Stability and compatibility of vancomycin for administration by continuous infusion

Systematic Review of Piperacillin-Tazobactam and Vancomycin Y-Site Compatibility: Consideration of Concentration and Solution Variability

Simultaneous administration of vancomycin and piperacillin-tazobactam (VPT) poses significant challenges related to physical and chemical compatibility, as well as clinical practice. A systematic review of available literature related to VPT Y-site compatibility was performed. Data was collected from primary and tertiary sources. Seven articles were included in addition to one internal assessment and one review article and information from tertiary drug databases. The literature supports the simultaneous administration via Y-site of piperacillin-tazobactam 33.75 mg/mL in normal saline (NS) and vancomycin 4 to 8 mg/mL in NS. The same drug products at differing concentrations, diluents, storage conditions, or preparations outside of this recommendation should be considered incompatible.

New Weapons to Fight against Staphylococcus aureus Skin Infections

The treatment of Staphylococcus aureus skin and soft tissue infections faces several challenges, such as the increased incidence of antibiotic-resistant strains and the fact that the antibiotics available to treat methicillin-resistant S. aureus present low bioavailability, are not easily metabolized, and cause severe secondary effects. Moreover, besides the susceptibility pattern of the S. aureus isolates detected in vitro, during patient treatment, the antibiotics may never encounter the bacteria because S. aureus hides within biofilms or inside eukaryotic cells. In addition, vascular compromise as well as other comorbidities of the patient may impede proper arrival to the skin when the antibiotic is given parenterally. In this manuscript, we revise some of the more promising strategies to improve antibiotic sensitivity, bioavailability, and delivery, including the combination of antibiotics with bactericidal nanomaterials, chemical inhibitors, antisense oligonucleotides, and lytic enzymes, among others. In addition, alternative non-antibiotic-based experimental therapies, including the delivery of antimicrobial peptides, bioactive glass nanoparticles or nanocrystalline cellulose, phototherapies, and hyperthermia, are also reviewed.

Evaluation of Strategies for Reducing Vancomycin-Piperacillin/Tazobactam Incompatibility

BACKGROUND

Drug incompatibility is defined as a physical-chemical reaction between two or more injectable drugs and that results mainly in precipitation or insolubility. Several strategies for reducing incompatibilities have been implemented empirically in intensive care units. However, these strategies have never been compared directly (and particularly in terms of the particulate load and drug mass flow rate) under standardized conditions. The objective of the present in vitro study was to evaluate the impact of various strategies for preventing incompatibility between simultaneously infused vancomycin and piperacillin/tazobactam.

METHODS

An in-line filter, a dilute vancomycin solution (5 mg/mL), and an alternative saline administration line were evaluated separately. The infusion line outlet was connected to a dynamic particle counter. The antibiotic concentration was measured in an HPLC-UV assay.

RESULT

The use of an in-line filter and an alternative saline administration route did not significantly reduce the particulate load caused by vancomycin-piperacillin/tazobactam incompatibility. Dilution of the vancomycin solution was associated with a significantly lower particulate load and maintenance of the vancomycin mass flow rate.

DISCUSSION

It is important to systematically compare the efficacy of strategies for preventing drug incompatibility. The use of diluted vancomycin solution gave the best results in the case of vancomycin-piperacillin/tazobactam incompatibility.

Simple and rapid method for analysis of urinary vancomycin using solid phase extraction and fluorescence spectroscopy

Vancomycin (VCM) is an antimicrobial that is recommended for therapeutic drug monitoring (TDM) for maintaining the efficacy and safety of treatment. The trough monitoring has been used to guide VCM dosing regimens. However, newer guidelines recommend the use of area under the curve/minimum inhibitory concentration (AUC/MIC)-guided vancomycin dosing, and there is a need for easier and more frequent measurements of VCM concentrations. Therefore, in this study, we developed a simple and rapid analytical method for measuring urinary VCM by combining solid-phase extraction and fluorescence analysis. Urine samples are easier and less invasive than blood samples. In addition to the therapeutic range of blood VCM, this method was also able to measure 0.01–1 mg/mL, which is the concentration range of urinary VCM. The accuracy of 10, 20, and 30 μg/mL VCM solutions were between 93.18 and 109.76%. The relative standard deviation (RSD) of intra-day and inter-day analysis were less than 6.25% and 6.28%, respectively. Since this method does not use large equipment, it is expected to be better suited for clinical use.

Risk Factors for Nephrotoxicity in Methicillin-Resistant Staphylococcus aureus Bacteraemia: A Post Hoc Analysis of the CAMERA2 Trial

BACKGROUND

Clinical risk factors for nephrotoxicity in Staphylococcus aureus bacteraemia remain largely undetermined, despite its common occurrence and clinical significance. In an international, multicentre, prospective clinical trial (CAMERA2), which compared standard therapy (vancomycin monotherapy) to combination therapy (adding an anti-staphylococcal beta-lactam) for methicillin-resistant S. aureus bacteraemia, significantly more people in the combination therapy arm experienced acute kidney injury compared with those in the monotherapy arm (23% vs 6%).

OBJECTIVE

The aim of this post hoc analysis was to explore in greater depth the risk factors for acute kidney injury from the CAMERA2 trial.

METHODS

Among participants of the CAMERA2 trial, demographic-related, infection-related and treatment-related risk factors were assessed for their relationship with acute kidney injury by univariable and multivariable logistic regression. Acute kidney injury was defined by a modified-KDIGO (Kidney Disease: Improving Global Outcomes) criteria (not including urinary output).

RESULTS

Of the 266 participants included, age (p = 0.04), randomisation to combination therapy (p = 0.002), vancomycin area under the concentration-time curve (p = 0.03) and receipt of (flu)cloxacillin as the companion beta-lactam (p < 0.001) were significantly associated with acute kidney injury. On a multivariable analysis, concurrent use of (flu)cloxacillin increased the risk of acute kidney injury over four times compared with the use of cefazolin or no beta-lactam. The association of vancomycin area under the concentration-time curve with acute kidney injury also persisted in the multivariable model.

CONCLUSIONS

For participants receiving vancomycin for S. aureus bacteraemia, use of (flu)cloxacillin and increased vancomycin area under the concentration-time curve were risk factors for acute kidney injury. These represent potentially modifiable risk factors for nephrotoxicity and highlight the importance of avoiding the use of concurrent nephrotoxins.

Continuous Vancomycin Infusion versus Intermittent Infusion in Critically Ill Patients

Background

Vancomycin is the best-choice medication for methicillin-resistant staphylococcal and enterococcal infections, which are major problems in intensive care units (ICUs). Intermittent infusion is standard for vancomycin, although delayed therapeutic target achievement and supra- and subtherapeutic levels are concerns. A recently proposed alternative with superior therapeutic target achievement is continuous infusion.

Objective

To compare the benefits of continuous (CVI) and intermittent (IVI) vancomycin infusion.

Methods

This quasi-experimental study used propensity score-matched historical controls and adult patients in medical and surgical ICUs for whom vancomycin was indicated. The experimental group received CVI for ≥ 48 hours. Data on patients receiving IVI between January 2018 and October 2020 were reviewed. Capability to achieve serum vancomycin therapeutic targets (48 and 96 hours), episodes of supra- and subtherapeutic levels, treatment success, mortality, and incidence of acute kidney injury (AKI) were analyzed before and after one-to-two propensity score matching.

Results

The CVI group had 31 patients, while the unmatched IVI group had 125. More CVI patients achieved the therapeutic target within 48 hours (54.8% vs 25.6%; P=0.002). CVI patients had a higher median number of supratherapeutic episodes (2 vs 1; P=0.007) but a lower median for subtherapeutic episodes (0 vs 1; P=0.003). Other outcomes demonstrated no differences. After propensity score matching, target achievement within 48 hours (54.8% vs 22.6%; P=0.002) and fewer subtherapeutic episodes (0 vs 1; P=0.014) remained significant.

Conclusion

CVI's rapid therapeutic target achievement and fewer subtherapeutic episodes make it superior to IVI. No differences in treatment success, mortality, or AKI are evident.

Simultaneous infusion of two incompatible antibiotics: Impact of the choice of infusion device and concomitant simulated fluid volume support on the particulate load and the drug mass flow rates

Vancomycin and piperacillin/tazobactam are known to be incompatible. The objectives of the present study were to evaluate the impact of their simultaneous infusion on mass flow rates and particulate load and identify preventive strategies. We assessed both static conditions and a reproduction of an infusion line used in a hospital's critical care unit. A high-performance liquid chromatography/UV diode array system and static and dynamic laser diffraction particle counters were used. The mass flow rates were primarily influenced by the choice of the infusion device and the presence of simulated fluid volume support. Drug incompatibility also appeared to affect vancomycin's mass flow rate, and the dynamic particulate load increased during flow rate changes - especially in the infusion set with a large common volume line and no concomitant simulated fluid volume support. Only discontinuation of the piperacillin/tazobactam infusion was associated with a higher particulate load in the infusion set with a large common volume line and no concomitant simulated fluid volume support. A low common volume line and the use of simulated fluid volume support were associated with smaller fluctuations in the mass flow rate. The clinical risk associated with a higher particulate load must now be assessed.

Role of fluid status markers as risk factors for suboptimal vancomycin concentration during continuous infusion in neonates: an observational study

Vancomycin is widely used in neonatal sepsis but proportion of newborn reaching recommended concentration is variable. Fluid status impact on vancomycin level remains understudied. We aimed to study fluid factors impacting vancomycin concentration at 24 h of treatment. We performed a prospective and retrospective observational monocentric study of NICU patients requiring a vancomycin treatment. We used a continuous infusion protocol, with age-appropriate loading and maintenance doses. Vancomycin target serum concentration after 24 h (C_24h) was above 20 mg/L. Demographic, infections, and organ failure variables were analyzed as potential predictors of C_24h. Over the study period, 70 infective episodes in 52 patients were included. At treatment initiation, the median post-natal age was 12.5 days (IQR 7-23), post menstrual age 30 weeks (IQR 28-35), and median weight 1140 g (IQR 835-1722). Germs isolated were mainly gram-positive with 73.5% being coagulase-negative Staphylococci. Median C_24h was 18.7 mg/L (IQR 15.4-22.4). Overall, 41 (58.6%) treatments had a C_24h < 20 mg/L. After multivariate analysis, higher creatinine level (OR 1.03 (95% CI 1.002-1.06)) was associated with C_24h ≥ 20 mg/L; weight gain the day before infection (OR 0.21 (95% CI 0.05-0.79)) and positive biomarkers of inflammation (OR 0.22 (0.05-0.94)) were associated with C_24h < 20 mg/L.

CONCLUSION

Vancomycin C_24h was underdosed in 60% of patients and factors linked to changes in vancomycin pharmacokinetic such as volume of distribution and clearance, linked to creatinine level, inflammation, or weight gain, were identified.

WHAT IS KNOWN

• Adjustment of vancomycin regimen remains difficult due to inter- and intra-individual variability of vancomycin pharmacokinetics. • Impact of fluid status on vancomycin concentration in critically ill neonates is incompletely studied.

WHAT IS NEW

• Proportion of patients with adequate vancomycin concentration using a target adapted to nosocomial gram-positive bacteria MIC is low. • We confirmed the role of creatinine level and report two new factors associated with low vancomycin concentration: presence of systemic inflammation and weight gain.

Enantioseparation of linezolid and tedizolid using validated high-performance liquid chromatographic method

This paper reports the separation of two chiral antibacterial agents namely, linezolid and tedizolid using a validated high-performance liquid chromatographic method. In the current work, glycopeptide-based chiral column, CHIROBIOTIC® V2 (5-μm particle size, L × I.D. 25 cm × 4.6 mm) was employed with a mobile phase containing methanol and 0.15% aq. trifluoracetic acid (75:25%, v/v) in isocratic elution approach at flow rate of 1 ml min^-1 . The separation condition was customized (in terms of resolution values and retention times) was carried out by changing the content of the mobile phase, column temperature, flow rate, and so on. Results showed that the chromatographic separation was achieved within 15 min and average resolution values were 4.6 and 4.8 for tedizolid and linezolid, respectively. The detection limit values were 14.85 and 14.16 ng ml^-1 , respectively, for tedizolid enantiomers. Further, validation of separation parameters was performed by considering the international conference on harmonization guidelines, and ultimately, the mechanism of chiral recognition was also established.

Optimising an Infusion Protocol Containing Cefepime to Limit Particulate Load to Newborns in a Neonatal Intensive Care Unit

Background: In neonatal intensive care units (NICUs), the simultaneous administration of drugs requires complex infusion methods. Such practices can increase the risk of drug incompatibilities resulting in the formation of a particulate load with possible clinical consequences. Methods: This paper evaluates strategies to reduce the particulate load of a protocol commonly used in NICUs with a potential medical incompatibility (vancomycin/cefepime combination). The protocol was reproduced in the laboratory and the infusion line directly connected to a dynamic particle counter to evaluate the particulate matter administered during infusion. A spectrophotometry UV assay of cefepime evaluated the impact of filters on the concentration of cefepime administered. Results: A significant difference was observed between the two infusion line configurations used in the NICU, with higher particulate load for cefepime infused via the emergency route. There was no change in particulate load in the absence of vancomycin. A filter on the emergency route significantly reduced this load without decreasing the cefepime concentration infused. Preparation of cefepime seemed to be a critical issue in the protocol as the solution initially contained a high level of particles. Conclusion: This study demonstrated the impact of a reconstitution method, drug dilution and choice of infusion line configuration on particulate load.

Stability Evaluation of Extemporaneously Compounded Vancomycin Ophthalmic Drops: Effect of Solvents and Storage Conditions

Vancomycin is the drug of choice for methicillin-resistant Staphylococcus aureus keratitis and other ocular infections. Vancomycin ophthalmic drops are not commercially available and require compounding. The present study was designed to investigate the stability of vancomycin ophthalmic drops in normal saline, phosphate-buffered saline (PBS), and balanced salt solution (BSS) while stored at room temperature or under refrigeration. Vancomycin ophthalmic drops (50 mg/mL) were aseptically prepared from commercially available intravenous powder using PBS, BSS, and saline. Solutions were stored at room temperature and in a refrigerator for 28 days. The vancomycin stability was tested by a microbiology assay and high-performance liquid chromatography HPLC analysis immediately after formulation and at days 7, 14, and 28 after storage at room temperature or under refrigeration. The pH, turbidity was also tested. Vancomycin formulations in PBS, BSS and normal saline had initial pH of 5; 5.5; 3 respectively. The formulation in PBS developed turbidity and a slight decrease in pH upon storage. Microbiological assay did not show any change in zone of inhibition with any of the formulation upon storage either at room temperature or under refrigeration. HPLC analysis did not detect any decrease in vancomycin concentration or the accumulation of degraded products in any of the formulations upon storage either at room temperature or under refrigeration. Vancomycin ophthalmic drops prepared using PBS, BSS, and normal saline were stable up to the tested time point of 28 days, irrespective of their storage temperature.

Home intravenous antibiotherapy and the proper use of elastomeric pumps: Systematic review of the literature and proposals for improved use

Over several decades, the economic situation and consideration of patient quality of life have been responsible for increased outpatient treatment. It is in this context that outpatient antimicrobial treatment (OPAT) has rapidly developed. The availability of elastomeric infusion pumps has permitted prolonged or continuous antibiotic administration by dint of a mechanical device necessitating neither gravity nor a source of electricity. In numerous situations, its utilization optimizes administration of time-dependent antibiotics while freeing the patient from the constraints associated with infusion by gravity, volumetric pump or electrical syringe pump and, more often than not, limiting the number of nurse interventions to one or two a day. That much said, the installation of these pumps, which is not systematically justified, entails markedly increased OPAT costs and is liable to expose the patient to a risk of therapeutic failure or adverse effects due to the instability of the molecules utilized in a non-controlled environment, instability that necessitates close monitoring of their use. More precisely, a prescriber must take into consideration the stability parameters of each molecule (infusion duration, concentration following dilution, nature of the diluent and pump temperature). The objective of this work is to evaluate the different means of utilization of elastomeric infusion pumps in intravenous antibiotic administration outside of hospital. Following a review of the literature, we will present a tool for optimized antibiotic prescription, in a town setting by means of an infusion device.

Continuous Infusion Vancomycin in Pediatric Patients: A Critical Review of the Evidence

OBJECTIVE

To evaluate the use of continuous infusion vancomycin in pediatric patients.

DATA SOURCES AND STUDY SELECTION

PubMed, Cochrane Library, International Pharmaceutical Abstracts, and Google Scholar were searched to identify relevant published articles (1977 to November 2019) using the following search terms: vancomycin, neonates, pediatrics, infusion, continuous, administration, children, nephrotoxicity, pharmacokinetics, and pharmacodynamics. All English-language primary references that evaluated continuous infusion vancomycin in pediatric patients were included in this review.

DATA SYNTHESIS

Vancomycin is typically administered with intermittent infusions, but continuous infusion is an alternative delivery method used to improve achievement of target serum concentrations. Fifteen articles were reviewed that evaluated continuous infusion vancomycin in pediatric patients. Study data were heterogeneous with limited evidence to support improved clinical or microbiologic outcomes as compared with intermittent dosing. Potential benefits and limitations of continuous infusions are discussed.

CONCLUSIONS

Currently available evidence is lacking to support routine implementation of continuous infusion vancomycin in pediatric patients. However, it is a therapeutic option in certain clinical conditions and could be beneficial for individuals with serious Gram-positive infections where rapid achievement of target serum concentrations is critical. Continuous infusions may also benefit individuals who do not achieve target concentrations or who experience significant red man syndrome with traditional dosing, particularly when high daily doses are required. Optimal dosing and ideal target serum concentrations have not been established and may vary for different populations. Future prospective randomized clinical trials should be performed to identify optimal dosing and monitoring regimens and determine comparative safety and efficacy with traditional intermittent dosing in various pediatric populations.

Identifying Safety Hazards Associated With Intravenous Vancomycin Through the Analysis of Patient Safety Event Reports

Intravenous (IV) vancomycin is one of the most commonly used antibiotics in U.S. hospitals. There are several complexities associated with IV vancomycin use, including the need to have an accurate patient weight for dosing, to provide close monitoring to ensure appropriate drug levels, to monitor renal function, and to continue delivery of the medication at prescribed intervals. There are numerous healthcare system factors, including workflow processes, policies, health information technology, and clinical knowledge that impact the safe use of IV vancomycin. Past literature has identified several safety hazards associated with IV vancomycin use and there are some proposed solutions. Despite this literature, IV vancomycin–related safety issues persist. We analyzed patient safety event reports describing IV vancomycin–related issues in order to identify where in the medication process these issues were appearing, the type of medication error associated with each report, and general contributing factor themes. Our results demonstrate that recent safety reports are aligned with the issues already identified in the literature, suggesting that improvements discussed in the literature have not translated to clinical practice. Based on our analysis and current literature, we have developed a shareable infographic to improve clinician awareness of the complications and safety hazards associated with IV vancomycin and a self-assessment tool to support identification of opportunities to improve patient safety during IV vancomycin therapy. We also recommend development of clear guidelines to optimize health information technology systems to better support safe IV vancomycin use.

Chemical and Physical Stability of an Admixture Containing Cefepime and Vancomycin in Lactated Ringer Solution

Purpose: To evaluate the chemical and physical stability of an admixture containing cefepime and vancomycin in a single volume of lactated Ringer solution at refrigerated temperatures. Methods: Cefepime 2000 mg and vancomycin 1000 mg were, respectively, reconstituted with 10 and 20 mL of sterile water for injection (SWFI) per manufacturer instructions. This resulted in cefepime and vancomycin concentrations of 200 and 50 mg/mL, respectively. The resulting cefepime and vancomycin solutions at 10 and 20 mL, respectively, were drawn up and injected into 1000 mL lactated Ringer solution. Aliquot samples were obtained on days 0 to 9, visually inspected for gross incompatibility, and then stored at -80°C. Samples were thawed on the day of the analysis and run through ultraperformance liquid chromatography. Area under the concentration-time curve (AUC) on each day was compared with baseline AUC values. Chemical stability was defined as an AUC more than 93% of the baseline value. Results: No evidence of gross physical incompatibility was observed by visual inspection. Cefepime and vancomycin replicants were more than 94.5% and 98% of baseline AUC values. Therefore, all sample replicants were found to be more than 93% of their baseline AUC value. Conclusion: An admixture containing cefepime 2000 mg and vancomycin 1000 mg in 1000 mL lactated Ringer solution appears to be chemically and physically stable at refrigerated temperatures for up to 9 days.

Pharmacokinetic modelling and Bayesian estimation-assisted decision tools to optimize vancomycin dosage in neonates: only one piece of the puzzle

Introduction: Vancomycin is commonly administered to neonates, while observational data on therapeutic drug monitoring (TDM, trough levels) suggest that vancomycin exposure and dosage remain substandard. Area covered: Data on vancomycin pharmacokinetics (PK) and its covariates are abundant. Consequently, modeling is an obvious tool to improve targeted exposure, with a shift from TDM trough levels to area under the curve (AUC_24h) targets, as in adults. Continuous administration appeared as a practice to facilitate AUC_24h target attainment, while Bayesian model-supported targeting emerged as a novel tool. However, the AUC_24h/MIC (minimal inhibitory concentration) target itself should consider neonate-specific aspects (bloodstream infections, coagulase-negative staphylococci, protein binding, underexplored causes of variability, like assays, preparation and administration inaccuracies, or missing covariates). Expert opinion: To improve targeted exposure in neonates, initial vancomycin prescription should be based on 'a priori model-based individual dosing' using validated dosing regimens, followed by further tailoring by dosing optimization applying Bayesian estimation-assisted TDM. Future research should focus on the feasibility to integrate these tools (individualized dosing, Bayesian models) in clinical practice, and to perform PK/PD studies in the relevant animal models and human neonatal setting (coagulase-negative staphylococci, bloodstream infections).

Experience with Continuous Infusion Vancomycin Dosing in a Large Pediatric Hospital

BACKGROUND

There is a paucity of data on dosing of continuous infusion of vancomycin (CIV) in pediatric patients, despite it being an attractive treatment option for limiting escalating doses of intermittent infusion of vancomycin. The purpose of this study was to determine the total daily dose of CIV required to attain therapeutic serum vancomycin concentrations (SVCs) in pediatric patients according to age (≥31 days to <2 years, 2 to <8 years, and 8 to <18 years).

METHODS

We retrospectively evaluated patients who were transitioned from intermittent infusion of vancomycin to CIV between January 2013 and December 2016. Demographic data, vancomycin data (indication, dosing, steady-state SVCs, and time to reach goal SVC), and adverse-effect data (infusion reactions and serum creatinine level) were collected.

RESULTS

Of the 240 patients included, 76 had a goal SVC of 10 to 15 µg/mL and 164 had a goal of 15 to 20 µg/mL. The dose of CIV required to reach an SVC of 10 to 15 µg/mL in the youngest age group was 48.4 mg/kg per day versus 45.6 and 39.4 mg/kg per day in the older age groups (P < .005). The 2 younger age groups of patients with a goal SVC of 15 to 20 µg/mL required 50.2 and 50.6 mg/kg per day, respectively, whereas patients aged ≥8 years required 44.7 mg/kg per day (P = .008). One patient experienced renal injury, and 1 experienced renal failure.

CONCLUSIONS

CIV is an effective method for attaining a therapeutic SVC in pediatric patients. Patients <8 years of age require higher dosing than older pediatric patients to reach the goal SVCs of 10 to 15 and 15 to 20 µg/mL.

Continuous-Infusion Vancomycin in Neonates: Assessment of a Dosing Regimen and Therapeutic Proposal

Introduction: Vancomycin remains the reference antibiotic in neonates for care-related infections caused by ß-lactam-resistant Gram-positive bacteria. Achieving the optimal serum vancomycin level is challenging because of high inter-individual variability and the drug's narrow therapeutic window. Continuous infusion might offer pharmacokinetic and practical advantages, but we lack consensus on the dosing regimen. The aim was to determine the proportion of neonates achieving an optimal therapeutic vancomycin level at the first vancomycin concentration assay and which dosing regimen is the most suitable for neonates. Methods: All neonates receiving continuous-infusion vancomycin (loading dose 15 mg/kg and maintenance dose 30 mg/kg/d) in a neonatal intensive care unit were retrospectively analyzed. The proportion of neonates reaching the target serum vancomycin level was calculated. After reviewing the literature to identify all published articles proposing a dosing regimen for continuous-infusion vancomycin for neonates, regimens were theoretically applied to our population by using maintenance doses according to covariate(s) proposed in the original publication. Results: Between January 2013 and December 2014, 75 neonates received 91 vancomycin courses by continuous infusion. Median gestational age, birth weight, and postnatal age were 27 weeks (interquartile range 26-30.5), 815 g (685-1,240), and 15 days (9-33). At the first assay, only 28/91 (30.8%) courses resulted in vancomycin levels between 20 and 30 mg/L (target level), 23/91 (25.3%) >30 mg/L and 40/91 (43.9%) <20 mg/L. We applied six published dosing regimens to our patients. One of these dosing regimens based on corrected gestational age (CGA) and serum creatinine level (SCR) would have allowed us to prescribe lower doses to neonates with high vancomycin levels and higher doses to neonates with low levels. Conclusions: A simplified dosing regimen of continuous-infusion vancomycin did not achieve therapeutic ranges in neonates; a patient-tailored dosing regimen taking into account CGA and SCR level or an individualized pharmacokinetic model can help to anticipate the inter-individual variability in neonates and would have been more suitable.

Vancomycin Dosing and Monitoring: Critical Evaluation of the Current Practice

After more than six decades of its use as the mainstay antibiotic for the treatment of multidrug-resistant Gram-positive bacterial infections, dosing and monitoring of vancomycin therapy have not been optimized. The current vancomycin therapeutic guidelines recommend empiric doses of 15-20 mg/kg administered by intermittent infusion every 8-12 h in patients with normal kidney function. Additionally, the guidelines recommend trough concentration of 15-20 mg/L as a therapeutic goal for adult patients with severe infections. This review critically discusses the current guidelines considering the basic pharmacokinetics and pharmacodynamics of vancomycin and the recent published reports from clinical studies. More in-depth discussion will be focused on (1) providing evidence of advantages of administering vancomycin by continuous infusion compared to intermittent infusion; (2) revising the current practice of trough-only monitoring versus the area under concentration-time curve (AUC); and (3) assessing the current practice of weight-based dosing versus AUC-based dosing. Using the gathered information presented in this paper, two user-friendly and scientifically based dosing strategies are proposed to improve the efficiency of vancomycin dosing while avoiding the risk of nephrotoxicity and minimizing the cost of therapeutic drug monitoring.

Optimal infusion rate in antimicrobial therapy explosion of evidence in the last five years

Background

Sporadic studies in antimicrobial therapy have evaluated the effects of infusion rates on therapeutic and economic outcomes, and new findings may challenge the regular infusion regimen.

Methods

Focusing on studies comparing the outcomes of different infusion regimens, the relevant literature was identified by searching PubMed, Web of Science, and Scopus from January 1, 2013 to March 1, 2018. Papers were finally chosen using a PRISMA flowchart.

Results

Antimicrobials with the superiority of prolonged infusion to standard infusion in terms of efficacy and safety include meropenem, doripenem, imipenem, cefepime, ceftazidime, piperacillin/tazobactam, linezolid, and vancomycin. The strategy of concomitantly reducing total daily dose and prolonging infusion time may cause treatment failure (eg, imipenem). Extended infusion of piperacillin/tazobactam has pharmacoeconomic advantage over standard infusion. Prolonged infusion of voriconazole is inferior to standard infusion because of lower efficacy caused by pharmacokinetic changes. Comparable outcomes following standard infusion and continuous infusion were observed with norvancomycin and nafcillin. Factors determining whether prolonged infusion has a benefit over standard infusion include MIC of bacterial pathogens, bacterial density, diagnosis, disease severity, total daily dose, and renal function.

Conclusion

To maximally preserve the effectiveness of current antimicrobials, effective interventions should be implemented to enhance the application of optimal infusion strategies. For reducing nephrotoxicity, prolonged infusion of meropenem is better than conventional infusion in neonates with Gram-negative late-onset sepsis, and continuous infusion of vancomycin is superior to intermittent infusion. For increasing efficacy, prolonged or continuous infusion of time-dependent antimicrobials (eg, meropenem, doripenem, imipenem, cefepime, ceftazidime, piperacillin/tazobactam, linezolid, and vancomycin) is an optimal choice. Nevertheless, such advantages may only be demonstrated in special clinical circumstances and special populations (eg, patients with a sequential organ failure assessment (SOFA) score≥9, respiratory tract infections, urinary or intra-abdominal infections, or infections caused by less susceptible pathogens would benefit from prolonged infusion of piperacillin/tazobactam).

Antimicrobial Properties and Osteogenicity of Vancomycin-Loaded Synthetic Scaffolds Obtained by Supercritical Foaming

Advanced porous synthetic scaffolds are particularly suitable for regeneration of damaged tissues, but there is the risk of infections due to the colonization of microorganisms, forming biofilms. Supercritical foaming is an attractive processing method to prepare bone scaffolds, regulating simultaneously the porosity and loading of bioactive compounds without loss of activity. In this work, scaffolds made of poly-ε-caprolactone (50 kDa), containing chitosan and an antimicrobial agent (vancomycin), were processed by supercritical CO₂ foaming for bone regeneration purposes. The obtained scaffolds showed a suitable combination of morphological (porosity, pore size distribution, and interconnectivity), time-dependent in vitro vancomycin release behavior and biological properties (cell viability and proliferation, osteodifferentiation, and tissue-scaffold integration). The scaffolds sustained vancomycin release for more than 2 weeks. Finally, the antimicrobial activity of the scaffolds was tested against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria after 24 h of incubation with full growth inhibition for S. aureus.

Compatibility of Ceftazidime-Avibactam, Ceftolozane-Tazobactam, and Piperacillin-Tazobactam with Vancomycin in Dextrose 5% in Water

Objectives: The compatibility of vancomycin with existing and novel β-lactam/β-lactamase inhibitors at clinically relevant concentrations in 5% dextrose in water has not been fully explored to date. Methods: Vancomycin concentrations tested ranged from 5 to 20 mg/mL. Ceftazidime-avibactam was tested at 8, 20, and 40 mg/mL, ceftolozane-tazobactam at 15 mg/mL, and piperacillin-tazobactam at 28 mg/mL. Compatibility of drug admixtures were tested via both simulated and actual y-site infusion. For the simulated y-site compatibility assessment, 1:1 mixtures of each respective drug were analyzed over 24 hours. Actual y-site infusion followed a 4-hour extended-infusion protocol, with aliquots tested hourly for 4 hours. At all time points, the compatibility of each admixture was determined using 6 different methods: visual, microscopic, Tyndall beam, nephelometric, pH, and microbiologic bioassay assessment. If any admixture failed any one of these 6 assays, it was considered incompatible. Any combination deemed incompatible was filtered through a 0.22 μm filter and reanalyzed to assess impact of particle size. Results: There were no differences in compatibility categorizations between simulated and actual y-site infusion. There were no changes in compatibility over the time course of any experiment. Ceftazidime-avibactam at 8 mg/mL was incompatible with vancomycin at 5 mg/mL. The maximum compatible vancomycin concentrations were 5 mg/mL and 10 mg/mL with 20 and 40 mg/mL of ceftazidime-avibactam, respectively. Ceftolozane-tazobactam 15 mg/mL was compatible with vancomycin concentrations up to 10 mg/mL. The maximum compatible vancomycin concentration with piperacillin-tazobactam 28 mg/mL was 5 mg/mL. None of the β-lactam/β-lactamase inhibitors tested were compatible with 15 or 20 mg/mL of vancomycin. None of the admixtures considered incompatible by other methods displayed any decrease in antimicrobial activity as assessed by bioassay. After filtration, all admixtures originally deemed incompatible maintained their visual turbidity and microscopic particulate matter. Conclusions: Ceftazidime-avibactam prepared at the lowest concentration recommended in the package insert is incompatible with vancomycin. Ceftolozane-tazobactam did not display incompatibility until vancomycin concentrations above 10 mg/mL were tested. Piperacillin-tazobactam at a typical extended-infusion concentration is compatible with vancomycin in D5W. To our knowledge, this is the first study to assess compatibility of antibiotic admixtures via direct measurement of antimicrobial activity. The lack of any decrement in antibacterial activity of any apparently incompatible admixture and maintenance of incompatibility after passage through a 0.22 μm filter may suggest a lack of clinically relevant adverse effects when co-administered. Future compatibility studies should incorporate appropriate methods to accurately assess both efficacy and safety of co-administered drug products.

Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement

OBJECTIVES

Thermal stability is a key property in determining the suitability of an antibiotic agent for local application in the treatment of orthopaedic infections. Despite the fact that long-term therapy is a stated goal of novel local delivery carriers, data describing thermal stability over a long period are scarce, and studies that avoid interference from specific carrier materials are absent from the orthopaedic literature.

METHODS

In this study, a total of 38 frequently used antibiotic agents were maintained at 37°C in saline solution, and degradation and antibacterial activity assessed over six weeks. The impact of an initial supplementary heat exposure mimicking exothermically curing bone cement was also tested as this material is commonly used as a local delivery vehicle. Antibiotic degradation was assessed by liquid chromatography coupled to mass spectrometry, or by immunoassays, as appropriate. Antibacterial activity over time was determined by the Kirby-Bauer disk diffusion assay.

RESULTS

The heat exposure mimicking curing bone cement had minimal effect on stability for most antibiotics, except for gentamicin which experienced approximately 25% degradation as measured by immunoassay. Beta-lactam antibiotics were found to degrade quite rapidly at 37°C regardless of whether there was an initial heat exposure. Excellent long-term stability was observed for aminoglycosides, glycopeptides, tetracyclines and quinolones under both conditions.

CONCLUSIONS

This study provides a valuable dataset for orthopaedic surgeons considering local application of antibiotics, and for material scientists looking to develop next-generation controlled or extended-release antibiotic carriers.Cite this article: E. Samara, T. F. Moriarty, L. A. Decosterd, R. G. Richards, E. Gautier, P. Wahl. Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement. Bone Joint J 2017;6:296-306. DOI: 10.1302/2046-3758.65.BJR-2017-0276.R1.

Vancomycin-loaded nanobubbles: A new platform for controlled antibiotic delivery against methicillin-resistant Staphylococcus aureus infections

Vancomycin (Vm) currently represents the gold standard against methicillin-resistant Staphylococcus aureus (MRSA) infections. However, it is associated with low oral bioavailability, formulation stability issues, and severe side effects upon systemic administration. These drawbacks could be overcome by Vm topical administration if properly encapsulated in a nanocarrier. Intriguingly, nanobubbles (NBs) are responsive to physical external stimuli such as ultrasound (US), promoting drug delivery. In this work, perfluoropentane (PFP)-cored NBs were loaded with Vm by coupling to the outer dextran sulfate shell. Vm-loaded NBs (VmLNBs) displayed ∼300nm sizes, anionic surfaces and good drug encapsulation efficiency. In vitro, VmLNBs showed prolonged drug release kinetics, not accompanied by cytotoxicity on human keratinocytes. Interestingly, VmLNBs were generally more effective than Vm alone in MRSA killing, with VmLNB antibacterial activity being more sustained over time as a result of prolonged drug release profile. Besides, VmLNBs were not internalized by staphylococci, opposite to Vm solution. Further US association promoted drug delivery from VmLNBs through an in vitro model of porcine skin. Taken together, these results support the hypothesis that proper Vm encapsulation in US-responsive NBs might be a promising strategy for the topical treatment of MRSA wound infections.

Optimizing the Clinical Use of Vancomycin

The increasing number of infections produced by beta-lactam-resistant Gram-positive bacteria and the morbidity secondary to these infections make it necessary to optimize the use of vancomycin. In 2009, the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, and the Society of Infectious Disease Pharmacists published specific guidelines about vancomycin dosage and monitoring. However, these guidelines have not been updated in the past 6 years. This review analyzes the new available information about vancomycin published in recent years regarding pharmacokinetics and pharmacodynamics, serum concentration monitoring, and optimal vancomycin dosing in special situations (obese people, burn patients, renal replacement therapy, among others). Vancomycin efficacy is linked to a correct dosage which should aim to reach an area under the curve (AUC)/MIC ratio of ≥400; serum trough levels of 15 to 20 mg/liter are considered a surrogate marker of an AUC/MIC ratio of ≥400 for a MIC of ≤1 mg/liter. For Staphylococcus aureus strains presenting with a MIC >1 mg/liter, an alternative agent should be considered. Vancomycin doses must be adjusted according to body weight and the plasma trough levels of the drug. Nephrotoxicity has been associated with target vancomycin trough levels above 15 mg/liter. Continuous infusion is an option, especially for patients at high risk of renal impairment or unstable vancomycin clearance. In such cases, vancomycin plasma steady-state level and creatinine monitoring are strongly indicated.

Preparing and administering injectable antibiotics: How to avoid playing God

The emergence of bacterial resistance and the lack of new antibiotics in the pipeline represent a public health priority. Maximizing the quality of antibiotic prescriptions is therefore of major importance in terms of adequate preparation and administration modalities. Adequate preparation prevents the inactivation of antibiotics and is a prerequisite to maximizing their efficacy (taking into account the pharmacokinetic/pharmacodynamic relationship) and to minimizing their toxicity. Many antibiotic guidelines address the choice of drugs and treatment duration but none of them exclusively address preparation and administration modalities. These guidelines are based on the available literature and offer essential data for a proper antibiotic preparation and administration by physicians and nurses. They may lead to a better efficacy and to a reduced antibiotic resistance. Such guidelines also contribute to a proper use of drugs and improve the interaction between inpatient and outpatient care for a better overall management of patients.

Compatibility of cefepime and vancomycin during simulated Y-site administration of prolonged infusion

PURPOSE

The physical and chemical compatibility of cefepime and vancomycin at concentrations typically used in prolonged-infusion cefepime infusions was assessed.

METHODS

Samples from a typical Y-site configuration of standard-infusion vancomycin and prolonged-infusion cefepime were collected at various time points during the simulated 4-hour infusion. Samples were analyzed by visual inspection, spectrophotometry, and high-performance liquid chromatography (HPLC). Infusion antibiotics were reconstituted in pairwise combinations of 0.9% sodium chloride injection and 5% dextrose injection to determine the effects of solvent selection on stability. Infusion simulations were performed in triplicate without light protection under fluorescent lighting at room temperature (22.5 °C). Experimental replicates were not run simultaneously but on sequential days due to the considerable time (~12 hours) required to analyze samples obtained from a single infusion simulation and the known time-dependent instability of reconstituted cefepime beyond 24 hours. Physical stability was assessed visually for evidence of particulate formation, haze, precipitation, color change, and gas evolution. Samples were also assessed spectrophotometrically at 600 nm at the time of collection and 24 hours after collection.

RESULTS

Cefepime was compatible with vancomycin at the concentrations tested. The solvent selected (0.9% sodium chloride or 5% dextrose) to reconstitute either antibiotic had no impact on compatibility. Solutions were indistinguishable from positive and negative controls (heat-degraded cefepime and freshly reconstituted cefepime, respectively) at all time points assessed in terms of visual clarity, spectrophotometric absorbance, and HPLC recovery.

CONCLUSION

Cefepime and vancomycin were physically and chemically compatible during simulated Y-site administration of prolonged-infusion cefepime.

How to use vancomycin optimally in neonates: remaining questions

In neonates, vancomycin, a narrow-spectrum antibiotic, is the first choice of treatment of late-onset sepsis predominantly caused by Gram-positive bacteria (coagulase-negative staphylococci and enterococci). Although it has been used for >50 years, prescribing the right dose and dosing regimen remains a challenge in neonatal intensive care units for many reasons including high pharmacokinetic variability, increase in the minimal inhibition concentration against staphylococci, lack of consensus on dosing regimen and way of administration (continuous or intermittent), duration of treatment, use of therapeutic drug monitoring, limited data on short- and long-term toxicity, risk of mutant selection and errors of administration linked to concentrated formulations. This article highlights and discusses future research directions, with specific attention given to dosing optimization of vancomycin, including the advantages of modeling and simulation approaches.

Endothelial Cell Toxicity of Vancomycin Infusion Combined with Other Antibiotics

French guidelines recommend central intravenous (i.v.) infusion for high concentrations of vancomycin, but peripheral intravenous (p.i.v.) infusion is often preferred in intensive care units. Vancomycin infusion has been implicated in cases of phlebitis, with endothelial toxicity depending on the drug concentration and the duration of the infusion. Vancomycin is frequently infused in combination with other i.v. antibiotics through the same administrative Y site, but the local toxicity of such combinations has been poorly evaluated. Such an assessment could improve vancomycin infusion procedures in hospitals. Human umbilical vein endothelial cells (HUVEC) were challenged with clinical doses of vancomycin over 24 h with or without other i.v. antibiotics. Cell death was measured with the alamarBlue test. We observed an excess cellular death rate without any synergistic effect but dependent on the numbers of combined infusions when vancomycin and erythromycin or gentamicin were infused through the same Y site. Incompatibility between vancomycin and piperacillin-tazobactam was not observed in our study, and rinsing the cells between the two antibiotic infusions did not reduce endothelial toxicity. No endothelial toxicity of imipenem-cilastatin was observed when combined with vancomycin. p.i.v. vancomycin infusion in combination with other medications requires new recommendations to prevent phlebitis, including limiting coinfusion on the same line, reducing the infusion rate, and choosing an intermittent infusion method. Further studies need to be carried out to explore other drug combinations in long-term vancomycin p.i.v. therapy so as to gain insight into the mechanisms of drug incompatibility under multidrug infusion conditions.

The pharmacokinetic/pharmacodynamic rationale for administering vancomycin via continuous infusion

WHAT IS KNOWN AND OBJECTIVE

Vancomycin is administered via intermittent infusion (II) almost exclusively in the United States, whereas continuous infusion (CI) dosing methods are used regularly in many European countries. The purpose of this literature analysis is to review current evidence regarding the advantages and disadvantages of CI vancomycin in relation to II, based on the pharmacokinetic and pharmacodynamic aspects of dosing and monitoring therapy, and to identify current practices of CI vancomycin dosing.

METHODS

Medline, Cochrane and GoogleScholar databases were searched using vancomycin as a MeSH term, along with continuous and infusion in all fields, which identified 136 citations. A second search added the terms intermittent and survey, producing nine additional articles. All articles that reported an assessment of CI or II vancomycin administration in adult patients, based on clinical, pharmacokinetic, cost or monitoring considerations, were identified. A total of 43 publications were determined to be suitable for final analysis and possible inclusion in the report.

RESULTS AND DISCUSSION

A meta-analysis of six studies concluded that CI vancomycin was associated with a lower relative risk of kidney injury than II therapy, although other studies reported equivocal findings. The results of several clinical studies suggest that CI vancomycin produces clinical outcomes that are comparable to II. Current vancomycin consensus guidelines promote aggressive dosing to achieve trough levels of 10-15 or 15-20 mg/L, but also include recommendations to target a daily area under the curve (AUC24 ) to minimum inhibitory concentration (MIC) ratio of at least 400. Because vancomycin is a non-concentration-dependent antibiotic, it might be more prudent to monitor steady-state serum concentrations (Css ) during a CI rather than trough concentrations during II, due to the questionable correlation between measured trough concentration and AUC. From a pharmacokinetic/pharmacodynamic perspective, vancomycin dosing and monitoring practices associated with CI offer potentially greater reliability than II. A major disadvantage of CI involves the possibility of having to intravenously co-administer another drug that might not be compatible with vancomycin.

WHAT IS NEW AND CONCLUSION

Continuous infusion vancomycin therapy offers the advantage of Css monitoring, thus avoiding the variabilities associated with the timing of trough levels. Current CI practices include a loading dose of 15-20 mg/kg followed by an infusion of 10-40 mg/kg/day based on the patient's renal function, with a target Css of about 20-30 mg/L. An alternative approach to weight-based (mg/kg) CI dosing is to calculate the dose from an estimation of the patient's vancomycin clearance (in L/h), derived from creatinine clearance (CrCl) via the equation (CrCl∙0·041) + 0·22. The daily dose is then determined by multiplying vancomycin clearance (in L/h) by the desired AUC24 . A new CI vancomycin dosing chart includes clearance-based dosing recommendations for Css values ranging from 17·5 to 27·5 mg/L or AUC24 values ranging from 420 to 660 mg h/L. Although sufficient data already exist to support the use of CI vancomycin as a reasonable therapeutic alternative to II, there is still much to learn about administering the drug in this fashion.

Influence of vancomycin infusion methods on endothelial cell toxicity

Peripheral intravenous therapy is frequently used in routine hospital practice and, due to various factors, its most common side effect is phlebitis. The infusion of vancomycin is particularly associated with phlebitis despite its widespread use. French guidelines recommend central intravenous infusion for high concentrations of vancomycin, but peripheral intravenous therapy is often preferred in intensive care units. Methods of vancomycin infusion are either intermittent infusion or continuous infusion. A comparison of these methods under in vitro conditions simulating clinical use could result in better infusion efficacy. Human umbilical vein endothelial cells (HUVECs) were therefore challenged with clinical doses of vancomycin over a 24- to 72-h period using these infusion methods. Cell death was measured with the alamarBlue test. Concentration-dependent and time-dependent vancomycin toxicity on HUVECs was noted with a 50% lethal dose at 5 mg/ml after 24 h, reaching 2.5 mg/ml after 72 h of infusion, simulating long-term infusion. This toxicity does not seem to be induced by acidic pH. In comparing infusion methods, we observed that continuous infusion induced greater cell toxicity than intermittent infusion at doses higher than 1 g/day. The increasing use of vancomycin means that new guidelines are required to avoid phlebitis. If peripheral intravenous therapy is used to reduce infusion time, along with intermittent infusion, vein irritation and localized phlebitis may be reduced. Further studies have to be carried out to explore the causes of vancomycin endothelial toxicity.

Design and prospective validation of a dosing instrument for continuous infusion of vancomycin: a within-population approach

INTRODUCTION

The clinical application of continuous infusion (CoI) of vancomycin has gained interest in recent years. Since no international guidelines on initial dosing of vancomycin CoI exist, there is a need for methods to facilitate the switch from intermittent to continuous vancomycin dosing algorithms in clinically infected populations. Therefore, the aim of this study was to design and validate an a priori dosing schedule for CoI of vancomycin in clinical practice.

METHODS

A dosing table for CoI of vancomycin based on estimated glomerular filtration rate (eGFR) was developed by simulation of continuous infusion of vancomycin using pharmacokinetic (PK) software and a PK population model designed from historical within-population data in intermittently dosed patients. The target range for the first vancomycin serum concentrations drawn approximately 24 h after start of infusion' (C24) was set at 15-20 mg/L corresponding with an area under the curve (AUC) of at least 350 mg·h·L(-1). The performance of the dosing schedule was primarily assessed by describing the percentages of patients attaining the predefined target.

RESULTS

An eGFR-derived dosing schedule for CoI of vancomycin was established and implemented in clinical practice. Prospective assessment in 35 general ward and 45 intensive care unit patients showed that the C24 target was reached in 69 and 63 % and the AUC target was attained in 80 and 72 % of patients, respectively.

CONCLUSIONS

An easy method to design and validate an eGFR-derived dosing algorithm for the continuous infusion of vancomycin to switch from intermittent to continuous dosing of vancomycin was developed.

Neonatal vancomycin continuous infusion: still a confusion?

BACKGROUND

Continuous infusions of vancomycin over 24 hours have been shown in adults to reduce drug toxicity, lower treatment costs and require fewer blood samples for therapeutic drug monitoring. They may also improve clinical outcome through earlier attainment of target drug concentrations. In neonates, there is no consensus on vancomycin dosing. We reviewed the literature to assess the evidence for vancomycin dosing regimens for continuous infusion in neonates.

METHODS

Medline and Embase were searched for studies about continuous vancomycin dosing regimens in neonates that reported serum drug concentrations. The search identified 469 articles, of which 5 were relevant.

RESULTS

Five prospective studies were included; 2 studies used non-linear mixed effects modeling. Vancomycin was administered with parenteral nutrition or 5% dextrose. Target serum concentrations varied (range: 10-30 mg/L). Four studies used loading doses before continuous infusion; only 1 documented achievement of therapeutic concentrations after the load. The time to a therapeutic concentration was not reported for the other studies. Attainment of target concentrations ranged from 56% to 89% of measurements. Only 1 study compared intermittent to continuous infusions, reporting higher attainment of target concentrations with continuous dosing (82% vs. 46%). No adverse effects were reported, although 3 neonates developed a reversible raised serum creatinine in the setting of septicemia.

CONCLUSION

Continuous infusions of vancomycin in neonates are well tolerated, require less blood sampling and may result in improved attainment of target concentrations. Further prospective studies are needed in this population.

Effects of antibiotic physicochemical properties on their release kinetics from biodegradable polymer microparticles

PURPOSE

This study investigated the effects of the physicochemical properties of antibiotics on the morphology, loading efficiency, size, release kinetics, and antibiotic efficacy of loaded poly(DL-lactic-co-glycolic acid) (PLGA) microparticles (MPs) at different loading percentages.

METHODS

Cefazolin, ciprofloxacin, clindamycin, colistin, doxycycline, and vancomycin were loaded at 10 and 20 wt% into PLGA MPs using a water-in-oil-in water double emulsion fabrication protocol. Microparticle morphology, size, loading efficiency, release kinetics, and antibiotic efficacy were assessed.

RESULTS

The results from this study demonstrate that the chemical nature of loaded antibiotics, especially charge and molecular weight, influence the incorporation into and release of antibiotics from PLGA MPs. Drugs with molecular weights less than 600 Da displayed biphasic release while those with molecular weights greater than 1,000 Da displayed triphasic release kinetics. Large molecular weight drugs also had a longer delay before release than smaller molecular weight drugs. The negatively charged antibiotic cefazolin had lower loading efficiency than positively charged antibiotics. Microparticle size appeared to be mainly controlled by fabrication parameters, and partition and solubility coefficients did not appear to have an obvious effect on loading efficiency or release. Released antibiotics maintained their efficacy against susceptible strains over the duration of release. Duration of release varied between 17 and 49 days based on the type of antibiotic loaded.

CONCLUSIONS

The data from this study indicate that the chemical nature of antibiotics affects properties of antibiotic-loaded PLGA MPs and allows for general prediction of loading and release kinetics.