National survey of extended-interval aminoglycoside dosing in pediatric cystic fibrosis pulmonary exacerbations

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

OBJECTIVES

Sophisticated 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 aimed to determine current TDM practice for tobramycin monitoring in cystic fibrosis (CF) centres in the USA and Canada, UK and Ireland, and Australia and New Zealand due to a high prevalence of CF.

METHODS

A web-based survey was developed and circulated via CF specialist groups within the targeted geographical regions. Themes included centre demographics, tobramycin usage, dosing and infusion practices, TDM practices, and blood sampling methods.

RESULTS

In total 77 responses were received from 75 different CF centres over the 3-month evaluation period (October 2019-January 2020). Respondents were from the USA and Canada (60%), Australia and New Zealand (25%), and the UK and Ireland (15%). Tobramycin was used in 97% of sites, with an international variation in practice across all survey aspects including dosing and infusion practice. TDM-based dose adjustment in the UK and Ireland was most commonly based only on trough sample collection for avoidance of toxicity, where use of computer programs for targeting both efficacy and toxicity endpoints were most common in Australia and New Zealand. The underlying pharmacokinetic basis of that program was not known by 33% of sites who utilised a computer program for tobramycin dose individualisation.

CONCLUSION

There remains substantial heterogeneity in tobramycin management worldwide. Despite two decades of research into TDM of tobramycin, there has been a slow uptake of new technologies and evolution of practice. An improved understanding of TDM processes is required for translation of evidence-based research into clinical practice. International guidelines require updating due to the advances in research to support confidence in the changes in clinical practice.

The indispensable role of pharmacy services and medication therapy management in cystic fibrosis

Care for people with cystic fibrosis (PWCF) is highly complex and requires a multidisciplinary approach where the pharmacist plays a vital role. The purpose of this manuscript is to serve as a guideline for pharmacists and pharmacy technicians who provide care for PWCF by providing background and current recommendations for the use of cystic fibrosis (CF)-specific medications in both the acute and ambulatory care settings. The article explores current literature surrounding the role of pharmacists and pharmacy technicians, proven pharmacy models to emulate, and pharmacokinetic idiosyncrasies unique to the CF population while also identifying areas of future research. Clinical recommendations for the use of CF-specific medications are broken down by organ system including mechanism of action, adverse events, dosages, and monitoring parameters. The article also includes quick reference tables essential to the acute and chronic medication therapy management of PWCF.

Aminoglycoside dosing and monitoring for Pseudomonas aeruginosa during acute pulmonary exacerbations in cystic fibrosis

Aminoglycosides are commonly used for the treatment of Pseudomonas aeruginosa (PsA) in the setting of acute pulmonary exacerbations (PEx) in pediatric patients with cystic fibrosis (CF). There are controversies and practice differences between institutions related to aminoglycoside dosing and monitoring strategies. The purpose of this review article is to summarize the currently available literature and identify gaps in the literature related to pharmacokinetic parameter goals, aminoglycoside dosing strategies, and methods for monitoring serum aminoglycoside concentrations for treatment of PsA in CF PEx, and throughout will discuss anticipated changes with the increasing availability of highly effective CF transmembrane conductance regulator modulators. This review focuses on tobramycin, as it is the most commonly used aminoglycoside in CF PEx, and will briefly discuss special circumstances surrounding use of amikacin and gentamicin.

Clinical Considerations for Routine Auditory and Vestibular Monitoring in Patients With Cystic Fibrosis

Purpose Specific classes of antibiotics, such as aminoglycosides, have well-established adverse events producing permanent hearing loss, tinnitus, and balance and/or vestibular problems (i.e., ototoxicity). Although these antibiotics are frequently used to treat pseudomonas and other bacterial infections in patients with cystic fibrosis (CF), there are no formalized recommendations describing approaches to implementation of guideline adherent ototoxicity monitoring as part of CF clinical care. Method This consensus statement was developed by the International Ototoxicity Management Working Group (IOMG) Ad Hoc Committee on Aminoglycoside Antibiotics to address the clinical need for ototoxicity management in CF patients treated with known ototoxic medications. These clinical protocol considerations were created using consensus opinion from a community of international experts and available evidence specific to patients with CF, as well as published national and international guidelines on ototoxicity monitoring. Results The IOMG advocates four clinical recommendations for implementing routine and guideline adherent ototoxicity management in patients with CF. These are (a) including questions about hearing, tinnitus, and balance/vestibular problems as part of the routine CF case history for all patients; (b) utilizing timely point-of-care measures; (c) establishing a baseline and conducting posttreatment evaluations for each course of intravenous ototoxic drug treatment; and (d) repeating annual hearing and vestibular evaluations for all patients with a history of ototoxic antibiotic exposure. Conclusion Increased efforts for implementation of an ototoxicity management program in the CF care team model will improve identification of ototoxicity signs and symptoms, allow for timely therapeutic follow-up, and provide the clinician and patient an opportunity to make an informed decision about potential treatment modifications to minimize adverse events. Supplemental Material https://doi.org/10.23641/asha.16624366.

Functional Impacts of Aminoglycoside Treatment on Speech Perception and Extended High-Frequency Hearing Loss in a Pediatric Cystic Fibrosis Cohort

Purpose The purpose of this study is to better understand the prevalence of ototoxicity-related hearing loss and its functional impact on communication in a pediatric and young adult cohort with cystic fibrosis (CF) and individuals without CF (controls). Method We did an observational, cross-sectional investigation of hearing function in children, teens, and young adults with CF (n = 57, M = 15.0 years) who received intravenous aminoglycoside antibiotics and age- and gender-matched controls (n = 61, M = 14.6 years). Participants completed standard and extended high-frequency audiometry, middle ear measures, speech perception tests, and a hearing and balance questionnaire. Results Individuals with CF were 3-4 times more likely to report issues with hearing, balance, and tinnitus and performed significantly poorer on speech perception tasks compared to controls. A higher prevalence of hearing loss was observed in individuals with CF (57%) compared to controls (37%). CF and control groups had similar proportions of slight and mild hearing losses; however, individuals with CF were 7.6 times more likely to have moderate and greater degrees of hearing loss. Older participants displayed higher average extended high-frequency thresholds, with no effect of age on average standard frequency thresholds. Although middle ear dysfunction has not previously been reported to be more prevalent in CF, this study showed that 16% had conductive or mixed hearing loss and higher rates of previous otitis media and pressure equalization tube surgeries compared to controls. Conclusions Individuals with CF have a higher prevalence of conductive, mixed, and sensorineural hearing loss; poorer speech-in-noise performance; and higher rates of multiple symptoms associated with otologic disorders (tinnitus, hearing difficulty, dizziness, imbalance, and otitis media) compared to controls. Accordingly, children with CF should be asked about these symptoms and receive baseline hearing assessment(s) prior to treatment with potentially ototoxic medications and at regular intervals thereafter in order to provide otologic and audiologic treatment for hearing- and ear-related problems to improve communication functioning.

Optimization of a Meropenem-Tobramycin Combination Dosage Regimen against Hypermutable and Nonhypermutable Pseudomonas aeruginosa via Mechanism-Based Modeling and the Hollow-Fiber Infection Model

Hypermutable Pseudomonas aeruginosa strains are prevalent in patients with cystic fibrosis and rapidly become resistant to antibiotic monotherapies. Combination dosage regimens have not been optimized against such strains using mechanism-based modeling (MBM) and the hollow-fiber infection model (HFIM). The PAO1 wild-type strain and its isogenic hypermutable PAOΔmutS strain (MIC_meropenem of 1.0 mg/liter and MIC_tobramycin of 0.5 mg/liter for both) were assessed using 96-h static-concentration time-kill studies (SCTK) and 10-day HFIM studies (inoculum, ∼10^8.4 CFU/ml). MBM of SCTK data were performed to predict expected HFIM outcomes. Regimens studied in the HFIM were meropenem at 1 g every 8 h (0.5-h infusion), meropenem at 3 g/day with continuous infusion, tobramycin at 10 mg/kg of body weight every 24 h (1-h infusion), and both combinations. Meropenem regimens delivered the same total daily dose. Time courses of total and less susceptible populations and MICs were determined. For the PAOΔmutS strain in the HFIM, all monotherapies resulted in rapid regrowth to >10^8.7 CFU/ml with near-complete replacement by less susceptible bacteria by day 3. Meropenem every 8 h with tobramycin caused >7-log₁₀ bacterial killing followed by regrowth to >6 log₁₀ CFU/ml by day 5 and high-level resistance (MIC_meropenem, 32 mg/liter; MIC_tobramycin, 8 mg/liter). Continuous infusion of meropenem with tobramycin achieved >8-log₁₀ bacterial killing without regrowth. For PAO1, meropenem monotherapies suppressed bacterial growth to <4 log₁₀ over 7 to 9 days, with both combination regimens achieving near eradication. An MBM-optimized meropenem plus tobramycin regimen achieved synergistic killing and resistance suppression against a difficult-to-treat hypermutable P. aeruginosa strain. For the combination to be maximally effective, it was critical to achieve the optimal shape of the concentration-time profile for meropenem.

Safety of Extended Interval Tobramycin in Cystic Fibrosis Patients Less an 6 Years Old

OBJECTIVES

The primary objective of this study was to assess the nephrotoxicity and ototoxicity risks of extended interval tobramycin in cystic fibrosis (CF) patients who are <6 years old. A secondary objective included analyzing pharmacokinetic parameters in this age group.

METHODS

A retrospective chart review was conducted of patients with CF who were <6 years old, admitted for an acute pulmonary exacerbation from January 1, 2003, to January 1, 2014, and treated with intravenous tobramycin.

RESULTS

The median baseline serum creatinine (SCr) was 0.26 mg/dL among the 31 patients included in the study. Of the 20 patients who experienced increases in SCr, the absolute median increase was 0.065 mg/dL (0.033-0.1 mg/dL). Abnormal audiograms seen in 4 patients are attributable to middle ear effusion present on exam. The median dose of tobramycin was 11.7 mg/kg (11.3-12 mg/kg), the elimination constant was 0.4 hr^-1(0.32-0.47 hr^-1), half-life was 1.7 hr (1.5-2.1 hr), volume of distribution was 0.37 L/kg (0.31-0.47 L/kg), and median peaks and troughs fell within ranges of 20 to 30 mg/L (20.9-32.7 mg/L) and <0.01 mg/L, respectively.

CONCLUSIONS

Extended interval dosing tobramycin is safe in CF patients who are <6 years old. There was no drug-related ototoxicity, and some nephrotoxicity was observed. When dosed at 12 mg/kg, similar pharmacokinetics were seen among all age groups, and concentrations were within the desired range.

Evaluation of the Risk for Acute Kidney Injury in Adult Cystic Fibrosis Patients Receiving Concomitant Vancomycin and Tobramycin

Background

The risk for acute kidney injury (AKI) has been associated with both tobramycin and vancomycin.

Objective

To determine whether the rate of drug therapy-related nephrotoxicity is greater in Cystic Fibrosis (CF) patients receiving concomitant vancomycin and tobramycin than patients receiving either agent alone.

Methods

Adult CF patients admitted for acute pulmonary exacerbation (APE) over a seven-year period (2008-2014), who received at least 72 hours of intravenous vancomycin, tobramycin or a combination of the two agents were evaluated for AKI. AKI was defined as a 1.5-fold increase in serum creatinine per RIFLE criteria. One hundred seventy-four hospital encounters from 72 unique patients were assessed in this single-center, cross-sectional study.

Results

AKI outcomes were not statistically different. AKI rates were 19% for vancomycin, 8.7% for tobramycin, and 19.7% for combination cohorts (p = 0.16).

Conclusion

Our data suggest there is no significant difference in AKI risk when vancomycin and tobramycin combination therapy is used.

Vancomycin Dosing and Monitoring in the Treatment of Cystic Fibrosis: Results of a National Practice Survey

OBJECTIVES

Vancomycin is commonly used in patients with cystic fibrosis (CF) to treat acute pulmonary exacerbations, but few guidelines exist to help dose and monitor patients. The objective of this study was to assess vancomycin use and monitoring strategies at Cystic Fibrosis Foundation (CFF)-accredited centers in hopes of developing and implementing vancomycin dosing and monitoring standards.

METHODS

An anonymous national cross-sectional survey of pharmacists affiliated with CFF-accredited pediatric and/or adult centers was performed by using Surveymonkey.com. The survey consisted of 3 sections: (1) CF Center Demographic Information (10 questions); 2) vancomycin use in pediatric CF patients (31 questions); and 3) vancomycin use in adult CF patients (29 questions); it was administered from March 9, 2015, to April 13, 2015.

RESULTS

The survey was completed by 31/69 (45%) pharmacists and 28 (90.3%) reported using vancomycin in the pediatric population. The most common initial starting dose for pediatric patients was 15 mg/kg/dose (57.1%) and every 6 hours was the most common dosing frequency (67.9%). The most common monitoring strategy was collection of a trough concentration (92.9%) with 57.7% of pharmacist targeting a range of 15 to 20 mg/L. The most common initial starting vancomycin dose in adults with CF was 15 mg/kg/dose (61.5%), and initial frequency of every 8 hours (73.1%). The most common monitoring strategy was a trough concentration (96.2%) with 83.3% of pharmacists reporting a goal trough range of 15 to 20 mg/L.

CONCLUSIONS

The most common vancomycin dosing reported was 15 to 20 mg/kg/dose every 6 hours (pediatric) and 15 to 20 mg/kg/dose every 8 to 12 hours (adults). Serum concentrations measured to meet monitoring parameters of trough concentrations of 15 to 20 mg/L, or area under the curve to minimum inhibitory concentration ratio > 400, were the same in both pediatric and adult patients.

Tobramycin and Beta-Lactam Antibiotic Use in Cystic Fibrosis Exacerbations: A Pharmacist Approach

OBJECTIVES

Survey suggests that recommended doses and dosage regimens for antipseudomonal antibiotics for the treatment of acute pulmonary exacerbations in cystic fibrosis (CF) patients are not used, and one way to address these disparities is the involvement of pharmacists who are dedicated to CF. This is the first survey specifically designed for pharmacists at Cystic Fibrosis Foundation (CFF)-accredited centers to identify how tobramycin and antipseudomonal beta-lactams are being used. The purpose of this survey is to quantify this information and to promote future study to allow for implementation of tobramycin and beta-lactam dosage and monitoring standardization.

METHODS

An anonymous national cross-sectional survey of pharmacists that are affliated with CFF-accredited programs was performed using Qualtrics.com.

RESULTS

The survey had a 48.5% response rate. Most pediatric pharmacists (78.6%) report using extended-interval tobramycin dosage. The most common reported starting dosage was 10 mg/kg every 24 hours; most centers aim for a maximum serum concentration (Cmax) between 20 and 40 mg/L (78.6%). A total of 26 adult pharmacists reported using extended-interval dosage (96%), using an initial dosage of 10 mg/kg/day. The most common parameters used to adjust dosage were Cmax and area under the curve (AUC; 31%); the Cmax goal was 20 to 40 mg/L (84.2%). Most respondents (79%) report using beta-lactams in combination with tobramycin. Extended-infusion and continuous-infusion beta-lactams were used more in adults than pediatric patients.

CONCLUSIONS

Most CF pharmacists report using extended-interval tobramycin. With the information from this survey, the establishment of future consensus recommendations by pharmacists for optimal and consistent tobramycin and antipseudomonal beta-lactam dosage and monitoring strategies needs to be considered.

Extended-Interval Aminoglycoside Use in Cystic Fibrosis Exacerbation in Children and Young Adults: A Prospective Quality Improvement Project

This is a prospective quality improvement project for patients with cystic fibrosis who are 5 years of age and older who were admitted for intravenous antibiotic administration as part of treatment of cystic fibrosis exacerbation. The goal of this project was to compare the pharmacokinetics of once-daily versus thrice-daily aminoglycoside use when treating cystic fibrosis exacerbation in different age groups. Of the total of 119 patient encounters, 82.4% were started on once-daily dosing, and the remainder were started on thrice-daily dosing. Patients with pharmacokinetics allowing the continuation of once-daily dosing differed from patients who required a switch to thrice-daily dosing in terms of baseline forced expiratory volume in 1 second, forced expiratory flow from 25% to 75% of vital capacity, age, and body mass index (BMI) but were similar in BMI percentiles. The once-daily dosing group had higher mean 18-hour level, higher mean half-life, higher mean area under the curve, and lower mean elimination constant. This study showed that aminoglycoside clearance is higher in younger children.

Optimized antimicrobial dosing strategies: a survey of pediatric hospitals

BACKGROUND

Extended-interval aminoglycoside (EIAG) and extended- and continuous-infusion β-lactam (EIBL and CIBL) dosing strategies are increasingly used in adults, but pediatric literature is limited.

OBJECTIVE

The objective of this study was to describe the use of EIAG, EIBL, and CIBL dosing in pediatric hospitals in the USA.

STUDY DESIGN, SETTING, AND PARTICIPANTS

A national survey of children's hospitals was conducted. A single practitioner from each target hospital was identified through the Children's Hospital Association. Practice-based survey questions identified whether hospitals utilize EIAG, EIBL, and CIBL dosing.

MAIN OUTCOME MEASURE

The main outcome measure was the percentage utilization of the dosing strategies, with secondary outcomes being the reasons for not using these dosing strategies.

RESULTS

Seventy-seven of 215 identified practitioners (36 %) participated in the survey. EIAG, EIBL, and CIBL dosing were utilized in 63 %, 24 %, and 13 % of responding hospitals, respectively. The most common reasons for not using EIAG were concern regarding lack of efficacy data (56 %) and concern regarding the duration of the drug-free period (41 %). Respondents who did not utilize EIBL cited concern due to lack of pediatric EIBL efficacy data (54 %), the need for more intravenous access (54 %), intravenous medication compatibility issues (39 %), and the time during which the patient is attached to an intravenous infusion (31 %).

CONCLUSION

This survey of children's hospitals indicates that EIAG is used in over 50 % of hospitals, but there is some lag in adoption of EIBL and CIBL dosing, both of which are used in fewer than 25 % of hospitals. Additional studies may provide much-needed evidence to increase the utilization of these strategies.