Conventional Weight-based Dosing Research Articles

Comparison of Hemodynamic Effects of Dose Response vs. Conventional Dosing of Propofol for Anesthesia Induction Under Bispectral Index Monitoring: A Clinical Trial

Propofol is an advantageous agent for anesthesia induction. It can cause dose-related hemodynamic adverse effects. The bispectral index (BIS) is a brain function monitor utilized to assess the depth of anesthesia. This study aimed to compare the adverse hemodynamic effects of BIS-guided response dosing with conventional weight-based dosing of Propofol. In this clinical trial, patients were anesthetized with propofol in two different orthopedic operating rooms. In one operating room, patients received propofol with dose-response method (group A), and the other received weight-based dosing (group B). For both groups, BIS was used as an index of anesthesia depth. Hemodynamic parameters were recorded at baseline, during induction, and at different time points. A total of 73 patients were included in the final analysis. The mean dose of propofol for induction was higher in the control group than in the response-guided group (1.94±1.65 vs. 1.09±0.32, respectively, P=0.006). There were no reported significant adverse hemodynamic effects in patients of the two groups. Response-guided propofol dosing can be used to decrease propofol dose during anesthesia induction. Further studies are needed to investigate the clinical benefit of this dosing strategy.

Comparison of Blood Concentration and Weight-Based Heparin and Protamine Dosing Strategies for Cardiopulmonary Bypass: A Systematic Review and Meta-Analysis.

The conventional method of heparin and protamine management during cardiopulmonary bypass (CPB) is based on total body weightwhich fails to account for the heterogeneous response to heparinin each patient. On the other hand, the literature is inconclusive on whether individualized anticoagulation management based on real-time blood heparin concentration improves post-CBP outcomes. We searched databases of Medline, Excerpta Medica dataBASE (EMBASE), PubMed, Cumulative Index to Nursing and Allied Health Literature (CINHL), and Google Scholar, recruiting randomized controlled trials (RCTs) and prospective studies comparing the outcomes of dosing heparinand/or protamine based on measured heparin concentration versus patient'stotal body weightfor CPB.Random effects meta-analyses and meta-regression were conducted to compare the outcome profiles. Primary endpoints include postoperative blood loss and the correlation with heparin and protamine doses, the reversal protamine and loading heparin dose ratio; secondary endpoints included postoperative platelet counts, antithrombin III, fibrinogen levels, activated prothrombin time (aPTT), incidences of heparin rebound, and re-exploration of chest wound for bleeding. Twenty-six studies, including 22 RCTs and four prospective cohort studies involving 3,810 patients, were included.Compared to body weight-based dosing, patients of individualized, heparin concentration-based group had significantly lower postoperative blood loss (mean difference (MD)=49.51mL, 95% confidence interval (CI): 5.33-93.71), lower protamine-to-heparin dosing ratio (MD=-0.20, 95% CI: -0.32~ -0.12), and higher early postoperative platelet counts (MD=8.83, 95% CI: 2.07-15.59). The total heparin doses and protamine reversal were identified as predictors of postoperative blood loss by meta-regression. There was a significant correlation between the doses of heparin and protamine with postoperative blood loss; therefore, précised dosing of both could be critical for reducingbleeding and transfusion requirements. Data from the enrolled studies indicated that compared to conventional weight-based dosing, individualized, blood concentration-based heparin and protamine dosing may have outcome benefits reducing postoperative blood loss.The dosing calculation of heparin based on the assumption of a one-compartment pharmacokinetic/pharmacodynamic (PK/PD) model and linear relationship between the calculated dose and blood heparin concentration may be inaccurate.With the recent advancement of the technologies of machine learning, individualized, precision management of anticoagulation for CPB may be possible in the near future.

95 Baseline body-mass-index and risk for obesity in children with rheumatic disease starting high-dose prednisone therapy

Abstract Primary Subject area Rheumatology Background Prednisone is a glucocorticoid (GC) medication commonly used in moderate (>7.5 mg/day) to high doses (≥ 1 mg/kg/day to maximum 60 mg/day) for children with moderate to severe presentations of rheumatic disease, including systemic lupus erythematosus (SLE), juvenile idiopathic arthritis (JIA), and juvenile dermatomyositis (JDM). Adverse effects (AE) to GCs impose a significant burden on health and quality of life including frequent development of weight gain, mood changes, sleep difficulties, osteoporosis, and Cushingoid features, amongst others. Objectives We sought to evaluate a possible relationship between baseline patient body-mass-index (BMI) measure and development of select GC-mediated toxicity within the first 12 months of starting moderate or high-dose prednisone therapy using conventional weight-based dosing of prednisone. Secondary outcomes were to examine rates of GC-mediated hypertension, osteopenia, and osteoporosis. Design/Methods We performed a retrospective chart review on children with rheumatic disease aged ≤ 17 years treated with moderate and high-dose prednisone therapy at a single Canadian academic hospital between January 1, 2010 and December 31, 2019. Demographic variables collected included diagnosis, age, sex, ethnicity. Clinical variables collected include weight, height, and body-mass-index (BMI), hepatitis (AST>41 U/L, ALT>40 U/L, or GGT>60 U/L), proteinuria (>0.1 g/L), and presence of hypoalbuminemia (<38g/L) at baseline. We collected weight, height, and body-mass-index (BMI), at 6 and 12 months, the maximum BMI, and transformed them to z-scores according to the World Health Organization's Child Growth standards. Cumulative prednisone dose (mg/kg/12 months), total days on prednisone in the first 12 months of therapy were also obtained, in addition to bone-mineral-density cores after 12 months of prednisone therapy. Baseline characteristics, which were significant for the subsequent development of obesity during the first 12 months at the bivariate level (p < 0 .05), were included as predictors of obesity in separate logistic regression analyses. In each regression analysis, we also adjusted for baseline BMI, and for confounding variables of hepatitis, hypoalbuminemia (albumin less than 38 grams per litre), proteinuria and prednisone dose. We conducted a complete case analysis, and all analyses were performed using SPSS v.26 (IBM Corp., Armonk, NY, USA), and p-values < 0 .05 were considered statistically significant. Results Seventy-four charts were reviewed, and 72 patients met criteria for analysis. The median prednisone dose was 35 mg per day (IQR 20 to 60 mg), and median duration of therapy was 302 days (IQR 126.75 to 581.25). Thirty-five (48.6%) patients developed obesity, 33 (45.8%) hypertension, five (7.0%) osteopenia, and three (4.2%) osteoporosis. Greater BMI at baseline was associated with greater total weight gain (OR 4.04, 95% CI = [1.98-8.33], p < 0 .001). Conclusion Greater baseline patient BMI may be a predictor of weight gain on high-dose prednisone therapy in children with rheumatic disease requiring high-dose therapy. Further work is required to determine methods for individualized prednisone dosing and counseling and behavioral interventions to mitigate risk for weight gain.

Real-World Use of Azathioprine Metabolites Changes Clinical Management of Inflammatory Bowel Disease

BackgroundThiopurines such as 6-mercaptopurine and azathioprine have complex metabolism, resulting in significant inter-individual differences in clinical efficacy and risk of drug toxicity, making conventional weight-based dosing inaccurate and potentially unsafe. Therapeutic drug monitoring (TDM) of thiopurine metabolites improves clinical outcomes through dose optimization and toxicity monitoring. Despite evidence for TDM, use is limited, due in part to test availability and awareness. The objectives of this study were twofold: (1) to investigate how thiopurine TDM impacts clinical management of IBD patients and (2) to evaluate proportion of patients outside therapeutic 6TGN levels or exhibiting signs of toxicityMethodsPatients who received thiopurine TDM as part of routine care underwent chart review of demographics, disease activity, medication dosing, metabolite levels, and adverse events. Changes in clinical management following TDM were measured. Additionally, we conducted a retrospective review of clinical decision making blinded and unblinded to TDM result.ResultsA total of 92 IBD patients were included. Levels of 6TGN were therapeutic in 29% of patients. 6TGN levels correlated weakly with weight-based dosing (r2 = 0.057, P = 0.02). Adverse reactions were observed in 6.5%. TDM informed clinical management in 64%. Significantly more changes to clinical management occurred in those with active disease than in remission (73% versus 48%; P = 0.02) and in those on mono- versus combination therapy (48% versus 27.5%; P = 0.03).ConclusionsTDM informs clinical decision making in over two-thirds of patients. The demonstrated poor efficacy of weight-based dosing and impact of TDM on clinical management contributes to the evidence supporting the need for greater availability and uptake of thiopurine TDM.

Hydroxyurea Pharmacokinetic Profiles in Children Treated for Extreme Thrombocytosis after Total Pancreatectomy with Islet Cell Autotransplant Demonstrate Poor Absorption

Background Total pancreatectomy with islet autotransplantation (TPIAT) is a surgical treatment for chronic recurrent pancreatitis that involves splenectomy, pancreatectomy and creation of a Roux-en-Y, followed by re-injection of the pancreatic islets into the portal vein. Postoperatively, patients develop a sustained and extreme thrombocytosis (ExT) with platelets ≥1000 K/μL, a response more exaggerated than the typical post-splenectomy course (Gurria JP et al, Pancreas 2019). Empiric aspirin (antiplatelet effect) and hydroxyurea (cytoreduction) are initiated postoperatively per a standard protocol. The pharmacokinetic (PK) and pharmacodynamic (PD) profiles of hydroxyurea have not been studied in children other than young children with sickle cell disease; neither dose nor dose interval have been evaluated in TPIAT patients. Recently a population PK model was developed to support individualized hydroxyurea dosing in patients with sickle cell anemia (SCA; Dong M et al, Br J Clin Pharmacol 2016). In a prospective evaluation as part of the Therapeutic Response Evaluation and Adherence Trial (TREAT, McGann PT et al, Am J Hematol 2019), PK-guided individualized dosing resulted in better clinical and laboratory benefits than with conventional weight-based dosing. This study aimed to determine if a hydroxyurea PK model could be developed for non-SCA children dosed postoperatively for control of TPIAT-associated ExT, and if so, to compare it to previously published models for SCA. Methods A prospective single-site pilot study was performed in patients ages 0-21 years who underwent TPIAT between April 2018 and June 2019. Whole blood was collected via finger stick or venipuncture at 3 time points (20 minutes, 1 hour, 4 hours) after the initial hydroxyurea dose (15-20 mg/kg), given between postoperative day 5-7 (PK1). Plasma hydroxyurea was quantified by high performance liquid chromatography on 150-200 μL plasma. Testing was repeated once 2-6 months postoperatively (PK2) to determine whether PK profiles changed over time in relation to surgery. PK analyses and estimation of the area under the concentration-time curve (AUC) as a measure of exposure were performed using MW/Pharm (Mediware, Prague, Czech Republic). PK data from HUSTLE (NCT00305175) were used for comparison to SCA patients. Results Of 19 enrolled subjects, 15 had evaluable results: 7 had both PK collections while 8 had a single collection (5 only had PK1, 3 only had PK2). All 5 patients with only PK1 measurements had discontinued hydroxyurea by the time PK2 samples would have been collected, whereas those with only PK2 all had unsuccessful PK1 collection attempts. Mean age was 13.5 years [standard deviation (SD) 5] with mean weight-based dose 14 mg/kg (SD 3.4). Serum creatinine was normal for age in all patients. Hydroxyurea suspension was delivered via jejunal tube at PK1 while oral tablets were used at PK2 per surgical protocol. The AUC was 60.1 h*μg/ml at PK1 and 68.6 h*μg/ml at PK2. When compared to HUSTLE cohort (Figure 1), TPIAT subjects overall had lower drug exposure (AUC), worse for PK1 than PK2, especially when hydroxyurea concentration was normalized to dose. TPIAT patients also appear to have had slower absorption, evidenced by still-rising hydroxyurea concentrations after 1 hour, compared to 20-30 minute peak concentrations in HUSTLE. Conclusions TPIAT subjects treated empirically with hydroxyurea to modulate ExT have decreased absorption and overall lower concentrations and drug exposure relative to our SCA population. Lower bioavailability and/or altered absorption may in part be caused by differences in formulation (suspension versus tablet) and route of administration (oral versus jejunal) along with postoperative anatomic changes not present in the SCA cohort, since Roux-en-Y may alter drug absorption and metabolism (Rogers CC et al, Clin Transpl2008). It is unknown whether higher enteral hydroxyurea doses would increase exposure and effect. Additional evaluation of the absorption characteristics and PK/PD of hydroxyurea in TPIAT patients, as well as efficacy, are urgently needed. Figure 1 Disclosures Ware: Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Nova Laboratories: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: DSMB; Bristol Myers Squibb: Other: Research Drug Donation; Addmedica: Other: Research Drug Donation. OffLabel Disclosure: Hydroxyurea to reduce extreme thrombocytosis after splenectomy/pancreatic islet cell transplant in children

Personalised Warfarin Dosing in Children Post-cardiac Surgery

Warfarin dosing is challenging due to a multitude of factors affecting its pharmacokinetics (PK) and pharmacodynamics (PD). A novel personalised dosing algorithm predicated on a warfarin PK/PD model and incorporating CYP2C9 and VKORC1 genotype information has been developed for children. The present prospective, observational study aimed to compare the model with conventional weight-based dosing. The study involved two groups of children post-cardiac surgery: Group 1 were warfarin naïve, in whom loading and maintenance doses were estimated using the model over a 6-month duration and compared to historical case-matched controls. Group 2 were already established on maintenance therapy and randomised into a crossover study comparing the model with conventional maintenance dosing, over a 12-month period. Five patients enrolled in Group 1. Compared to the control group, the median time to achieve the first therapeutic INR was longer (5 vs. 2 days), to stable anticoagulation was shorter (29.0 vs. 96.5 days), to over-anticoagulation was longer (15.0 vs. 4.0 days). In addition, median percentage of INRs within the target range (%ITR) and percentage of time in therapeutic range (%TTR) was higher; 70% versus 47.4% and 83.4% versus 62.3%, respectively. Group 2 included 26 patients. No significant differences in INR control were found between model and conventional dosing phases; mean %ITR was 68.82% versus 67.9% (p = 0.84) and mean %TTR was 85.47% versus 80.2% (p = 0.09), respectively. The results suggest model-based dosing can improve anticoagulation control, particularly when initiating and stabilising warfarin dosing. Larger studies are needed to confirm these findings.

Modeling the Outcome of Systematic TPMT Genotyping or Phenotyping Before Azathioprine Prescription: A Cost-Effectiveness Analysis.

Thiopurine S-methyltransferase (TPMT) testing, either by genotyping or phenotyping, can reduce the incidence of adverse severe myelotoxicity episodes induced by azathioprine. The comparative cost-effectiveness of TPMT genotyping and phenotyping are not known. Our aim was to assess the cost-effectiveness of phenotyping-based dosing of TPMT activity, genotyping-based screening and no screening (reference) for patients treated with azathioprine. A decision tree was built to compare the conventional weight-based dosing strategy with phenotyping and with genotyping using a micro-simulation model of patients with inflammatory bowel disease from the perspective of the French health care system. The time horizon was set up as 1year. Only direct medical costs were used. Data used were obtained from previous reports, except for screening test and admission costs, which were from real cases. The main outcome was the cost-effectiveness ratios, with an effectiveness criterion of one averted severe myelotoxicity episode. The total expected cost of the no screening strategy was €409/patient, the total expected cost of the phenotyping strategy was €427/patient, and the total expected cost of the genotyping strategy was €476/patient. The incremental cost-effectiveness ratio was €2602/severe myelotoxicity averted in using the phenotyping strategy, and €11,244/severe myelotoxicity averted in the genotyping strategy compared to the no screening strategy. At prevalence rates of severe myelotoxicity > 1%, phenotyping dominated genotyping and conventional strategies. The phenotype-based strategy to screen for TPMT deficiency dominates (cheaper and more effective) the genotype-based screening strategy in France. Phenotype-based screening dominates no screening in populations with a prevalence of severe myelosuppression due to azathioprine of > 1%.

Prevalence and impact of obesity in people with haemophilia: Review of literature and expert discussion around implementing weight management guidelines.

Obesity affects more than 35% of Americans, increasing the risk of more than 200 comorbid conditions, impaired quality of life and premature mortality. This review aimed to summarize literature published over the past 15years regarding the prevalence and impact of obesity in people with haemophilia (PWH) and to discuss implementing general guidelines for weight management in the context of the haemophilia comprehensive care team. Although few studies have assessed the effects of obesity on haemophilia-specific outcomes, existing evidence indicates an important impact of weight status on lower extremity joint range of motion and functional disability, with potentially important effects on overall quality of life. Data regarding bleeding tendency in PWH with coexisting obesity are largely inconclusive; however, some individuals may experience reduced joint bleeds following moderate weight loss. Additionally, conventional weight-based dosing of factor replacement therapy leads to increased treatment costs for PWH with obesity or overweight, suggesting pharmacoeconomic benefits of weight loss. Evidence-based recommendations for weight loss include behavioural strategies to reduce caloric intake and increase physical activity, pharmacotherapy and surgical therapy in appropriate patients. Unique considerations in PWH include bleed-related risks with physical activity; thus, healthcare professionals should advise patients on types and intensities of, and approaches to, physical activity, how to adjust treatment to accommodate exercise and how to manage potential activity-related bleeding. Increasing awareness of these issues may improve identification of PWH with coexisting obesity and referral to appropriate specialists, with potentially wide-ranging benefits in overall health and well-being.

Weight and Body Composition Compartments do Not Predict Therapeutic Thiopurine Metabolite Levels in Inflammatory Bowel Disease.

OBJECTIVES:Thiopurine drugs are the most commonly used steroid-sparing therapies in moderate-to-severe inflammatory bowel disease (IBD). Their complex metabolism and their narrow therapeutic windows means that optimal dosing is difficult. However, weight-based dosing is the norm. Similar antimetabolites are dosed by body composition parameters. In IBD, treatment response and toxicity has been shown to correlate with thiopurine metabolite levels. We sought to determine whether weight or body composition parameters predicted therapeutic 6-thioguanine nucleotide (6TGN) or toxic 6-methylmercaptopurine (6MMP) levels.METHODS:This single-center retrospective cohort study identified 66 IBD patients who had body composition analysis and thiopurine metabolite levels tested. Statistical analysis was performed using Spearman correlation, Kruskal–Wallis, Mann–Whitney, and unpaired t tests and receiver-operator operating characteristic curves. A P value of <0.05 was considered significant.RESULTS:No correlation was identified between 6TGN and any body composition parameters, absolute drug dose or drug dose/kg of fat mass, fat-free mass (FFM), subcutaneous adipose tissue area, or visceral adipose tissue area. However, 6MMP correlated with azathioprine dose, thiopurine dose/kg of body weight, and with several body composition parameters.CONCLUSIONS:No relationship was found between therapeutic metabolite levels and weight or body composition compartments. Higher thiopurine doses, especially in relation to FFM, are associated with higher levels of potentially hepatotoxic 6MMP and shunting toward this metabolite. Conventional weight-based dosing to attain therapeutic metabolite levels appears unreliable and may be replaced by metabolite level testing.

Review article: applying pharmacokinetics to optimise dosing of anti-TNF biologics in acute severe ulcerative colitis.

Acute severe ulcerative colitis (ASUC), the most aggressive presentation of ulcerative colitis (UC), occurs in 15% of adults and children with UC. First line therapy with intravenous corticosteroids is ineffective in half of adults and one-third of children. Therapeutic monoclonal antibodies against TNF (anti-TNF therapy) are emerging as a common treatment for ASUC due to their similar efficacy to calcineurin inhibitors and more favourable adverse effect profile. To comprehensively review the evidence for anti-TNF therapy for ASUC in children and adults with regard to outcomes and pharmacokinetics. PubMed and recent conference proceedings were searched using the terms 'ulcerative colitis', 'acute severe ulcerative colitis', 'anti-TNF', 'pharmacokinetics' and the generic names of specific anti-TNF agents. Outcomes after anti-TNF therapy for ASUC remain suboptimal with about one half of children and adults undergoing colectomy. While several randomised controlled trials have demonstrated the efficacy of anti-TNF therapy for ambulatory patients with moderate to severely active UC, patients in these studies were less ill than those with ASUC. Patients with ASUC may exhibit more rapid clearance of anti-TNF biologics due to pharmacokinetic mechanisms influenced by disease severity. Conventional weight-based dosing effective in patients with moderately to severely active UC, may not be equally effective in those with acute severe ulcerative colitis. Personalised anti-TNF dosing strategies, which integrate patient factors and early measures of pharmacokinetics and response, hold promise for ensuring sustained drug exposure and maximising early mucosal healing in patients with acute severe ulcerative colitis.

The role of thiopurine metabolites in inflammatory bowel disease and rheumatological disorders

Thiopurines have been a cornerstone of medical management of patients with inflammatory bowel disease(IBD) and many rheumatological disorders. The thiopurines are metabolized to their end products, 6-methymercaptopurine (6MMP) and the 6-thioguanine nucleotides (6TGN), with 6TGN being responsible for thiopurine efficacy by causing apoptosis and preventing activation and proliferation of T-lymphocytes. In IBD, conventional weight-based dosing with thiopurines leads to an inadequate response in many patients. Utilizing measurement of these metabolites and then employing dose optimization strategies has led to markedly improved outcomes in IBD. Switching between thiopurines as well as the addition of low-dose allopurinol can overcome adverse events and elevate 6TGN levels into the therapeutic window. There is a paucity of data on thiopurine metabolites in rheumatological diseases and further research is required.