Population pharmacokinetic and pharmacokinetic-pharmacodynamic modeling of bempedoic acid and low-density lipoprotein cholesterol in healthy subjects and patients with dyslipidemia

Population pharmacokinetics (popPK) of bempedoic acid and the popPK/pharmacodynamic (popPK/PD) relationship between bempedoic acid concentrations and serum low-density lipoprotein cholesterol (LDL-C) from baseline were characterized. A two-compartment disposition model with a transit absorption compartment and linear elimination best described bempedoic acid oral pharmacokinetics (PK). Multiple covariates, including renal function, sex, and weight, had statistically significant effects on the predicted steady-state area under the curve. Mild (estimated glomerular filtration rate (eGFR) 60 to < 90 mL/min vs. ≥ 90 mL/min) and moderate (eGFR 30 to < 60 mL/min vs. ≥ 90 mL/min) renal impairment, female sex, low (< 70 kg vs. 70-100 kg) and high (> 100 kg vs. 70-100 kg) body weight were predicted to have a 1.36-fold (90% confidence interval (CI) 1.32, 1.41), 1.85-fold (90% CI 1.74, 2.00), 1.39-fold (90% CI 1.34, 1.47), 1.35-fold (90% CI 1.30, 1.41), and 0.75-fold (90% CI 0.72, 0.79) exposure difference relative to their reference populations, respectively. An indirect response model described changes in serum LDL-C with a model-predicted 35% maximal reduction and bempedoic acid IC50 of 3.17 µg/mL. A 28% reduction from LDL-C baseline was predicted for a steady-state average concentration of 12.5 µg/mL after bempedoic acid (180 mg/day) dosing, accounting for approximately 80% of the predicted maximal LDL-C reduction. Concurrent statin therapy, regardless of intensity, reduced the maximal effect of bempedoic acid but resulted in similar steady-state LDL-C levels. While multiple covariates had statistically significant effects on PK and LDL-C lowering, none were predicted to warrant bempedoic acid dose adjustment.

Pharmacodynamic effect of bempedoic acid and statin combinations: predictions from a dose-response model

AIMS

Many patients are unable to achieve guideline-recommended LDL cholesterol (LDL-C) targets, despite taking maximally tolerated lipid-lowering therapy. Bempedoic acid, a competitive inhibitor of ATP citrate lyase, significantly lowers LDL-C with or without background statin therapy in diverse populations. Because pharmacodynamic interaction between statins and bempedoic acid is complex, a dose-response model was developed to predict LDL-C pharmacodynamics following administration of statins combined with bempedoic acid.

METHODS AND RESULTS

Bempedoic acid and statin dosing and LDL-C data were pooled from 14 phase 1-3 clinical studies. Dose-response models were developed for bempedoic acid monotherapy and bempedoic acid-statin combinations using previously published statin parameters. Simulations were performed using these models to predict change in LDL-C levels following treatment with bempedoic acid combined with clinically relevant doses of atorvastatin, rosuvastatin, simvastatin, and pravastatin. Dose-response models predicted that combining bempedoic acid with the lowest statin dose of commonly used statins would achieve a similar degree of LDL-C lowering as quadrupling that statin dose; for example, the predicted LDL-C lowering was 54% with atorvastatin 80 mg compared with 54% with atorvastatin 20 mg + bempedoic acid 180 mg, and 42% with simvastatin 40 mg compared with 46% with simvastatin 10 mg + bempedoic acid 180 mg.

CONCLUSION

These findings suggest bempedoic acid combined with lower statin doses offers similar LDL-C lowering compared with statin monotherapy at higher doses, potentially sparing patients requiring additional lipid-lowering therapies from the adverse events associated with higher statin doses.

Acute kidney injury in cystic fibrosis patients treated with intravenous colistimethate sodium or tobramycin

OBJECTIVES

Colistimethate sodium and tobramycin are important systemic antibiotics for treatment of cystic fibrosis (CF) pulmonary exacerbations but can induce acute kidney injury (AKI). We characterize the rate of AKI in CF patients treated with systemic colistimethate sodium compared with tobramycin.

METHODS

This single-centre, retrospective cohort study included hospitalized CF patients treated with IV colistimethate sodium or tobramycin. The primary outcome was AKI defined using the RIFLE criteria. Multivariate logistic regression using a mixed model was performed to identify variables that were independently associated with AKI.

RESULTS

Overall, 156 patients representing 507 care encounters were included. The OR of AKI was not increased with IV colistimethate sodium relative to IV tobramycin after adjusting for other potential predictor variables (aOR 1.00; 95% CI 0.16-6.03). The frequency of AKI was 9.5% across all encounters, 6.9% with IV colistimethate sodium and 9.9% with IV tobramycin, with RIFLE category R (risk) being the most common stage, accounting for 4.2% of encounters with IV colistimethate sodium and 9.2% with IV tobramycin. The concomitant use of another nephrotoxin (aOR 2.51; 95% CI 1.27-4.95) or the combination of vancomycin and piperacillin/tazobactam (aOR 5.95; 95% CI 2.05-17.3) were both associated with increased odds of AKI.

CONCLUSIONS

Systemic treatment with colistimethate sodium or tobramycin in the CF patient population is associated with a similar rate of nephrotoxicity. However, clinicians should be mindful of the increased risk for AKI in patients treated with either IV colistimethate sodium or IV tobramycin when used concurrently with other nephrotoxic agents, particularly the combination of vancomycin and piperacillin/tazobactam.

Pharmacokinetic/Pharmacodynamic Considerations of Alternate Dosing Strategies of Tocilizumab in COVID-19

Tocilizumab is one of few treatments that have been shown to improve mortality in patients with coronavirus disease 2019 (COVID-19), but increased demand has led to relative global shortages. Recently, it has been suggested that lower doses, or fixed doses, of tocilizumab could be a potential solution to conserve the limited global supply while conferring equivalent therapeutic benefit to the dosing regimens studied in major trials. The relationship between tocilizumab dose, exposure, and response in COVID-19 has not been adequately characterized. There are a number of pharmacokinetic (PK) parameters that likely differ between patients with severe COVID-19 and patients in whom tocilizumab was studied during the US FDA approval process. Likewise, it is unclear whether a threshold exposure is necessary for tocilizumab efficacy. The safety and efficacy of fixed versus weight-based dosing of tocilizumab has been evaluated outside of COVID-19, but it is uncertain if these observations are generalizable to severe or critical COVID-19. In the current review, we consider the potential advantages and limitations of alternative tocilizumab dosing strategies. Leveraging PK models and simulation analyses, we demonstrate that a fixed single dose of tocilizumab 400 mg is unlikely to produce PK exposures equivalent to those achieved in the REMAP-CAP trial, although weight-stratified dosing appears to produce more uniform exposure distribution. Data from current and future trials could provide PK/pharmacodynamic insight to better inform dosing strategies at the bedside. Ultimately, rational dosing strategies that balance available limited supply with patient needs are required.

Translation of Pharmacodynamic Biomarkers of Antibiotic Efficacy in Specific Populations to Optimize Doses

Antibiotic efficacy determination in clinical trials often relies on non-inferiority designs because they afford smaller study sample sizes. These efficacy studies tend to exclude patients within specific populations or include too few patients to discern potential differences in their clinical outcomes. As a result, dosing guidance in patients with abnormal liver and kidney function, age across the lifespan, and other specific populations relies on drug exposure-matching. The underlying assumption for exposure-matching is that the disease course and the response to the antibiotic are similar in patients with and without the specific condition. While this may not be the case, clinical efficacy studies are underpowered to ensure this is true. The current paper provides an integrative review of the current approach to dose selection in specific populations. We review existing clinical trial endpoints that could be measured on a more continuous rather than a discrete scale to better inform exposure-response relationships. The inclusion of newer systemic biomarkers of efficacy can help overcome the current limitations. We use a modeling and simulation exercise to illustrate how an efficacy biomarker can inform dose selection better. Studies that inform response-matching rather than exposure-matching only are needed to improve dose selection in specific populations.

Population pharmacokinetic analysis of apomorphine sublingual film or subcutaneous apomorphine in healthy subjects and patients with Parkinson's disease

Apomorphine is an on-demand treatment of "OFF" episodes in patients with Parkinson's disease (PD). A joint parent-metabolite population pharmacokinetic (PK) model characterized apomorphine and apomorphine-sulfate following administration of apomorphine sublingual film (APL) and two formulations of subcutaneous apomorphine. Overall, 2485 samples from 87 healthy subjects and 71 patients with PD and "OFF" episodes were analyzed using nonlinear mixed-effects modeling. Apomorphine PK was adequately described by a two-compartment model with first-order transit absorption via both routes of administration and first-order metabolism to apomorphine-sulfate with one-compartment disposition and first-order elimination. Bioavailability of apomorphine sublingual film was ~ 18% relative to subcutaneous apomorphine. Among covariates tested, only body weight had a large effect on apomorphine exposure (maximum plasma concentration and area under the concentration-time curve [AUC_0-∞ ]), with greater weight resulting in lower exposure. Model-predicted apomorphine exposure was similar between apomorphine sublingual film 30 mg and subcutaneous apomorphine 5 mg (median AUC_0-24 , 66.7 ng•h/mL, geometric mean ratio of 0.99; 90% confidence interval [CI], 0.96-1.03) and was comparable between apomorphine sublingual film 35 mg and subcutaneous apomorphine 6 mg (median AUC_0-24 , 75.4 and 80.0 ng•h/mL, respectively; geometric mean ratio of 0.94; 90% CI, 0.90-0.97) administered every 2 h for a maximum of 5 doses per day. In a typical patient with PD, predicted apomorphine exposure increased with increasing doses of apomorphine sublingual film; however, the increase was less than dose proportional. Similar apomorphine exposure was predicted in patients with mild renal impairment versus normal renal function. PK properties of apomorphine sublingual film support its administration for a wide range of patients with PD and "OFF" episodes, regardless of demographic and clinical characteristics.

Optimizing Estimated Glomerular Filtration Rate to Support Adult to Pediatric Pharmacokinetic Bridging Studies in Patients with Cystic Fibrosis

BACKGROUND

The estimated glomerular filtration rate (eGFR) is often used to model drug clearance (CL) and scale doses across age and body size. Over their lifetime, patients with cystic fibrosis (CF) receive repeated courses of tobramycin, an antibiotic with eGFR-dependent CL, for the treatment of pulmonary exacerbations. Tobramycin population pharmacokinetic (PK) modeling can be used to decipher the best approach to define eGFR for pediatric bridging studies.

METHODS

Inpatients with CF who received intravenous tobramycin between 1 January 2006 and 30 May 2018 were eligible for inclusion. Encounters without tobramycin concentration measurement or missing covariate data were excluded. Population PK analysis was performed using NONMEM.Covariate models were built  following identification of the base model, with specific emphasis on the effect of different methods of estimating renal function as a covariate of tobramycin CL.

RESULTS

A total of 296 CF patients contributed 1029 care encounters (420 pediatric, 609 adult) and 4352 tobramycin concentrations to this analysis. The median (minimum, maximum) age at encounter was 19 years (0.2, 60), with serum creatinine of 0.60 mg/dL (0.10, 3.41). A two-compartment model best described the observed data, with height and eGFR as significant covariates of tobramycin CL. eGFR was best modeled using a combination of the modified Schwartz and Chronic Kidney Disease Epidemiology Collaboration (CKDEPI) equations expressed in absolute units.

CONCLUSIONS

The CKDEPI equation bridges PK data generated in adults to adolescents with CF better than the current regulatory standard. The eGFR should be expressed in absolute units (mL/min) for PK analyses.

Renal Dosing of Antibiotics: Are We Jumping the Gun?

Antibiotic renal dose adjustments are determined in patients with stable chronic kidney disease and may not translate to patients in late-phase trials and practice. Ceftolozane/tazobactam, ceftazidime/avibactam, and telavancin all carry precautionary statements for reduced clinical response in patients with baseline creatinine clearance of 30-50 mL/min, potentially due to unnecessary dose reduction in the setting of acute kidney injury (AKI). In this review, we discuss the regulatory landscape for antibiotics eliminated by the kidney and highlight the importance of the first 48 hours of therapy. Using a clinical database, we identified AKI on admission in a substantial proportion of patients with pneumonia (27.1%), intraabdominal (19.5%), urinary tract (20.0%), or skin and skin structure infections (9.7%) that resolved by 48 hours in 57.2% of cases. We suggest that deferred renal dose reduction of wide therapeutic index antibiotics could improve outcomes in patients with infectious diseases.

Vancomycin volume of distribution estimation in adults with class III obesity

PURPOSE

To compare methods of estimating vancomycin volume of distribution (V) in adults with class III obesity.

METHODS

A retrospective, multicenter pharmacokinetic analysis of adults treated with vancomycin and monitored through measurement of peak and trough concentrations was performed. Individual pharmacokinetic parameter estimates were obtained via maximum a posteriori Bayesian analysis. The relationship between V and body weight was assessed using linear regression. Mean bias and root-mean-square error (RMSE) were calculated to assess the precision of multiple methods of estimating V.

RESULTS

Of 241 patients included in the study sample, 159 (66.0%) had a body mass index (BMI) of 40.0-49.9 kg/m2, and 82 (34.0%) had a BMI of ≥50.0 kg/m2. The median (5th, 95th percentile) weight of patients was 136 (103, 204) kg, and baseline characteristics were similar between BMI groups. The mean ± S.D. V was lower in patients with a BMI of 40.0-49.9 kg/m2 than in those with a BMI of ≥50.0 kg/m2 (72.4 ± 19.6 L versus 79.3 ± 20.6 L, p = 0.009); however, body size poorly predicted V in regression analyses (R2 < 0.20). A fixed estimate of V (75 L) and use of a weight-based value (0.52 L/kg by total body weight [TBW]) yielded similar bias and error in this population.

CONCLUSION

Results of the largest analysis of vancomycin V in class III obesity to date indicated that use of a fixed V value (75 L) and use of a TBW-based estimate (0.52 L/kg) for estimation of vancomycin V in patients with a BMI of ≥40.0 kg/m2 have similar bias. Two postdistribution vancomycin concentrations are needed to accurately determine patient-specific pharmacokinetic parameters, estimate area under the curve, and improve the precision of vancomycin dosing in this patient population.

Evolution of Equations for Estimating Renal Function and Their Application to the Dosing of New Antimicrobials

Objective: To address the background and rationale for the recent introduction of the Modification of Diet in Renal Disease (MDRD) equation for renal dose adjustment of antimicrobials and to provide recommendations for pharmacists dosing new antimicrobial agents. Data Sources: Comprehensive MEDLINE and EMBASE literature searches (from August 2018 to October 2019) were performed. Search terms included creatinine clearance, Cockcroft-Gault, MDRD, and glomerular filtration rate and a subsequent search included the preceding terms AND antimicrobials OR antibiotics. Study Selection and Data Extraction: Available English-language studies on the derivation and/or use of the Cockcroft-Gault (CG) and MDRD study equation were evaluated as well as those that specifically discussed their use for dosing antimicrobial agents. Data Synthesis: The US Food and Drug Administration (FDA) approval of delafloxacin and meropenem-vaborbactam in 2017 ushered in a new era in renal dosing of antibiotics, in that both agents are recommended to be dosed by the MDRD equation. Studies demonstrate that the CG and MDRD equations can result in discrepant dosing recommendations. Relevance to Patient Care and Clinical Practice: The renal estimation equation recommended in a new antibiotic label should dictate the dosing of that medication. It is noteworthy that these equations are not interchangeable. Conclusion: Recently approved antimicrobials utilizing the MDRD equation for renal dose adjustment will be interspersed with old and new antimicrobials utilizing the CG equation because of lack of singular guidance by the FDA. This requires pharmacists to be vigilant in evaluating drug labels to determine which equation is recommended and to understand the differences, strengths, and limitations of each equation.

Development of a sensitive LC-MS/MS method for quantification of linezolid and its primary metabolites in human serum

Linezolid (LZD) is a widely used antimicrobial that is active against a broad range of disease-causing bacteria. Myelosuppression is major treatment-limiting toxicity of LZD that occurs more frequently in patients with renal insufficiency. Quantification of LZD and its two primary metabolites (PNU-142300 and PNU-142586), which undergo significant renal elimination, may support design of improved dosing strategies to mitigate the risk of myelosuppression. In this study, we established the first liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of LZD and its main metabolites in human serum. Proteins in serum samples were precipitated with acetonitrile containing a deuterated internal standard. Chromatographic separation of analytes was performed with Waters X-bridge column (C18, 150 × 4.6 mm, 3.5 μm) at 25 °C and subjected to mass analysis using positive electro-spray ionization. The mobile phase A was water with 0.1% formic acid, and mobile phase B was acetonitrile with 0.1% formic acid at a flow rate of 0.6 mL/min, within a 15 min run time. Standard curves were linear and correlation coefficients (r²) were ≥0.99 for concentration ranges of 0.1-50 μg/mL for LZD and PNU-142300, and 0.1-25 μg/mL for PNU-142586. The inter- and intra-assay precisions were <15% for all analytes in quality control samples, and the accuracies ranged from 97 to 112%. Extraction recoveries ranged from 78 to 103% for all analytes, and there was no significant matrix effect. Samples from 10 patients (5 with renal impairment) were assayed. Mean (SD) LZD, PNU-142300 and PNU-142586 trough concentrations were 19.4(6.8), 11.6(6.8), 25.7(16.4) μg/mL, respectively, in patients with renal impairment. These values were 2.5-, 5.8-, and 6.8-fold higher for LZD, PNU-142300 and PNU-142586, respectively compared to patients without renal impairment. The method was effectively applied in the determination of LZD and its main metabolites in human serum.

1035. Implementation of an Antimicrobial Stewardship Program-Led, Multifactorial Pneumonia Diagnosis and Treatment Bundle

Background

Pneumonia remains a leading cause of hospitalization and accounts for significant antibiotic use. This study aims to evaluate the impact of bundled antimicrobial stewardship program (ASP) interventions, including procalcitonin and surveillance cultures, on broad-spectrum antimicrobial use in patients with suspected pneumonia.

Methods

This is a pre-post, quasi-experimental study conducted at Michigan Medicine. During the intervention period, an ASP member reviewed adult patients admitted to 3-floor medical services with antibiotics initiated for suspected pneumonia. The ASP member (1) recommended the use of procalcitonin when clinically appropriate, (2) used institutional guidelines to guide empiric antibiotic selection based on risk for drug-resistant pathogens, and (3) ordered a methicillin-resistant Staphylococcus aureus (MRSA) surveillance culture in patients receiving empiric anti-MRSA therapy. The primary endpoint was anti-MRSA and anti-pseudomonal (PSA) antibiotic use measured as days of therapy (DOT) per 1000 days-present on the services of interest. Antibiotic use and clinical data were extracted from an electronic database. Pneumonia diagnosis codes were used to identify the study population.

Results

A total of 549 patients were included: 310 in the pre-intervention (December 1/2017 - 3/31/2018) and 239 in the intervention (December 1/2018 - 3/31/2019) periods. Baseline demographics were similar between groups (Table 1). Less than 15% of patients had a microbiological diagnosis via respiratory culture in both study periods (Table 2). Respiratory cultures were ordered less commonly in the intervention period; however, the rate of culture positivity was higher (28% vs. 48%, P < 0.01). Process measures improved in the intervention period with an increase in the proportion of patients with MRSA surveillance cultures (13% vs. 39%, P < 0.01) and procalcitonin monitoring (77% vs. 83%, P = 0.07). Compared with the pre-intervention period, anti-MRSA antibiotic use decreased from 172 to 158 DOT per 1000 days-present (Δ -8%) and the use of anti-PSA antibiotics decreased from 348 to 316 DOT per 1000 days present (Δ -9%).

Conclusion

The implementation of an ASP-led pneumonia bundle led to reductions in anti-MRSA and anti-PSA antibiotic use.

Disclosures

All authors: No reported disclosures.

Pharmacokinetics and Pharmacodynamics of β-Lactamase Inhibitors

Novel β-lactamase inhibitors have extended the reach of new and existing β-lactams against multidrug-resistant bacteria expressing β-lactamases. The efficacy of these combination therapeutics relies on a complex two-component pharmacodynamic (PD) system where the β-lactamase inhibitor inactivates the bacterial β-lactamase enzyme and frees the companion β-lactam to act against its penicillin-binding protein target. Despite considerable investigation into the pharmacokinetics (PK) and pharmacodynamics of β-lactams, the pharmacology of their companion β-lactamase inhibitors has only recently been rigorously explored. This review describes the diversity of β-lactamase enzymes, mechanisms of enzyme inhibition, and factors impacting the efficacy of clinically available β-lactamase inhibitors. Relevant PK differences among available inhibitors and the PK/PD properties of these agents are described independently of their companion β-lactams. In the modern era of antibiotic resistance, a comprehensive understanding of the pharmacology, PK, and PD of β-lactamase inhibitors is paramount to maximizing the therapeutic efficacy of existing β-lactam/β-lactamase inhibitor combinations and protecting novel agents in the drug development pipeline.

Individualizing piperacillin/tazobactam dosing in adult patients with cystic fibrosis: can tobramycin measurements help?

Background

Empirical models to predict β-lactam pharmacokinetics (PK) using information from routine aminoglycoside therapeutic drug monitoring (TDM) have been proposed for critically ill patients; however, no such models exist for patients with cystic fibrosis (CF).

Objectives

To investigate whether PK parameters of tobramycin could be used to predict those of piperacillin.

Methods

A non-interventional, open-label PK study was conducted in hospitalized adults treated with piperacillin/tazobactam and tobramycin for acute pulmonary exacerbations of CF. Six serum samples per patient were collected and analysed. One- and two-compartment population PK models with linear, Michaelis-Menten or mixed elimination were evaluated for both drugs within the PmetricsTM package for R. Models were developed and compared iteratively using the log-likelihood and Akaike information criterion (AIC) objective functions.

Results

Nine primarily female (n = 8) and Caucasian (100%) adult CF patients were enrolled. The median (IQR) age, height, weight and serum creatinine of included patients was 31 (27-32) years, 51.4 (49.9-55.8) kg, 162.6 (160.0-165.1)  cm and 0.6 (0.5-0.6) mg/dL, respectively. The final model with the lowest objective function values consisted of one compartment with first-order elimination for tobramycin and two compartments with mixed-order elimination for piperacillin with the elimination rate constant of piperacillin modelled as a linear function of the elimination rate constant of tobramycin.

Conclusions

A relationship was identified between the elimination rate constants of tobramycin and piperacillin. Validation of this relationship in larger studies of adult patients with CF is needed before application to the precision dosing of piperacillin/tazobactam in this patient population.

1416. Piperacillin/Tazobactam Therapeutic Drug Monitoring: True Interpatient Variability or Compound Instability?

Background

β-Lactam exposure is frequently documented to be inadequate in critically ill patients implying that therapeutic drug monitoring (TDM) may be necessary to optimize efficacy. Practical barriers to implementation of TDM for β-lactam/β-lactamase inhibitor combinations include potential chemical instability as well as the need to assay both drug components.

Methods

First, ex-vivo stability studies of piperacillin/tazobactam (PIP/TZB) were performed at 1, 10, and 100 mg/L concentrations in human plasma. Spiked plasma samples were stored at room temperature for 4 hours and then at 4°C for 72 hours to mimic the conditions of routine handling. Second, a pilot study using discarded clinical laboratory samples was conducted to ascertain the feasibility of such a method for PIP/TZB TDM. Consecutive patients initiated on PIP/TZB within 24 hours of admission to the medical intensive care unit were screened for enrollment. Patients receiving less than 48 hours of therapy and those requiring renal replacement therapy were excluded. Laboratory samples were collected following their intended use and assayed for PIP and TZB using LC-MS/MS. Clinical patient data were obtained retrospectively.

Results

In the ex vivo studies, both PIP and TZB were stable at 100 mg/L for up to 48 hours at 4°C; however, at lower drug concentrations there was unacceptable (>15%) loss after 24 hours. Thirty-two subjects contributed a total of 136 clinical samples for secondary analysis. Patients were a mean (SD) of 64 (15) years old with estimated creatinine clearance of 97 (61) mL/minute. The assay was linear over a range of 1–100 μg/mL and 0.5–50 μg/mL for PIP and TZB, respectively. The median (fifth, 95th percentile) PIP and TZB concentrations were 26.30 (1.78, 112.00) and 7.55 (0.95, 23.00) mg/L, respectively. A strong linear relationship (R² 0.84) was found between TZB and PIP concentrations (figure).

Conclusion

PIP and TZB concentrations are strongly correlated permitting evaluation of PIP as the key analyte. Plasma samples for PIP/TZB should be frozen soon after collection for batch assay Methods. “Real-world” studies documenting high interpatient variability in PIP/TZB pharmacokinetics in the critically ill should account for pre-analytical variation due to sample degradation with clear sample handling protocols.

Disclosures

All authors: No reported disclosures.

Estimating Renal Function in Drug Development: Time to Take the Fork in the Road

Renal function is the most commonly applied patient-specific quantitative variable used to determine drug doses. Measurement of renal function is not practical in most clinical settings; therefore, clinicians often rely on estimates when making dosing decisions. Similarly, renal function estimates are used to assign subjects in phase 1 pharmacokinetic studies, which inform dosing in late-phase clinical trials and ultimately the product label. The Cockcroft-Gault estimate of creatinine clearance has been the standard renal function metric; however, this paradigm is shifting toward the Modification of Diet in Renal Diseases (MDRD) estimate of the glomerular filtration rate (GFR). The proportion of approved new drug labels with dosing recommendations based on the MDRD equation was 16.7% in 2015, 70.0% in 2016, and 46.7% in 2017. Disharmonious recommendations from the United States Food and Drug Administration and the European Medicines Agency will continue to increase this heterogeneity in the assessment of renal function in drug development and negatively impact industry, health systems, and clinicians. In this review, we discuss the current regulatory guidance for the conduct of renal impairment pharmacokinetic studies and review the implications of this guidance across the medication use system with 3 recently approved antibiotics: ceftazidime/avibactam, delafloxacin, and meropenem/vaborbactam. Finally, we suggest measuring GFR in phase 1 studies and employing the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to integrate data across clinical trials. This will help to harmonize CKD staging, population pharmacokinetic analyses, and dosing by estimated renal function.

Curricular Reform in Pharmacy Education Through the Lens of the Flexner Report of 1910

Abraham Flexner's 1910 report on medical education in the United States (US) and Canada propelled medical training forward into a contemporary renaissance. The report heralded many seismic changes that still resonate within medical and health professions education throughout the US. Today several factors are accelerating curricular reform within pharmacy education, including but not limited to accreditation standards, technologic advances, and student diversity. Despite the fact that Flexner's report is now over a century old, many of his observations and recommendations regarding education are as pertinent and timely today as they were in 1910. This commentary will discuss and reflect upon curricular reform in pharmacy education as it contrasts with some of the observations, findings, and recommendations of Flexner's 1910 report.

Use of Premixed Parenteral Nutrition During a Phosphate Shortage in a Non-Critically Ill Population

BACKGROUND

Drug shortages pose prescribing problems to clinicians. During fiscal year (FY) 2014, an acute shortage of intravenous potassium phosphate (K-Phos IV), a common supplement in parenteral nutrition (PN), prompted the use of premixed instead of individualized PN to conserve K-Phos IV. Here we quantify the K-Phos IV conserved by using premixed PN and the associated cost differences.

MATERIALS AND METHODS

Costs of preparing premixed PN vs individualized PN of equivalent composition were calculated for FY 2014 at a single-center tertiary care facility. Quantity and cost of K-Phos IV saved were calculated based on the number of premixed PN prescriptions. Costs for FY 2015 were projected based on drug costs from July 2014.

RESULTS

During FY 2014, prescribing premixed in lieu of individualized PN conserved 16,440 mmol K-Phos IV but increased the cost of PN by $4080.45. However, increases in K-Phos IV cost at the end of FY 2014 resulted in premixed PN as a relatively less expensive therapy than individualized PN for our institution. Cost savings of $7092.20 due to use of premixed PN is projected for FY 2015.

CONCLUSIONS

Prescribing premixed PN conserves K-Phos IV during shortages, but it increased direct drug spending in non-critically ill patients at our institution during FY 2014. Persistent shortages can drive market costs of K-Phos IV, however, necessitating frequent reconsideration of resource utilization.