCZ. Trough concentrations (Ctrough) of VCZ ware determined by the HPLC-FLD method. Identification of the CYP2C19*2 and CYP2C19*17 genetic polymorphisms was performed by PCR–RFLP. The correlation between polymorphisms and VCZ Ctrough was analyzed. Moreover, the effect of factors such as dose, age, sex, route of administration, and drug interactions was investigated.ResultsVCZ was administered orally and intravenously at a median maintenance dosage of 14.7 mg/kg/day for a median of 10 days. The VCZ Ctrough was highly variable and ranged from 0.1 to 6.8 mg/L. Only 45% of children reached the therapeutic range. There was no significant association between Ctrough and dosage, age, sex, route of administration, and concomitant medications. The frequencies of variant phenotype normal (NM), intermediate (IM), rapid (RM) and ultrarapid metabolizers (UM) were 41%, 18%, 28%, and 13%, respectively. Ctrough of VCZ were significantly higher in NM and IM groups compared with RM, and UM groups.ConclusionThe Ctrough of VCZ is characterized by inter-individual variability and a low rate of patients reaching the therapeutic range. The significant association exists in children between VCZ Ctrough and CYPC19 phenotype. The combination of repeated TDM and genotyping is necessary to ensure effective treatment.

Pharmacokinetic model-based assessment of factor IX prophylaxis treatment regimens in severe hemophilia B

An important aspect of improving care for people with hemophilia B (HB) is developing optimal treatment strategies. Here we aimed to provide in-silico evidence, comparing the estimated optimal posology of factor IX (FIX) products to support the patient-physician decision-making process. A population pharmacokinetic (popPK) model-based assessment comparing the performance of FIX products (rFIX, rIX-FP, rFIXFc, N9-GP) was developed. PopPK analyses were used to determine a product’s optimal posology to target predefined steady-state FIX activity trough levels in a hypothetical population of 10,000 people with severe HB. Model-derived optimal posologies were compared across several parameters including trough levels, proportion of patients per regimen and consumption, considering 64 hypothetical patient scenarios of different FIX trough level targets and ages. Results indicated a marked difference between FIX products estimated to achieve target trough levels, consumption and dosing frequencies. rIX-FP was associated with higher trough levels than rFIX and rFIXFc, at a lower weekly dose and administration frequency, across all age groups. N9-GP use in adolescents and adults was associated with lower consumption compared with rIX-FP. Insights from this study may be utilized by clinicians to inform decision-making, by considering the model-generated estimated optimal posologies alongside multiple clinical factors and patient preferences.

Pharmacokinetic and Pharmacodynamic Assessment of Valganciclovir in Infants With Congenital Cytomegalovirus Infection.

Valganciclovir (VGCV) is administered at a dose of 16 mg/kg 2 times daily for 6 months to treat symptomatic congenital cytomegalovirus (CMV) infections. During the treatment period, approximately 20% of the patients developed grade 3 or higher neutropenia. Currently, information on the pharmacokinetics and pharmacodynamics of ganciclovir, an active metabolite of VGCV, in infants is limited. In the current study, the relationship between ganciclovir concentration and neutropenia was investigated, and a population pharmacokinetic (PPK) model of ganciclovir in infants with symptomatic congenital CMV infection was developed. Japanese infants who were prescribed oral VGCV for symptomatic congenital CMV infections between July 2017 and January 2021 were included. The relationship between the observed trough ganciclovir concentrations and neutrophil counts was examined. PPK analysis was performed to evaluate the covariates affecting the pharmacokinetics of ganciclovir. Twenty-seven ganciclovir serum samples from 8 patients were analyzed. A moderate negative correlation was observed between the observed trough ganciclovir concentration and neutrophil count. PPK model analysis showed that postmenstrual age (PMA) affected the total body clearance of ganciclovir after correcting for the empirical allometric scaling of body weight. Based on PMA and body weight, a nomogram to achieve the target area under the concentration-time curve from 0 to 24 hours of 40-60 mcg·h·mL-1 of ganciclovir was calculated. The relationship between neutrophil count and ganciclovir trough concentration in infants was clarified. The PPK model showed that the dose of VGCV should be reduced in patients with a low PMA to achieve target exposure.

Pharmacokinetics, Safety and Tolerability of Single-dose or Multiple-dose Cefiderocol in Hospitalized Pediatric Patients Three Months to Less Than Eighteen Years Old With Infections Treated With Standard-of-care Antibiotics in the PEDI-CEFI Phase 2 Study.

Multidrug-resistant Gram-negative bacterial infections are increasing globally in neonates, infants and children; antibiotic options are limited. This international, multicenter, open-label phase 2 study, investigated the pharmacokinetics, safety and tolerability of single-dose and multiple-dose cefiderocol [as a 3-hour infusion (every 8 hours) dosed at 2000 mg for body weight ≥34 kg and at 60 mg/kg for body weight <34 kg], over a range of renal function, in hospitalized pediatric patients with aerobic Gram-negative bacterial infection; multiple-dose patients required standard-of-care systemic antibiotics for 5-14 days. Four cohorts of pediatric patients were enrolled (cohort 1: 12 to <18 years, cohort 2: 6 to <12 years, cohort 3: 2 to <6 years and cohort 4: 3 months to <2 years). A total of 53 patients (median age: 73.5 months) were enrolled. Plasma concentration profiles were similar with single-dose (n = 24) and multiple-dose (n = 29) cefiderocol, irrespective of age and body weight in those with normal renal function or mild renal impairment. Geometric mean concentrations at the end of infusion ranged between 72.7 and 97.1 μg/mL for single-dose cefiderocol and between 88.8 and 106.0 μg/mL after multiple doses. At 8 hours, corresponding trough concentrations ranged from 7.86 to 10.8 μg/mL with single-dose cefiderocol and from 9.64 to 18.1 μg/mL with multiple doses. There were no deaths, no cefiderocol-related serious adverse events, significant related laboratory abnormalities or discontinuations. Multiple-dose cefiderocol, administered for 5-14 days and according to body weight, achieved steady-state plasma concentrations that remained above the susceptibility breakpoints of Gram-negative bacteria throughout the dosing period. Cefiderocol was well tolerated.

Drug-drug interaction between diltiazem and tacrolimus in relation to CYP3A5 genotype status in Chinese pediatric patients with nephrotic range proteinuria: a retrospective study.

Tacrolimus is widely used to treat pediatric nephrotic range proteinuria (NRP). Diltiazem, a CYP3A4/5 inhibitor, is often administered with tacrolimus, affecting its pharmacokinetic profile. The impact of this combination on tacrolimus exposure, particularly in CYP3A5*3 genetic polymorphism, remains unclear in pediatric NRP patients. This study aimed to evaluate the effects of diltiazem on tacrolimus pharmacokinetics, focusing on the CYP3A5*3 polymorphism. We conducted a retrospective clinical study involving pediatric NRP patients, divided into two groups: those receiving tacrolimus with diltiazem and those receiving tacrolimus alone. Propensity score matching (PSM) was used to balance the baseline characteristics between the groups. We compared daily dose-adjusted trough concentrations (C0/D) of tacrolimus in both the original and PSM cohorts. The influence of diltiazem on tacrolimus C0/D, stratified by CYP3A5*3 genetic polymorphism, was assessed in a self-controlled case series study. Before PSM, the tacrolimus C0/D in patients taking diltiazem was significantly higher compared to those with tacrolimus alone (75.84 vs. 56.86ng/mL per mg/kg, P = 0.034). This finding persisted after PSM (75.84 vs. 46.93ng/mL per mg/kg, P= 0.028). In the self-controlled case study, tacrolimus C0/D elevated about twofold (75.84 vs. 34.76ng/mL per mg/kg, P < 0.001) after diltiazem administration. CYP3A5 expressers (CYP3A5*1/*1 and *1/*3) and CYP3A5 non-expressers (CYP3A5*3/*3) experienced a 1.8-fold and 1.3-fold increase in tacrolimus C0/D when combined with diltiazem, respectively. Diltiazem significantly increased tacrolimus C0/D, with CYP3A5*3 expressers showing higher elevations than non-expressers among pediatric NRP patients. These findings highlight the importance of personalized tacrolimus therapy based on CYP3A5*3 genotypes in pediatric patients taking diltiazem.

A Pharmacologic Evaluation of Buprenorphine in Pregnancy and the Postpartum Period.

The dosing regimen in the package insert for sublingual buprenorphine is similar for pregnant and nonpregnant people despite the physiologic changes seen during pregnancy. To compare plasma buprenorphine pharmacokinetics during and after pregnancy and relate buprenorphine concentration to the pharmacodynamic endpoints of pupil diameter, Clinical Opioid Withdrawal Scale (COWS), and craving scores. Prospective cohort of 22 pregnant people undergoing 33 pharmacologic studies (6-8 hours each) during pregnancy or postpartum. Participants were on a stable daily dose of 2-8 mg sublingual buprenorphine every 6 or 8 hours. The dosing frequency was selected by the participant. On study day, baseline measurements of plasma buprenorphine, pupil diameter, COWS, and craving scores were obtained, then the usual morning dose was taken, and measurements were repeated several times over 1 dosing interval. The dose-normalized area under the plasma buprenorphine concentration time curve was significantly (P = 0.036) lower during pregnancy (155 ± 52 ng × min/mL) than postpartum (218 ± 113 ng × min/mL). Buprenorphine trough concentrations were similar at the start (1.1 ± 0.7 ng/mL) and end of a dosing cycle (1.2 ± 0.8 ng/mL) regardless of dosing frequency. Pupillary diameter, COWS, and craving scores returned to baseline as buprenorphine concentrations approached ~1 ng/mL. Pregnant people require a higher dose of buprenorphine to achieve concentrations comparable to nonpregnant people. There is a temporal relationship between the plasma buprenorphine concentration and the pharmacodynamic markers of pupillary diameter, COWS, and craving scores. An average plasma concentration of ~1 ng/mL was associated with the lowest level of COWS and craving scores.