Selecting antibacterials for outpatient parenteral antimicrobial therapy : pharmacokinetic-pharmacodynamic considerations

Systematic review of the stability of antimicrobial agents in elastomeric devices for outpatient parenteral antimicrobial therapy services based on NHS Yellow Cover Document standards

BACKGROUND

In order to use aseptically prepared elastomeric infusers, outpatient parenteral antimicrobial therapy (OPAT) services require extended stability data for antimicrobial agents to assign a product shelf-life. In the UK, the relevant standards for stability testing and shelf-life assignment are published in 'A Standard Protocol for Deriving and Assessment of Stability-Part 1 (Aseptic Preparations-Small Molecules), commonly called the Yellow Covered Document (YCD). A previous systematic review published in 2017 failed to identify data on the stability of antimicrobials in elastomeric devices for OPAT services that met YCD requirements in force at the time. The aim of this review was to update that search, following a subsequent change to YCD requirements in 2017 and 2019 and expand that dataset to identify progress made in providing assurance about the stability of antimicrobial agents for OPAT services.

METHODS

Searches were undertaken for papers relating to extended stability of antimicrobials. Citations were included when antimicrobial shelf-life was assessed using a stability-indicating method and considered a period of storage, either refrigerated or at room temperature, followed by in-use testing at a temperature at or above 32°C.

RESULTS

Of 267 initial citations, six met the inclusion criteria and underwent full text review for data extraction. Included antimicrobials were cefazolin, ceftazidime, piperacillin/tazobactam, flucloxacillin and ceftolozane/tazobactam. Of these, only flucloxacillin and piperacillin demonstrated YCD compliant stability over the 24-hour infusion period while cefazolin, ceftazidime and ceftolozane/tazobactam could be infused over 12-hour period.

CONCLUSIONS

Contrary to the position found in 2017 review, high-quality data are now available to support the use of a number of antimicrobial agents in extended infusion in elastomeric devices for OPAT services. There is a need to expand the dataset, as well as developing international consensus on the ideal parameters for stability assessment of such infusions in elastomeric devices.

Variability in Biological Activities of Satureja montana Subsp. montana and Subsp. variegata Based on Different Extraction Methods

Winter savory (Satureja montana L.) is a well-known spice and medicinal plant with a wide range of activities and applications. Two subspecies of S. montana, subsp. montana and subsp. variegata, were used for the preparation of seven different extracts: steam distillation (essential oil (EO) and hydrolate (HY)), subcritical water (SWE), ultrasound-assisted (UAE-MeOH and UAE-H₂O), and microwave-assisted (MAE-MeOH and MAE-H₂O) extraction. The obtained EOs, HYs, and extracts were used for an in vitro evaluation of the antioxidant activity (DPPH, ABTS, reducing power, and superoxide anion methods) and in vitro antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Salmonella Typhimurium, Saccharomyces cerevisiae, and Candida albicans. The antimicrobial screening was conducted using disk-diffusion assessment, minimal inhibitory concentration, time–kill kinetics modeling, and pharmacodynamic study of the biocide effect. The total phenolic content (TPC) was highest in EO, followed by SWE, MAE, and UAE, and the lowest was in HY. The highest antimicrobial activity shows EO and SWE for both varieties, while different UAE and MAE extracts have not exhibited antimicrobial activity. The natural antimicrobials in the S. montana extract samples obtained by green extraction methods, indicated the possibility of ecologically and economically better solutions for future in vivo application of the selected plant subspecies.

Outpatient therapy with piperacillin/tazobactam using elastomeric pumps in patients with Pseudomonas aeruginosa infection

The aim of this study was to evaluate the efficacy and safety of outpatient antimicrobial therapy with piperacillin-tazobactam in continuous infusion using elastomeric pumps and to evaluate the economic impact compared with conventional hospital treatment in patients with Pseudomonas aeruginosa (PA) infections. This is an observational study. Patients with PA infection treated with continuous piperacillin-tazobactam infusion using elastomeric pumps in our hospital between January 2015 and December 2017 were included. Primary outcomes were mortality during antibiotic treatment and mortality at 30 days. Secondary outcomes were reinfection or relapse at 30 days and clinical cure rate. The cost of each episode was compared with theoretical cost of the same treatment using conventional hospitalization. 35 patients were included. One patient (2.9%) died during the treatment. Overall 30-day mortality was 5.7%. No death was related to infection by PA. One patient (2.9%) had a reinfection at 30 days. Cure was achieved in 93% of patients at the end of treatment. There were no severe complications related to elastomeric pumps. Treatment cost with outpatient antimicrobial therapy was 67% lower than theoretical cost with conventional hospital treatment. Oupatient antimicrobial therapy with piperacillin-tazobactam in continuous infusion using elastomeric pumps in patients with PA infections is safe and effective with lower costs.

Practical Considerations in Sepsis Resuscitation

BACKGROUND

Sepsis is a common condition managed in the emergency department, and the majority of patients respond to resuscitation measures, including antibiotics and i.v. fluids. However, a proportion of patients will fail to respond to standard treatment.

OBJECTIVE

This review elucidates practical considerations for management of sepsis in patients who fail to respond to standard treatment.

DISCUSSION

Early goal-directed therapy revolutionized sepsis management. However, there is a paucity of literature that provides a well-defined treatment algorithm for patients who fail to improve with therapy. Refractory shock can be defined as continued patient hemodynamic instability (mean arterial pressure, ≤ 65 mm Hg, lactate ≥ 4 mmol/L, altered mental status) after adequate fluid loading (at least 30 mL/kg i.v.), the use of two vasopressors (with one as norepinephrine), and provision of antibiotics. When a lack of improvement is evident in the early stages of resuscitation, systematically considering source control, appropriate volume resuscitation, adequate antimicrobial coverage, vasopressor selection, presence of metabolic pathology, and complications of resuscitation, such as abdominal compartment syndrome and respiratory failure, allow emergency physicians to address the entire clinical scenario.

CONCLUSIONS

The care of sepsis has experienced many changes in recent years. Care of the patient with sepsis who is not responding appropriately to initial resuscitation is troublesome for emergency physicians. This review provides practical considerations for resuscitation of the patient with septic shock. When a septic patient is refractory to standard therapy, systematically evaluating the patient and clinical course may lead to improved outcomes.

Optimization of a model of out-of-hospital antibiotic therapy (OPAT) in a Belgian university hospital resulting in a proposal for national implementation

OBJECTIVES

Some infections require prolonged parenteral antimicrobial therapy, which can be continued in an outpatient setting. The Ghent University Hospital has 15 years of experience with Outpatient Parenteral Antimicrobial Therapy (OPAT) in the home setting of the patient.

METHODS

Multidisciplinary critical approach through identification of areas for improvement with the existing OPAT process within the Ghent University Hospital. Existing literature and guidelines were used as references. An improved model is proposed for implementation.

RESULTS

Several challenges and barriers were identified, including regulatory obstacles for OPAT in Belgium, such as lack of uniformity in ambulatory reimbursement of parenteral antimicrobials. There is no financial incentive for the patient with OPAT, as costs for the patient of outpatient therapy can be higher as compared with hospitalization. Other barriers include delayed approval of the certificate for reimbursement, low availability of medicines in the community pharmacies and limited knowledge of the medical devices for administration in ambulatory setting. All critical steps in the revised OPAT program are summarized in a flowchart with a checklist for all stakeholders. Firstly, a list with specific criteria to include patients in an OPAT program is provided. Secondly, the Multidisciplinary Infection Team received a formal mandate to review all eligible OPAT patients. In order to select the most appropriate catheter, a decision tree was developed and standardized packages with medical devices were developed. Thirdly, patients receive oral and written information about the treatment with practical and financial implications. Fourthly, information is provided toward the general practitioners, community pharmacist and home care nurse.

CONCLUSION

Standardization of the OPAT program aims at improving quality and safety of intravenous antimicrobial therapy in the home setting.

The pharmacokinetic interaction between levofloxacin and sunitinib

BACKGROUND

The aim of this study was to evaluate the impact of sunitinib on pharmacokinetics of levofloxacin. The previous study proved that levofloxacin co-administered with sunitib changes the following pharmacokinetic parameters i.e. Cmax and AUC for both sunitinib and SU012662 (sunitinib metabolite). We will also investigate if the limited sample strategy can be applied for levofloxacin.

METHODS

Rabbits were divided into two groups. In both groups there were six animals. In the control group levofloxacin was administered and in investigated group levofloxacin and sunitinib were co-administered. The dose of levofloxacin was 20mg/kg and the dose of sunitinib was 25mg. The concentration in plasma was determined by HPLC-FLD. The pharmacokinetic parameters were evaluated by WinNonLin software. The results were evaluated by the following statistical tests: Shapiro-Wilk, t-Student and Mann-Whitney test.

RESULTS

Pharmacokinetics of levofloxacin obeys the two-compartment model. Sunitinib influences the following pharmacokinetic parameters of levofloxacin: half-life, elimination constant and volume of distribution. Statistical analysis proved that there is a correlation between AUC and the following five time-points: 0.25 h, 4h, 6h, 10h and 12h.

CONCLUSIONS

The study proved that there is a potential pharmacokinetic interaction between sunitinib and levofloxacin. The statistical analysis proved that the limited sample strategy can be applied for levofloxacin.

A national survey of infectious disease practitioners on their use of outpatient parenteral antimicrobial therapy (OPAT)

BACKGROUND

The use of outpatient parenteral antimicrobial therapy (OPAT) is standard medical practice; however, significant heterogeneity in practice exists. We hypothesized that formal OPAT programs are associated with increased physician participation in patient safety activities.

METHODS

United States Infectious Disease (ID) physicians were contacted and asked to participate in an electronic survey from April through June 2012. Data were analyzed using SPSS version 20.

RESULTS

In all, 3718 physicians were contacted and 316 (8.5%) responded. Respondents practice in 47 states; the majority (79%) practice adult ID, 11% pediatric ID, 10% a combination of the two. Sixty percent reported that ID consultation was not mandatory before OPAT, and 75% of these respondents thought it should be compulsory. The most common indications were osteomyelitis, prosthetic joint infections, and endocarditis, and the most common antibiotics were vancomycin, ceftriaxone, and ertapenem. Most respondents (59%) discharge patients with OPAT weekly, and have a median number of 11 OPAT patients (95% confidence interval (CI) 8.5-13.4). Half of respondents have a formal OPAT program. Fifty-two percent report no systematic method of communication between inpatient and outpatient physicians when patients are discharged with OPAT, 49% have no systematic method of lab tracking, and 34% have no method of ensuring patient adherence to clinic visits. All of these patient safety measures were more likely to be present in practice sites with formal OPAT programs (p < 0.001).

CONCLUSIONS

Opportunities exist for improving OPAT monitoring and patient safety. Formal OPAT programs provide the framework for safe and effective care and are to be encouraged.

Emergency department antimicrobial considerations in severe sepsis

Severe sepsis and septic shock are common problems in the emergency department patient population and require expert clinical skill by members of the emergency department team to maximize optimal patient outcomes. Although various guidelines have been developed for the management of these patients, issues around antimicrobial-related considerations in critically ill patients require further evidence-based attention. In this review article, important factors related to patient illness, microorganism, timing of antimicrobial administration, and source control are discussed.

Managing an outpatient parenteral antibiotic therapy team: challenges and solutions

Outpatient parenteral antimicrobial therapy (OPAT) programs should strive to deliver safe, cost effective, and high quality care. One of the keys to developing and sustaining a high quality OPAT program is to understand the common challenges or barriers to OPAT delivery. We review the most common challenges to starting and managing an OPAT program and give practical advice on addressing these issues.

Is generic rifaximin still a poorly absorbed antibiotic? A comparison of branded and generic formulations in healthy volunteers

Rifaximin is an antibiotic, locally acting in the gastrointestinal tract, which may exist in different crystal as well as amorphous forms. The branded rifaximin formulation contains the polymorph rifaximin-α, whose systemic bioavailability is very limited. This study was performed to compare the pharmacokinetics of this formulation with that of a generic product, whose composition in terms of solid state forms of the active pharmaceutical ingredient was found to be different. Two tablets (2×200mg) of branded and generic formulations were given to 24 healthy volunteers of either sex, according to a single-blind, randomized, two-treatment, single-dose, two-period, cross-over design. Plasma and urinary samples were collected at preset times (for 24h or 48h, respectively) after dosing, and assayed for rifaximin concentrations by high-performance liquid chromatography-mass spectrometry. Rifaximin plasma and urine concentration-time profiles showed relevant differences when generic and branded rifaximin were compared. Most pharmacokinetic parameters were significantly higher after administration of generic rifaximin than after rifaximin-α. In particular, the differences for Cmax, AUC and cumulative urinary excretion between the generic formulation and the branded product ranged from 165% to 345%. The few adverse events recorded were not serious and not related to study medications. The results of the present investigation demonstrate different systemic bioavailability of generic and branded formulations of rifaximin. As a consequence, the therapeutic results obtained with rifaximin-α should not be translated sic et simpliciter to the generic formulations of rifaximin, which do not claim containing only rifaximin-α and will display significantly higher systemic absorption in both health and disease.

Antimicrobial treatment of febrile neutropenia: pharmacokinetic-pharmacodynamic considerations

Patients with cancer or hematologic diseases are particularly at risk of infection leading to high morbidity, mortality and costs. Extensive data show that optimization of the administration of antimicrobials according to their pharmacokinetic and pharmacodynamic parameters improves clinical outcome. Evidence is growing that when pharmacokinetic and pharmacodynamic parameters are used to target not only clinical cure but also eradication, the selection resistance is also contained. This is of particular importance in patients with neutropenia in whom increasing rates of drug-resistant Gram-negative bacteria have been reported, particularly Pseudomonas aeruginosa. Based on experimental and clinical studies, pharmacokinetic and pharmacodynamic parameters are discussed in this review for each antibiotic used in febrile neutropenia in order to help physicians improve dosing and optimization of antimicrobial agents.

Outpatient parenteral antimicrobial therapy (OPAT) in the Republic of Ireland: results of a national survey

Outpatient parenteral antimicrobial therapy (OPAT) services are not well developed in the Republic of Ireland. A national programme is being instituted to standardise care. This survey aims to assess the current use of outpatient intravenous antibiotics and to quantify the needs that physicians identify in the development of a national programme. General medical consultant physicians and clinical microbiology consultants were contacted through the Royal College of Physicians of Ireland (RCPI) from April to June 2012. Data were analysed using SPSS version 20. A total of 512 physicians were contacted, of which 55 (10.7 %) responded. The majority, 38/55 (69 %), practice general internal medicine in combination with a medical specialty, 2 (4 %) general internal medicine alone, 8 (15 %) clinical microbiology and 7 (13 %) a medical specialty alone. Of those practising a medical specialty, 12 (27 %) practice infectious diseases. Seventy-four percent reported having discharged patients with intravenous antibiotics; however, 47 % did not have a designated service available. Of those with no service, 100 % identified a need for these resources. Of those responsible for an OPAT service, 56 % had not audited their service. The most common indications were skin and soft tissue infections, osteomyelitis and respiratory tract infection. Flucloxacillin was the most commonly reported antibiotic. Eleven percent responded that they never monitor laboratory studies for patients discharged with intravenous antibiotics. While OPAT services in Ireland are not well developed, patients are being discharged with intravenous antibiotics. This survey underscores the need to develop the national programme to standardise care and ensure patients receive safe and efficient therapy.

Are we ready for an outpatient parenteral antimicrobial therapy bundle? A critical appraisal of the evidence

Healthcare "bundles" have been developed to help providers improve the reliability and delivery of essential healthcare processes. Bundles have been shown to be effective in reducing healthcare-associated infection rates and are increasingly used to ensure the quality of patient care. Outpatient parenteral antimicrobial therapy (OPAT) is now standard medical practice in the treatment of a wide variety of infections. We review 6 components that we believe comprise an OPAT bundle and the evidence supporting each: patient selection, infectious disease consultation, patient/caregiver education, discharge planning, outpatient monitoring/tracking, and OPAT program review. To ensure that patients are receiving optimal care, further program development and outcomes research should target these bundle components to bring the evidence base up to date with current medical practices.

Limited-sampling strategies for anti-infective agents: systematic review

BACKGROUND

Area under the concentration-time curve (AUC) is a pharmacokinetic parameter that represents overall exposure to a drug. For selected anti-infective agents, pharmacokinetic-pharmacodynamic parameters, such as AUC/MIC (where MIC is the minimal inhibitory concentration), have been correlated with outcome in a few studies. A limited-sampling strategy may be used to estimate pharmacokinetic parameters such as AUC, without the frequent, costly, and inconvenient blood sampling that would be required to directly calculate the AUC.

OBJECTIVE

To discuss, by means of a systematic review, the strengths, limitations, and clinical implications of published studies involving a limited-sampling strategy for anti-infective agents and to propose improvements in methodology for future studies.

METHODS

The PubMed and EMBASE databases were searched using the terms "anti-infective agents", "limited sampling", "optimal sampling", "sparse sampling", "AUC monitoring", "abbreviated AUC", "abbreviated sampling", and "Bayesian". The reference lists of retrieved articles were searched manually. Included studies were classified according to modified criteria from the US Preventive Services Task Force.

RESULTS

Twenty studies met the inclusion criteria. Six of the studies (involving didanosine, zidovudine, nevirapine, ciprofloxacin, efavirenz, and nelfinavir) were classified as providing level I evidence, 4 studies (involving vancomycin, didanosine, lamivudine, and lopinavir-ritonavir) provided level II-1 evidence, 2 studies (involving saquinavir and ceftazidime) provided level II-2 evidence, and 8 studies (involving ciprofloxacin, nelfinavir, vancomycin, ceftazidime, ganciclovir, pyrazinamide, meropenem, and alpha interferon) provided level III evidence. All of the studies providing level I evidence used prospectively collected data and proper validation procedures with separate, randomly selected index and validation groups. However, most of the included studies did not provide an adequate description of the methods or the characteristics of included patients, which limited their generalizability.

CONCLUSIONS

Many limited-sampling strategies have been developed for anti-infective agents that do not have a clearly established link between AUC and clinical outcomes in humans. Future studies should first determine if there is an association between AUC monitoring and clinical outcomes. Thereafter, it may be worthwhile to prospectively develop and validate a limited-sampling strategy for the particular anti-infective agent in a similar population.

Good practice recommendations for outpatient parenteral antimicrobial therapy (OPAT) in adults in the UK: a consensus statement

These good practice recommendations for outpatient parenteral antimicrobial therapy (OPAT) are an update to a previous consensus statement on OPAT in the UK published in 1998. They are based on previous national and international guidelines, but have been further developed through an extensive consultation process, and are underpinned by evidence from published literature on OPAT. They provide pragmatic guidance on the development and delivery of OPAT services, looking at all aspects of service design, care delivery, outcome monitoring and quality assurance, with the aim of ensuring that OPAT services provide high-quality, low-risk care, whatever the healthcare setting. They will provide a useful resource for teams developing new services, as well as a practical set of quality indicators for existing services.

Challenges in assessing microbial susceptibility and predicting clinical response to newer-generation fluoroquinolones

PURPOSE

To determine the most appropriate methods for assessing the potential effectiveness of the newer topical fluoroquinolones gatifloxacin, moxifloxacin, and besifloxacin.

METHODS

This article is based on a literature search for published articles about the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of and measure of bacterial susceptibility to topical ophthalmic fluoroquinolones. Search terms included fluoroquinolones, susceptibility, resistance, minimal/minimum inhibitory concentration (MIC), PDs, PKs, and ocular, ophthalmic, or topical antibiotics.

RESULTS

Topical fluoroquinolones, particularly besifloxacin, gatifloxacin, and moxifloxacin, have become important treatment options for common ocular bacterial infections due to their broad-spectrum bactericidal activity and low toxicity. An important challenge in ophthalmology is identifying the most accurate in vivo and in vitro methods for evaluating the efficacy of these topical fluoroquinolones. The MIC is the most commonly used measure of in vitro susceptibility. In systemic therapy, this measure is combined with PK data of antibiotics to generate PD indices PK/PD whose breakpoints differentiate clinically susceptible from nonsusceptible bacterial pathogen populations. PD breakpoints are further tested in prospective studies for their ability to predict clinical efficacy. However, it is not known whether systemically derived breakpoints apply to the assessment of clinical susceptibility to ocular agents. Topical ocular antibiotics likely achieve higher concentrations at the target site than do systemically administered antibiotics, but these higher concentrations can be quickly reduced by reflex tearing and blinking induced by instillation. Hence, studies have been conducted in animals and humans to determine the PK concentrations of topically administered antibiotics in ocular compartments. When combined with MIC values for topical pathogens, the results have the potential to predict clinical efficacy after identification of the appropriate PK/PD target. Ocular studies incorporating PK/PD assessments have recently begun to be reported with newer fluoroquinolones, including besifloxacin, gatifloxacin, and moxifloxacin, whose prolonged contact time and potent bactericidal activity have translated into some of the most favorable PK/PD target values. However, the clinical relevance of these studies has yet to be determined.

CONCLUSION

There is still a clear need for predictive models to extend our understanding of the clinical susceptibility of ocular pathogens.

Impact of a Multidisciplinary Team Review of Potential Outpatient Parenteral Antimicrobial Therapy Prior to Discharge from an Academic Medical Center

Background::

Outpatient parenteral antimicrobial therapy (OPAT) is frequently prescribed at hospital discharge, often without infectious diseases (ID) clinician oversight. We developed a multidisciplinary team, including an ID pharmacist, to review OPAT care plans at hospital discharge to improve safety, clinical efficacy, practicality, and appropriateness of the proposed antimicrobial regimen.

Objective:

To evaluate the impact of the OPAT team on regimen safety, efficacy, and complexity; calculate the economic benefits of the service by avoiding hospital discharge delay, central venous catheter placement, or need for OPAT; and evaluate the discharge environment among OPAT referrals.

Methods:

In an observational design, we analyzed the impact of an OPAT team from July 2009 through June 2010 at a large academic tertiary care hospital. All patients with plans for continued parenteral therapy after discharge referred to the OPAT team were included in the analysis. Patients were excluded if OPAT was cancelled prior to processing of the referral.

Results:

During the 1-year study period. 569 of 644 consecutive referrals to the OPAT team met inclusion criteria, resulting in 494 OPAT courses. Interventions by an ID pharmacist were made for safety (56%), regimen complexity (41%), and efficacy (29%). Lack of formal ID physician consultation resulted in more interventions for safety (64% vs 48%, p < 0.001) and efficacy (36% vs 21%, p < 0.001). Discharge delays were avoided for 35 referrals, resulting in 228 hospital days avoided and approximately $366,000 in hospital bed cost savings. Use of OPAT was avoided in 75 referrals (13.2%), preventing central venous catheter placement in 48 patients (8.4%), resulting in an additional $58,080 in cost savings.

Conclusions:

The OPAT team optimized safety, efficacy, and convenience of OPAT while providing substantial cost savings. Further studies are needed to confirm the program's cost-effectiveness.

Clinical efficacy and cost-effectiveness of outpatient parenteral antibiotic therapy (OPAT): a UK perspective

OBJECTIVES

Outpatient parenteral antibiotic therapy (OPAT) is an effective treatment strategy for a wide variety of infections as long as clinical risk is minimized by conforming to practice guidelines. However, its cost-effectiveness has not been established in the setting of the UK National Health Service. We examined the clinical efficacy and cost-effectiveness of an OPAT service based in a large UK teaching hospital, predominantly using the outpatient 'infusion centre' and patient/carer administration models of service delivery.

PATIENTS AND METHODS

Data on clinical activity and outcomes were collected prospectively on 334 episodes of treatment administered by the Sheffield OPAT service between January 2006 and January 2008. Cost-effectiveness was calculated by comparing real costs of OPAT with estimated inpatient costs for these patient episodes incorporating two additional sensitivity analyses.

RESULTS

Of the OPAT episodes, 87% resulted in cure or improvement on completion of intravenous therapy. The readmission rate was 6.3%, and patient satisfaction was high. OPAT cost 41% of equivalent inpatient costs for an Infectious Diseases Unit, 47% of equivalent inpatient costs using national average costs and 61% of inpatient costs using minimum inpatient costs for each diagnosis.

CONCLUSIONS

Using this service model, OPAT is safe and clinically effective, with low rates of complications/readmissions and high levels of patient satisfaction. OPAT is cost-effective when compared with equivalent inpatient care in the UK healthcare setting.

Outpatient parenteral antibiotic therapy with daptomycin: insights from a patient registry

AIM

To compare and contrast the characteristics and clinical outcomes of patients who have received daptomycin as outpatients and inpatients.

METHODS

The Cubicin Outcomes Registry and Experience (CORE) is a retrospective chart review of patients who have received daptomycin in participating institutions. Patients treated in 2005 were included in this analysis. Demographic characteristics and clinical outcomes (success = cured + improved) were compared among patients who received outpatient parenteral antibiotic therapy (OPAT) and patients who had received inpatient parenteral antibiotic therapy (IPAT).

RESULTS

Of 1172 patients reported by 52 CORE 2005 participating institutions/investigators, 949 (81.0%) patients were evaluable: 539 (56.8%) received OPAT (OPAT patients), and 410 (43.2%) received only IPAT (IPAT patients). Of the 539 OPAT patients, 273 (50.6%) also received some IPAT, usually preceding OPAT therapy. Successful outcomes [no. of successes/(no. of successes + no. of failures)] for OPAT patients vs. IPAT patients were 94.6% and 86.3% respectively (chi-square test, p < 0.001). OPAT patients were younger, had fewer underlying diseases, were clinically stable, and had fewer adverse events than IPAT patients.

CONCLUSIONS

Outpatient parenteral antibiotic therapy use was common (539/949 or 56.8%) among patients in CORE 2005. Clinical outcomes among OPAT patients appeared at least as good as or better than IPAT patients. Better outcomes among OPAT patients were most likely because of patient selection for OPAT. Additional studies should focus on clinical characteristics of patients who would be ideal candidates for daptomycin OPAT.

Safety and efficacy of home intravenous antimicrobial infusion therapy in older patients: a comparative study with younger patients

BACKGROUND

Home intravenous antimicrobial infusion therapy has proved its safety and efficacy in a great number of infections. Despite this there are few published studies about this way of managing in the elderly patient.

OBJECTIVE

To study the safety and efficacy of home intravenous antimicrobial infusion therapy in elderly patients.

STUDY DESIGN

A prospective and comparative study of an elderly group of patients > or =70 years old vs. a cohort of younger adult patients as a control group. All patients were followed until 3 months after discharge.

SETTING

Hospital at Home Programme (HHP) as part of the Internal Medicine Department at Valle de Hebrón Hospital, Barcelona, Spain.

PATIENTS

All patients admitted to HHP diagnosed of infections requiring intravenous antibiotic therapy between March 2006 and March 2007.

RESULTS

We included 145 patients, 90 of whom were 70 years or older. Diabetes mellitus, heart failure and respiratory tract infection were more frequent in these elderly patients. In this group 14 (12%) developed some type of adverse event during treatment, phlebitis being the most common. The majority of those in the elderly patients group were discharged because of satisfactory clinical evolution and only 7 (7%) were re-admitted to hospital. Another 13 (14%) were re-admitted to hospital 3 months after discharge from HHP, mostly for chronic diseases. There were no significant differences between these results and those obtained from the control group.

CONCLUSION

Home intravenous antimicrobial infusion therapy in elderly patients is safe and effective.

Pharmacokinetics/pharmacodynamics of antibacterials in the Intensive Care Unit: setting appropriate dosing regimens

Patients admitted to Intensive Care Units (ICUs) are at very high risk of developing severe nosocomial infections. Consequently, antimicrobials are among the most important and commonly prescribed drugs in the management of these patients. Critically ill patients in ICUs include representatives of all age groups with a range of organ dysfunction related to severe acute illness that may complicate long-term illness. The range of organ dysfunction, together with drug interactions and other therapeutic interventions (e.g. haemodynamically active drugs and continuous renal replacement therapies), may strongly impact on antimicrobial pharmacokinetics in critically ill patients. In the last decade, it has become apparent that the intrinsic pharmacokinetic (PK) and pharmacodynamic (PD) properties are the major determinants of in vivo efficacy of antimicrobial agents. PK/PD parameters are essential in facilitating the translation of microbiological activity into clinical situations, ensuring a successful outcome. In this review, we analyse the typical patterns of antimicrobial activity and the corresponding PK/PD parameters, with a special focus on a PK/PD dosing approach of the antimicrobial agent classes commonly utilised in the ICU setting.

Effect of delayed pulsed-wave ultrasound on local pharmacokinetics and pharmacodynamics of vancomycin-loaded acrylic bone cement in vivo

This study sought to investigate the effect of delayed pulsed-wave ultrasound with low frequency on drug release from and the antimicrobial efficacy of vancomycin-loaded acrylic bone cement in vivo and the possible mechanism of this effect. After the implantation of cement and the inoculation of Staphylococcus aureus into the bilateral hips of rabbits, ultrasound (average intensity, 300 mW/cm(2); frequency, 46.5 kHz; on/off ratio, 20 min/10 min) was applied to animals in the normal ultrasound group (UG(0-12)) from 0 through 12 h after surgery and to those in the delayed-ultrasound group (UG(12-24)) from 12 through 24 h after surgery. The control group (CG) was not exposed to ultrasound. Based on vancomycin concentrations in left hip cavities at projected time intervals, the amount of time during which the local drug concentration exceeded the MIC (T(>MIC)) in UG(12-24) was significantly prolonged compared with that in either CG or UG(0-12), and the ratios between the areas under the concentration-time curves over 24 h and the MIC for UG(0-12) and UG(12-24) were both increased compared with that for CG. The greatest reductions in bacterial densities in both right hip aspirates and right femoral tissues at 48 h were achieved with UG(12-24). Local hemorrhage in rabbits of UG(0-12) during the 12-h insonation was more severe than that in rabbits of UG(12-24). Of four variables, the T(>MIC) and the bioacoustic effect were both identified as parameters predictive of the enhancement of the antimicrobial efficacy of cement by ultrasound. Sustained concentrations above the MIC replaced early high maximum concentrations and long-term subtherapeutic release of the drug, provided that ultrasound was not applied until local hemorrhage was relieved. The enhancement of the antimicrobial efficacy of cement by ultrasound may be attributed to the prolonged T(>MIC) and the bioacoustic effect caused by ultrasound.

Continuous wave ultrasound enhances vancomycin release and antimicrobial efficacy of antibiotic-loaded acrylic bone cementin vitroandin vivo

Although antibiotic-loaded bone cement (ALBC) is used as a drug delivery vehicle to decrease infection rates, the varied clinical effect of the antibiotic release remains controversial. The objective of this study is to investigate the enhancement of continuous wave ultrasound (CWU) on vancomycin release and antimicrobial efficacy of ALBC in vitro and in vivo. We measured vancomycin concentrations after a 0.5-h exposure of CWU. The results showed that CWU increased the drug elution by 2.57-27.44% when compared with the controls in vitro. Ultrasonic intensity and vancomycin load both had a significant effect on the cumulative drug elution at 10.5 h, with a significant interaction between each other. We also implanted ALBC specimens into hip joints of sixteen New Zealand White female rabbits after inoculations of Staphylococcus aureus around primary implants for 30 days. Vancomycin concentrations in the hip cavity and urinary elimination of vancomycin were both measured after intermittent exposures of CWU. The results showed that CWU increased local Tmax by 47.6 microg/mL and urinary elimination of vancomycin by 109.56 microg, but failed to prolong local T>MIC. On day 30 after the implantation, assessment in clinical performance, radiology, bacteriology, and histology all showed a tendency of decreased bacterial vitality and relieved inflammation in the infected hip treated by CWU. This study suggested that CWU could effectively enhance vancomycin release and antimicrobial efficacy of ALBC, which may be of clinical significance for treating prosthesis-related infections.

Principles of Antimicrobial Therapy

The most compelling reason for practicing judicious antimicrobial use is to facilitate therapeutic success. The definition of therapeutic success has changed in recent years, however; not only does success include eradication of infection, but it must now include avoidance of resistance. If the goal of antimicrobial therapy is to achieve sufficient concentrations at the site of infection such that the infecting organism is killed, therapy should be successful.

Functional Half-Life is a Meaningful??Descriptor of Steady-State??Pharmacokinetics of??an??Extended-Release Formulation of??a??Rapidly Cleared Drug

BACKGROUND

For many drugs, steady-state concentration-time profiles are often not optimally characterised by the intrinsic terminal elimination half-life for various reasons, including multiexponential disposition with minimal contribution of the terminal phase to steady-state exposure or use of controlled-release formulations with extended zero- or mixed zero-/first-order absorption. In such cases, 'effective' or 'functional' half-life (t((1/2)F)) has often been used to characterise steady-state pharmacokinetics. Valproic acid, commonly used in neuropsychiatry, has an elimination half-life of 4-16 hours in different populations (children vs adults, enzyme-induced vs uninduced). Divalproex-ER, a once-daily extended- release divalproex sodium formulation, is designed to release valproic acid over >18 hours. Hence the steady-state divalproex-ER concentration-time profiles have small peak-trough fluctuations that are not optimally characterised by valproic acid elimination half-life. In this study, the value of t((1/2)F) was calculated to characterise divalproex-ER steady-state concentration-time profiles.

METHODS

The value of t((1/2)F), defined as the time taken for the concentration to drop by one-half during a dosing interval (tau) at steady state, was derived using steady-state maximum (C(max)) and minimum (C(min)) plasma concentration and tau values, and calculated as ln(2)/(ln [C(max)/C(min)]/tau). The t((1/2)F) values of valproic acid in adult hepatic enzyme-uninduced healthy subjects and enzyme-induced epilepsy patients were calculated from five pharmacokinetic studies in which divalproex-ER was administered once daily for 6-14 days.

RESULTS

The estimated geometric mean t((1/2)F) in uninduced adults was 40.0 hours versus the expected elimination half-life of 12-16 hours in this population (including patients on valproic acid monotherapy); for induced patients, t((1/2)F) was 26.9 hours versus the expected elimination half-life of 6-12 hours.

CONCLUSION

The t((1/2)F) of valproic acid optimally characterises the expected steady-state C(max) to C(min )decrease of 33% in uninduced and 45% in induced adults following once-daily administration of divalproex-ER.

DRUG-DRUG INTERACTIONS OF ANTI-INFECTIVE DRUGS: UTILITY OF FLUORESCENCE CYP INHIBITION ASSAYS IN DRUG DISCOVERY

Drug interactions are often a result of induction or inhibition of cytochrome P450 (CYP) enzymes by co-administered drugs. A high throughput fluorescence assay using cDNA-expressed human CYP isozymes and fluorogenic substrates has been reported for the study of CYP inhibition. We used this assay to evaluate CYP inhibition profiles of 21 marketed anti-infective drugs. We found that six of the eight potent inhibitors identified in this screen (IC50 <10 microM against at least one CYP isozyme) correlated with significant drug-drug interactions in the clinic. In contrast, the intermediate and weak inhibitors (IC50 >10 microM) did not indicate clinically significant drug interactions. Furthermore, we observed that results obtained in the fluorescence assay correlated with conventional, well-established, low throughput methods that utilize human liver microsomes. These data suggest that in the early stages of drug discovery, the fluorescence assay for CYP inhibition could be used in conjunction with a human liver microsomal assay to identify new chemical entities with a potential for drug-drug interactions.

Meropenem Administered as a Prolonged Infusion to Treat Serious Gram-Negative Central Nervous System Infections

The treatment of gram-negative infection of the central nervous system (CNS) presents a clinical challenge due to antibiotic resistance and difficulties with penetration into the cerebrospinal fluid (CSF). Two patients with gram-negative CNS infections were treated successfully with high-dose, prolonged infusions of meropenem. The CSF meropenem concentrations exceeded the minimum inhibitory concentration of the pathogen for virtually the entire dosing interval in both cases. Our experience demonstrates that dosage modification to maximize pharmacodynamic targets and bactericidal activity may be practically applied to optimize antibiotic treatment for difficult-to-treat CNS infections.