TDM-based Dose Research Articles

Role of TDM-Based Dose Adjustments For AC/T Regimen Drugs Used In Breast Carcinoma

Role of TDM-Based Dose Adjustments For AC/T Regimen Drugs Used In Breast Carcinoma

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

BackgroundGanciclovir 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 presentationIn 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.ConclusionsThe 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.

Treosulfan Exposure Predicts Thalassemia-Free Survival in Patients with Beta Thalassemia Major Undergoing Allogeneic Hematopoietic Cell Transplantation.

A toxicity-reduced conditioning regimen with treosulfan, fludarabine, and thiotepa in patients with high-risk β-thalassemia major has significantly improved hematopoietic stem cell transplantation (HCT) outcomes. However, complications resulting from regimen-related toxicities (RRTs), mixed chimerism, and graft rejection remain a challenge. We evaluated the dose-exposure-response relationship of treosulfan and its active metabolite S, S-EBDM, in a uniform cohort of patients with β-thalassemia major to identify whether therapeutic drug monitoring (TDM) and dose adjustment of treosulfan is feasible. Plasma treosulfan/S, S-EBDM levels were measured in 77 patients using a validated liquid chromatography with tandem mass spectrometry method, and the pharmacokinetic parameters were estimated using nlmixr2. The influence of treosulfan and S, S-EBDM exposure, and GSTA1/NQO1 polymorphisms on graft rejection, RRTs, chimerism status, and 1-year overall survival (OS), and thalassemia-free survival (TFS) were assessed. We observed that treosulfan exposure was lower in patients with graft rejection than those without (1,655 vs. 2,037 mg•h/L, P = 0.07). Pharmacodynamic modeling analysis to identify therapeutic cutoff revealed that treosulfan exposure ≥1,660 mg•hour/L was significantly associated with better 1-year TFS (97% vs. 81%, P = 0.02) and a trend to better 1-year OS (90% vs. 69%, P = 0.07). Further, multivariate analysis adjusting for known pre-HCT risk factors also revealed treosulfan exposure <1,660 mg•h/L (hazard ratio (HR) = 3.23; 95% confidence interval (CI) = 1.12-9.34; P = 0.03) and GSTA1*B variant genotype (HR = 3.75; 95% CI = 1.04-13.47; P = 0.04) to be independent predictors for inferior 1-year TFS. We conclude that lower treosulfan exposure increases the risk of graft rejection and early transplant-related mortality affecting TFS. As no RRTs were observed with increasing treosulfan exposure, TDM-based dose adjustment could be feasible and beneficial.

Mercaptopurine for the treatment of ulcerative colitis - a randomised placebo-controlled trial.

Scepticism about the efficacy of thiopurines for ulcerative colitis (UC) is rising.This study aimed to evaluate mercaptopurine treatment for UC. In this prospective, randomised, double-blind, placebo-controlled trial, patients with active UC, despite treatment with 5-aminosalicylates (5-ASA), were randomised for therapeutic drug monitoring (TDM)-guided mercaptopurine treatment or placebo for 52 weeks. Corticosteroids were given in the first eight weeks and 5-ASA was continued. Proactive metabolite-based mercaptopurine and placebo dose adjustments were applied from week six onwards by unblinded clinicians. The primary endpoint was corticosteroid-free clinical remission and endoscopic improvement (total Mayo score ≤2 points and no item >1) at week 52 in an intention-to-treat analysis. Between December 2016 and April 2021, 70 patients were screened and 59 were randomised at six centres. In the mercaptopurine group, 16/29 (55.2%) patients completed the 52-week study, compared to 13/30 (43.3%) on placebo. The primary endpoint was achieved by 14/29 (48.3%) patients on mercaptopurine and 3/30 (10%) receiving placebo (Δ=38.3%, 95% CI 17.1-59.4, p=0.002). Adverse events occurred more frequently with mercaptopurine (808.8 per 100 patient years) compared to placebo (501.4 per 100 patient years). Five serious adverse events occurred; four on mercaptopurine and one on placebo. TDM-based dose adjustments were executed in 22/29 (75.9%) patients, leading to lower mercaptopurine doses at week 52 compared to baseline. Optimised mercaptopurine treatment was superior to placebo in achieving clinical, endoscopic and histological outcomes at one year following corticosteroid induction treatment in UC patients. More adverse events occurred in the mercaptopurine group.

Meropenem Model-Informed Precision Dosing in the Treatment of Critically Ill Patients: Can We Use It?

The number of pharmacokinetic (PK) models of meropenem is increasing. However, the daily role of these PK models in the clinic remains unclear, especially for critically ill patients. Therefore, we evaluated the published meropenem models on real-world ICU data to assess their suitability for use in clinical practice. All models were built in NONMEM and evaluated using prediction and simulation-based diagnostics for the ability to predict the subsequent meropenem concentrations without plasma concentrations (a priori), and with plasma concentrations (a posteriori), for use in therapeutic drug monitoring (TDM). Eighteen PopPK models were included for evaluation. The a priori fit of the models, without the use of plasma concentrations, was poor, with a prediction error (PE)% of the interquartile range (IQR) exceeding the ±30% threshold. The fit improved when one to three concentrations were used to improve model predictions for TDM purposes. Two models were in the acceptable range with an IQR PE% within ±30%, when two or three concentrations were used. The role of PK models to determine the starting dose of meropenem in this population seems limited. However, certain models might be suitable for TDM-based dose adjustment using two to three plasma concentrations.

Is there a multinational consensus of tobramycin prescribing and monitoring for cystic fibrosis? Survey of current therapeutic drug monitoring practices in USA/Canada, UK/Ireland, and Australia/New Zealand

ObjectivesSophisticated scientific methods have facilitated dose individualisation with substantial advancements in therapeutic drug monitoring (TDM) practice. It is unclear whether these methods have translated to the clinical setting. This study...

Systematic Comparison of Hospital-Wide Standard and Model-Based Therapeutic Drug Monitoring of Vancomycin in Adults.

We aimed to evaluate the predictive performance and predicted doses of a single-model approach or several multi-model approaches compared with the standard therapeutic drug monitoring (TDM)-based vancomycin dosing. We performed a hospital-wide monocentric retrospective study in adult patients treated with either intermittent or continuous vancomycin infusions. Each patient provided two randomly selected pairs of two consecutive vancomycin concentrations. A web-based precision dosing software, TDMx, was used to evaluate the model-based approaches. In total, 154 patients contributed 308 pairs. With standard TDM-based dosing, only 48.1% (148/308) of all of the second concentrations were within the therapeutic range. Across the model-based approaches we investigated, the mean relative bias and relative root mean square error varied from −5.36% to 3.18% and from 24.8% to 28.1%, respectively. The model averaging approach according to the squared prediction errors showed an acceptable bias and was the most precise. According to this approach, the median (interquartile range) differences between the model-predicted and prescribed doses, expressed as mg every 12 h, were 113 [−69; 427] mg, −70 [−208; 120], mg and 40 [−84; 197] mg in the case of subtherapeutic, supratherapeutic, and therapeutic exposure at the second concentration, respectively. These dose differences, along with poor target attainment, suggest a large window of opportunity for the model-based TDM compared with the standard TDM-based vancomycin dosing. Implementation studies of model-based TDM in routine care are warranted.

Pharmacokinetic analysis of meropenem therapeutic drug monitoring data (TDM) in critically ill adult patients

Meropenem is a carbapenem antibiotic widely used in treatment of severe infections in ICU. Critically ill patients’ pathophysiological features may cause changes in the pharmacokinetics of meropenem, such as augmented/impaired renal clearance, as well as an increase in the volume of distribution of the drug. Considerable variability in meropenem concentration for the same dosage regimen, severity of the diseases and the escalating antibiotic resistance support the need for an individualization of the dosing in critically ill patients. Estimation of meropenem pharmacokinetic (PK) parameters was performed using the NPAG (non-parametric adaptive grid) program from the Pmetrics package based on peak-trough TDM data. A one-compartment linear PK model with zero-order input and first-order elimination was used to analyze data of the 36 critically ill patients (66 measured meropenem concentrations totally) and to predict pharmacodynamic (PD) parameter values (%T&gt;MIC) based on the time course of free meropenem concentration for empirically prescribed dosage regimens by MIC level. The estimated PK parameters of the meropenem model were in good agreement with those published in the literature earlier. A great interindividual variability for PK parameters from 44.5% up to 167% was revealed. Different regression lines between meropenem clearance and clearance creatinine (CLCr) were registered in patients with CLCr [1] 7 L/h versus &gt; 7 L/h: statistically significant regression (n=30, p=0.015) versus no correlation (n=6, р=0.85), respectively. Bayesian feedback TDM-based meropenem dose personalization is the most practical approach to ensure adequate drug exposure in critically ill patients, especially in patients with augmented renal clearance.

Perspectives and Expertise in Establishing a Therapeutic Drug Monitoring Programme for Challenging Childhood Cancer Patient Populations.

The utility of Therapeutic Drug Monitoring (TDM) in the setting of childhood cancer is a largely underused tool, despite the common use of cytotoxic chemotherapeutics. While it is encouraging that modern advances in chemotherapy have transformed outcomes for children diagnosed with cancer, this has come at the cost of an elevated risk of life-changing long-term morbidity and late effects. This concern can limit the intensity at which these drugs are used. Widely used chemotherapeutics exhibit marked inter-patient variability in drug exposures following standard dosing, with fine margins between exposures resulting in toxicity and those resulting in potentially suboptimal efficacy, thereby fulfilling criteria widely accepted as fundamental for TDM approaches. Over the past decade in the UK, the paediatric oncology community has increasingly embraced the potential benefits of utilising TDM for particularly challenging patient groups, including infants, anephric patients and those receiving high dose chemotherapy. This has been driven by a desire from paediatric oncologists to have access to clinical pharmacology information to support dosing decisions being made. This provides the potential to modify doses between treatment cycles based on a comprehensive set of clinical information, with individual patient drug exposures being used alongside clinical response and tolerability data to inform dosing for subsequent cycles. The current article provides an overview of recent experiences of conducting TDM in a childhood cancer setting, from the perspectives of the clinicians, scientists and pharmacists implementing TDM-based dosing recommendations. The ongoing programme of work has facilitated investigations into the validity of current approaches to dosing for some of the most challenging childhood cancer patient groups, with TDM approaches now being expanded from well-established cytotoxic drugs through to newer targeted treatments.

Fluoropyrimidine chemotherapy: recommendations for DPYD genotyping and therapeutic drug monitoring of the Swiss Group of Pharmacogenomics and Personalised Therapy.

Fluoropyrimidines (FPs), mainly 5-fluorouracil (5-FU) and its oral prodrug capecitabine (Cap), remain the backbone of the treatment of many different solid tumors. Despite their broad use in clinical routine, 10&ndash;40% of patients experience severe, and in rare cases (0.2&ndash;0.5%) even lethal, FP-related toxicity in early chemotherapy cycles. Today, there is a plethora of evidence that genetic variants in the gene encoding for the 5-FU catabolising enzyme dihydropyrimidine dehydrogenase (DPD, encoded by DPYD) are predictive of severe FP-related toxicities, and international clinical practice recommendations for DPYD genotype-guided FP dosing and therapeutic drug monitoring (TDM) are available. In spite of this strong evidence and DPYD genotyping becoming standard practice in other countries, it is has not been widely adopted in Switzerland to date. Here, we discuss current guidelines on genotype-guided FP dosing and TDM, and propose recommendations tailored to the situation in Switzerland to facilitate their clinical uptake for the further individualisation of FP chemotherapy. We recommend preemptive testing of four DPYD variants (c.1905+1G&gt;A (rs3918290), c.1679T&gt;G (rs55886062), c.2846A&gt;T (rs67376798) and c.1129-5923C&gt;G (rs75017182, c.1236G&gt;A/HapB3)) in patients with an indication for FP-based chemotherapy, with the costs reimbursed through the compulsory health insurance in Switzerland. Carriers of these variants (6.5% in the Swiss population) have a 40&ndash;50% risk of developing severe early-onset toxicity when treated with standard FP doses. In these patients, we therefore recommend the use of a reduced starting dose, based on a dose adjustment scheme provided herein. Furthermore, we recommend the use of infusional 5-FU in patients with a DPYD risk genotype in order to enable TDM-based dose escalation. Only if the use of an infusional 5-FU regimen is not feasible should a slow titration of Cap, starting with the recommended reduced dose and basing further doses on monitoring of toxicity, be considered. Given that several studies have shown that TDM in 5-FU treatment improves not only the therapy&rsquo;s safety, but potentially also its efficacy, we also include detailed TDM-based dosing guidelines and discuss the pre-analytical aspects of 5-FU TDM.

Busulfan Pharmacokinetics in Adenosine Deaminase-Deficient Severe Combined Immunodeficiency Gene Therapy.

The pharmacokinetics of low-dose busulfan (BU) were investigated as a nonmyeloablative conditioning regimen for autologous gene therapy (GT) in pediatric subjects with adenosine deaminase-deficient severe combined immunodeficiency disease (ADA SCID). In 3 successive clinical trials, which included either γ-retroviral (γ-RV) or lentiviral (LV) vectors, subjects were conditioned with BU using different dosing nomograms. The first cohort received BU doses based on body surface area (BSA), the second cohort received doses based on actual body weight (ABW), and in the third cohort, therapeutic drug monitoring (TDM) was used to target a specific area under the concentration-time curve (AUC). Neither BSA-based nor ABW-based dosing achieved a consistent cumulative BU AUC; in contrast, TDM-based dosing led to more consistent AUC. BU clearance increased as subject age increased from birth to 18 months. However, weight and age alone were insufficient to accurately predict the dose that would consistently achieve a target AUC. Furthermore, various clinical, laboratory, and genetic factors (eg, genotypes for glutathione-S-transferase isozymes known to participate in BU metabolism) were analyzed, but no single finding predicted subjects with rapid versus slow clearance. Analysis of BU AUC and the postengraftment vector copy number (VCN) in granulocytes, a surrogate marker of the level of engrafted gene-modified hematopoietic stem and progenitor cells (HSPCs), demonstrated gene marking at levels sufficient for therapeutic benefit in the subjects who had achieved the target BU AUC. Although many factors determine the ultimate engraftment following GT, this work demonstrates that the BU AUC correlated with the eventual level of engrafted gene-modified HSPCs within a vector group (γ-RV versus LV), with significantly higher levels of granulocyte VCN in the recipients of LV-modified grafts compared to recipients of γ-RV-transduced grafts. Taken together, these findings provide insight into low-dose BU pharmacokinetics in the unique setting of autologous GT for ADA SCID, and these dosing principles may be applied to future GT trials using low-dose BU to open the bone marrow niche.

Intra-individual Pharmacokinetic Variability of Intravenous Busulfan in Hematopoietic Stem Cell-Transplanted Children.

Busulfan therapeutic drug monitoring (TDM) is necessary to better achieve the target exposure in children before hematopoietic stem cell transplantation (HSCT). However, TDM-based dosing may be challenging if intra-individual pharmacokinetic variability (also denoted inter-occasion variability [IOV]) occurs during therapy. The objectives of this study were to describe and quantify busulfan IOV in children, and to investigate its potential determinants. We performed a new analysis of published data from children who received intravenous busulfan over 4days before HSCT. We calculated individual pharmacokinetic parameters on each day of therapy using a published population pharmacokinetic model of busulfan and analyzed their changes. Population estimation of IOV was also performed with non-linear mixed effects (NLME) modeling. Potential predictors of significant decrease in busulfan clearance (CL) were assessed by using machine learning approaches. IOV could be assessed in 136 children. Between day (D)1 and D2, most patients (80%) experienced a decrease in busulfan CL, with a median change of - 7.9%. However, both large decreases (minimum, - 48.5%) and increases in CL (maximum, + 44%) were observed. Over D1-D3 of therapy, mean CL significantly decreased (- 15%), with a decrease of ≥ 20% in 22% of patients. Some patients also showed unstable CL from day to day. NLME modeling of IOV provided a coefficient of variation of 10.6% and 13.1% for volume of distribution (Vd) and CL, respectively. Some determinants of significant decreases in busulfan CL were identified, but predictive performance of the models was limited. Significant busulfan intra-individual variability may occur in children who receive a HSCT and is hardly predictable. The main risk is busulfan overexposure. Performing TDM repeatedly over therapy appears to be the best way to accurately estimate busulfan exposure and perform precision dosing.

Single Arm, Single Centre Prospective Study to Assess the Effect of Therapeutic Drug Monitoring (TDM) Based Dosage Adjustment of Posaconazole on the Incidence of Invasive Fungal Infections (IFIs) in AML Patients on Induction Chemotherapy on Posaconazole Prophylaxis

Background: Invasive fungal infections (IFIs) continue to remain a significant cause of morbidity and mortality in AML patients affecting the final outcomes and increasing health care costs. Posaconazole is commonly used as prophylaxis against IFIs due to its broad spectrum of action. The incidence of breakthrough IFIs is particularly high in our setting - one of the several reasons being suboptimal drug levels as we use posaconazole suspension whose absorption is influenced by multiple factors. A breakthrough IFI rate of 51% was seen in a previous study from our centre by Sengar et.al (ASH 2016) and it was seen that sub-optimal drug levels (&lt; 700ng/ml) were associated with a higher rate of breakthrough IFI. This group can benefit from TDM but there are not many studies to guide TDM-based dosing of posaconazole. TDM is expensive and time consuming and the final impact on clinical outcomes has been difficult to estimate. To determine the impact of TDM-based dosing of posaconazole on breakthrough IFI rate, we have undertaken this prospective study. Methods: This prospective, single-arm interventional study included patients 16 years or older undergoing induction chemotherapy for de novo AML with no evidence of IFI at baseline (normal CT chest and normal serum galactomannan ) who have consented for participation (assent and guardian consent were used for those who were &lt; 18 years). Concomitant drugs during induction were recorded everyday. 3 dosing schedules for posaconazole were used based on the drug level : Level 1 - 200mg TDS which was the starting dose in all patients, Level 2 - 200mg QID and Level 3 - 400mg TDS which was the maximum dose. Posaconazole was given with a high fat meal or an aerated drink to improve its absorption. The cut off for day 2 drug level (i.e after atleast 3-4 doses ) was 350ng/ml and the cut-off level at subsequent time points was 700 ng/ml. At any time point, if the patient's drug level was below this cut off, the dose was escalated and a repeat level was sent 5 complete days after the changed dose to allow for re-establishment of the pharmacokinetic equilibrium. A day 2 level was sent for all the patients and the timing of subsequent levels was based on dose escalation. Patients who were continued on the same dose due to adequate drug levels were sampled once in 7 days. QTc interval and liver function tests were monitored for posaconazole toxicity. Posaconazole was continued till the absolute neutrophil count recovered to more than 500 cells/ µl or till the patient was started on an alternative anti-fungal for a proven , possible or probable IFI or empirically at the clinician's discretion for reasons like persistent fever, cough, breathlessness, diarrhoea or vomiting. Relevant imaging and microbiological tests were performed as needed for investigating a suspected IFI. To analyze the primary endpoint chi-square test was used to compare the breakthrough IFI rate with that in a historical cohort from our own centre in which TDM based dosing was not used. Results: A total of 278 samples were collected for drug levels in these 90 patients with a mean of 3.08 (range 1 to 6 samples) per patient . 2 patients were proven to have mixed phenotypic acute leukemia after enrollment and hence were excluded from the analysis. 46 out of 88 patients i.e 52.3% were changed to alternative antifungals. Out of these 46, 13 patients (i.e 28.3%) had proven, probable or possible IFI as per the Revised Definitions of Invasive Fungal Disease from the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) . The change to alternative antifungals in the remaining 33 out of 46 patients (i.e 71.7%) was empirical due to persistent fever spikes, vomiting or diarrhoea. Thus overall 13 out of 88 patients i.e 14.8% had developed a breakthrough IFI. A similar historical cohort from our own institute, without the TDM based dosing of posaconazole, had a breakthrough IFI rate of 52%. The difference between the breakthrough IFI rate of these 2 cohorts was 37.2% which was statistically significant (p &lt; 0.0001, 95% CI 27.9% to 52.4%). 1 patient had developed grade 3 transaminitis and 1 patient had grade 3 rise in total bilirubin while on posaconazole. Conclusion: TDM-based dose escalation of prophylactic posaconazole in AML patients during induction leads to a significant reduction in the breakthrough IFI rates. Disclosures No relevant conflicts of interest to declare.

Impact of dose adaptations following voriconazole therapeutic drug monitoring in pediatric patients.

Voriconazole is the mainstay of treatment for invasive aspergillosis in immunocompromised pediatric patients. Although Therapeutic Drug Monitoring (TDM) of voriconazole is recommended, it remains unknown if TDM-based dose adaptations result in target attainment. Patients <19 years from two pediatric hematologic-oncology wards were retrospectively identified based on unexplained high voriconazole trough concentrations (Cmin >6mg/l). Patient demographics, clinical characteristics, treatment, voriconazole dosing information, voriconazole Cmin before and after adjustment based on TDM were obtained. Twenty-one patients, median (range) age 7.0 (1.2-18.5) years, were identified in two centers. First Cmin (3.1mg/l [0.1-13.5]) was obtained after 3 days (1-27) of treatment. The median of all Cmin (n = 485, median 11 per patient) was 2.16mg/l (0.0 (undetectable)-28.0), with 24.1% of Cmin < 1mg/l, 48.9% 1-4mg/l, 9.3% 4-6mg/l, and 17.7% >6mg/l. Intrapatient variability was large (94.1% for IV, 88.5% for PO). Dose increases at Cmin < 1mg/l resulted in an increased Cmin in 76.4%, with 60% between 1 and 4mg/l. Dose decreases at Cmin >6mg/l resulted in a decreased Cmin in 80%, with 51% between 1 and 4mg/l. Overall, in 45% of the cases (33 out of 55 and 12 out of 45) therapeutic targets were attained after dose adjustment. Fifty-five percent of initial Cmin was outside the therapeutic target of 1-4mg/l, with multiple dose adaptations required to achieve therapeutic concentrations. Only 60% and 51% of dose adaptations following sub- and supra-therapeutic Cmin, respectively, did result in target attainment. Intensive and continuous TDM of voriconazole is a prerequisite for ensuring adequate exposure in pediatric patients.

Optimising infliximab induction dosing for patients with ulcerative colitis.

The therapeutic failure of infliximab therapy in patients with ulcerative colitis remains a challenge even 2 decades after its approval. Therapeutic drug monitoring (TDM) has shown value during maintenance therapy, but induction therapy has still not been explored. Patients may be primary nonresponders or underexposed with the standard dosing regimen. We aimed to: (i) develop a population pharmacokinetic-pharmacodynamic model; (ii) identify the best exposure metric that predicts mucosal healing; and (iii) build an exposure-response (ER) model to demonstrate model-based dose finding during induction therapy with infliximab. Data were retrospectively collected from a clinical database. A total of 583 samples, from 204 patients, was used to develop a population pharmacokinetic model to generate exposure metrics for subsequent ER modelling. A subset of 159 patients was used to develop a logistic regression ER model, describing the relationship between infliximab exposure and ordered transitions between Mayo endoscopic subscore (MES) 3, 2 and ≤1 (baseline to post-induction). A 1-compartment population pharmacokinetic model with interindividual and interoccasion variability was found to fit the data best. Covariates influencing exposure were C-reactive protein, albumin, baseline MES, fat-free mass, concomitant corticosteroid use and pancolitis. The cumulative area under the infliximab concentration-time curve until endoscopy (CAUCendoscopy ) was found to be the best exposure metric for predicting mucosal healing (baseline MES >1 and post-induction MES ≤1). The model predicted that 70% of patients will attain mucosal healing with infliximab administered at days 0, 14 and 42 and a target CAUCendoscopy of 3752mg/L*day at day 84. TDM-based dose individualisation targeting CAUCendoscopy has the potential to improve the effectiveness of infliximab during induction therapy.

Interest of therapeutic drug monitoring of aminoglycosides administered by a monodose regimen

BackgroundAlthough the once-daily regimen of aminoglycosides (AG) is considered as predominantly used by many centers, the level of evidence of Therapeutic Drug Monitoring (TDM) of AG in cases of once-daily has not been clearly defined. The objective of this study is to evaluate the impact of TDM in achievement or maintaining target serum concentrations in patients receiving once-daily administration of AG. MethodsWe performed a retrospective analysis of data from patients having received a once daily amikacin or gentamicin and underwent routine TDM. A longitudinal follow up was performed. Data were analyzed according to the adhesion or not to recommendations. A logistic regression was performed in order to evaluate the effect of covariates (age, gender, weight, creatinine clearance [CLcr], TDM-based dose adjustment, weighted dose of AG) on the achievement of non-toxic Cmin. ResultsA total 437 blood samples issued from 324 patients were analyzed. The cut-off value of Clcr associated with a risk of toxic Cmin was≤41.66mL/min (OR: 11.29; 95%CI: 7.21–17.61; P<0.0001). Eighty-eight patients (27.1%) have at least two sampling points. The univariate analysis showed that the age, weight, CLcr and TDM-based dose adjustment were found to be significant factors in the achievement of non-toxic Cmin. In multivariate analysis, only TDM-based dose adjustment remains a significant factor in the achievement of non-toxic Cmin (OR: 6.66; 95%CI: 2.26–19.63; P=0.0006). ConclusionOur study demonstrates the usefulness of TDM-based dosing adjustment of AG antibiotics in achieving nontoxic trough concentrations, particularly in critically ill patients, as they are prone to a renal impairment.

Comparison of three estimators for determining cyclosporine dosing in infants after liver transplantation .

To compare and analyze how allometrically- and linearly-scaled daily doses of cyclosporine could affect the therapeutic drug monitoring concentrations when applied to 8 infants with liver transplants. Eight infants who underwent liver transplantations were put on twice-daily oral cyclosporine immunosuppressive regimens. After starting therapy, the adjustments of individual daily doses were determined by using therapeutic monitoring of plasma cyclosporine levels by measuring trough concentrations (C₀) and concentrations at 2 hours after drug administration (C₂). These doses were analyzed and compared with the hypothetical doses estimated by allometric and linear scaling in order to compare which of the two methods would yield closer estimates to the actual doses applied. The median therapeutic drug monitoring (TDM)-based dose (n=53) was 70.00 mg (10.9 mg/kg/day) (5.00-190.00 mg), whereas the median allometric (n=53) and linear (n=53) doses were 65.21 mg (10.11 mg/kg/day) (57.17-79.25 mg) and 35.63 mg (5.52 mg/kg/day) (29.89-46.20 mg), respectively. The median allometric dose was significantly different than the median linear dose (p<0.0001), whereas there was no statistical difference between the median TDM-based dose and median allometric dose (p=0.72). The allometric approach, when used to estimate cyclosporine doses in this cohort of liver transplant infants, yielded closer estimates to actually applied daily doses in comparison to linear scaling. Allometric scaling could be employed in calculating starting doses for drugs that lack specific dosing recommendations for infants, in order to achieve therapeutic levels faster, lowering the need for constant monitoring and dose adjustment. .

Quality Assessment for Therapeutic Drug Monitoring in AIDS Clinical Trials Group (ACTG 5146): A Multicenter Clinical Trial

In a randomized trial, AIDS Clinical Trials Group (ACTG) protocol 5146 (A5146) investigated the use of therapeutic drug monitoring (TDM) to adjust doses of HIV-1 protease inhibitors (PIs) in patients with prior virologic failure on PI-based therapy who were starting a new PI-based regimen. The overall percentage of "PI trough repeats" such as rescheduled visits or redrawn PI trough specimens increased from 2% to 5% to 10% as the process progressed from the clinical sites, the pharmacology specialty laboratory, and the study team, respectively. Cumulatively, this represents a 17% rate of failure to obtain adequate PI trough sample. While targeting a turnaround of 7 days or less from sample receipt to a drug concentration report, 12% of the received specimens required a longer period to report concentrations. The implementation of dosing changes in the TDM arm were achieved within 7 days or less for 56% of the dose change events and within 14 days or less for 77% of dose change events. This quality assurance analysis provides a valuable summary of the specific points in the TDM process that could be improved during a multicenter clinical trial including: 1) shortening the timeline of sample shipment from clinical site to the laboratory; 2) performing the collection of PI trough specimen within the targeted sampling window by careful monitoring of the last dose times and collection times by the clinicians; 3) increasing patient adherence counseling to reduce the number of samples that are redrawn due to suspecting inconsistent adherence; and 4) decreasing the time to successful TDM-based dose adjustment. The application of some of these findings may also be relevant to single-center studies or clinical TDM programs within a hospital.