Continuous infusion of beta-lactam antibiotics

Continuous beta-lactam infusion in critically ill patients: the clinical evidence

There is controversy over whether traditional intermittent bolus dosing or continuous infusion of beta-lactam antibiotics is preferable in critically ill patients. No significant difference between these two dosing strategies in terms of patient outcomes has been shown yet. This is despite compelling in vitro and in vivo pharmacokinetic/pharmacodynamic (PK/PD) data. A lack of significance in clinical outcome studies may be due to several methodological flaws potentially masking the benefits of continuous infusion observed in preclinical studies. In this review, we explore the methodological shortcomings of the published clinical studies and describe the criteria that should be considered for performing a definitive clinical trial. We found that most trials utilized inconsistent antibiotic doses and recruited only small numbers of heterogeneous patient groups. The results of these trials suggest that continuous infusion of beta-lactam antibiotics may have variable efficacy in different patient groups. Patients who may benefit from continuous infusion are critically ill patients with a high level of illness severity. Thus, future trials should test the potential clinical advantages of continuous infusion in this patient population. To further ascertain whether benefits of continuous infusion in critically ill patients do exist, a large-scale, prospective, multinational trial with a robust design is required.

In vivo efficacy and pharmacokinetics of biapenem in a murine model of ventilator-associated pneumonia with Pseudomonas aeruginosa

Biapenem (BIPM) has high bactericidal activity against Pseudomonas aeruginosa and similar activity in vitro as meropenem (MEPM). We used a murine model to examine the efficacy of biapenem against ventilator-associated pneumonia (VAP) caused by P. aeruginosa. Mice were treated by intraperitoneal injection with 100 mg/kg BIPM or MEPM every 12 h beginning 12 h after inoculation with P. aeruginosa. Survival was evaluated for 7 days, and 24 h after infection, lung histopathology was analyzed and the number of viable bacteria in the lungs and blood was counted. In addition, the pharmacokinetics of BIPM and MEPM were analyzed after the initial treatment. BIPM and MEPM significantly prolonged survival compared to control (P < 0.05). The lungs of mice treated with BIPM or MEPM had significantly fewer viable bacteria (3.54 ± 0.28 vs. 3.77 ± 0.14 log(10) CFU/ml) than in the lungs of control mice (6.65 ± 0.57 log(10) CFU/ml) (P < 0.05). Furthermore, viable bacteria were not detected in the blood of mice treated with BIPM or MEPM (control 2.85 ± 0.85 log(10) CFU/ml) (P < 0.05). Histopathological examination of lung specimens indicated that BIPM and MEPM prevent the progression of lung inflammation, including alveolar neutrophil infiltration and hemorrhage. The % time above MIC for BIPM and MEPM was 15.4% and 18.3% in plasma and 19.8% and 19.8% in lungs, respectively. These results show that BIPM and MEPM significantly prolongs survival and reduces the number of viable bacteria in a murine model of VAP caused by P. aeruginosa. Therefore, BIPM might be a potent and effective treatment for VAP caused by this bacterium.

Optimizing antimicrobial therapy in sepsis and septic shock

Every patient with sepsis and septic shock must be evaluated thoroughly at presentation before the initiation of antibiotic therapy. However, in most situations, an abridged initial assessment focusing on critical diagnostic and management planning elements is sufficient. Intravenous antibiotics should be administered as early as possible, and always within the first hour of recognizing severe sepsis and septic shock. Broad-spectrum antibiotics must be selected with one or more agents active against likely bacterial or fungal pathogens and with good penetration into the presumed source. Antimicrobial therapy should be reevaluated daily to optimize efficacy, prevent resistance, avoid toxicity, and minimize costs. Consider combination therapy in Pseudomonas infections, and combination empiric therapy in neutropenic patients. Combination therapy should be continued for no more than 3 to 5 days and de-escalation should occur following availability of susceptibilities. The duration of antibiotic therapy typically is limited to 7 to 10 days; longer duration is considered if response is slow, if there is inadequate surgical source control, or in the case of immunologic deficiencies. Antimicrobial therapy should be stopped if infection is not considered the etiologic factor for a shock state.

How I manage haematology patients with septic shock

Patients with a variety of haematological conditions are at risk of infection and its most serious complication: septic shock. Mortality for septic shock remains high and especially so in patients with haematological malignancy and following bone marrow transplantation. However, advances in the treatment of severe sepsis have improved mortality rates even though evidence for the management of severe sepsis in haematology patients is limited. Wherever possible this review will concentrate on evidence directly applicable to haematology patients but inevitably will have to extrapolate evidence from other patient groups. The Surviving Sepsis Guidelines 2008 provide information on best practice in the management of patients with severe sepsis and septic shock and are broadly applicable though not specific to haematology patients. This review summarizes a practical approach to the management of severe sepsis in haematology patients and highlights areas of research which may bring new treatments in the future. The review is limited to the management and initial resuscitation of septic shock in adult haematology patients and will not address the detailed intensive care management of these patients or the management of severe sepsis in children.

Nonlinear pharmacokinetics of piperacillin in healthy volunteers--implications for optimal dosage regimens

AIMS

(i) To describe the first-order and mixed-order elimination pathways of piperacillin, (ii) to determine the between occasion variability (BOV) of pharmacokinetic parameters and (iii) to propose optimized dosage regimens.

METHODS

We performed a five-period replicate dose study in four healthy volunteers. Each subject received 4g piperacillin as a single 5min intravenous infusion in each study period. Drug analysis was performed by HPLC. We used NONMEM and S-ADAPT for population pharmacokinetic analysis and Monte Carlo simulation to predict the probability of target attainment (PTA) with a target time of non-protein bound concentration above MIC >50% of the dosing interval.

RESULTS

A model with first-order nonrenal elimination and parallel first-order and mixed-order renal elimination had the best predictive performance. For a 70kg subject we estimated 4.40lh(-1) for nonrenal clearance, 5.70lh(-1) for first-order renal clearance, 170mgh(-1) for V(max) , and 49.7mgl(-1) for K(m) for the mixed-order renal elimination. The BOV was 39% for V(max) , 117% for K(m) , and 8.5% for total clearance. A 30min infusion of 4g every 6h achieved robust (≥90%) PTAs for MICs ≤12mgl(-1) . As an alternative mode of administration, a 5h infusion of 6g every 8h achieved robust PTAs for MICs ≤48mgl(-1) .

CONCLUSIONS

Part of the renal elimination of piperacillin is saturable at clinically used doses. The BOV of total clearance and volume of distribution were low. Prolonged infusions achieved better PTAs compared with shorter infusions at similar daily doses. This benefit was most pronounced for MICs between 12 and 48mgl(-1) .

Daily serum piperacillin monitoring is advisable in critically ill patients

The aim of the present study was to evaluate the benefit of monitoring serum piperacillin concentrations in critically ill patients. This was an 11-month, prospective, observational study in a 30-bed Intensive Care Unit in a teaching hospital, involving 24 critically ill patients with evidence of bacterial sepsis. All patients received a 66 mg/kg intravenous bolus of piperacillin in combination with tazobactam (ratio 1:0.125) followed by continuous infusion of 200mg/kg/24h. The dosage was adjusted when the serum piperacillin concentration either fell below 4x the drug's minimum inhibitory concentration (MIC) for the causative agent or exceeded the toxic threshold of 150 mg/L. With the initial regimen, serum piperacillin concentrations were within the therapeutic target range in only 50.0% of patients (n=12). This proportion increased to 75.0% (18 patients) (P=0.006) following dosage adjustment. For patients with low initial serum piperacillin concentrations (n=8), the percentage of time during which the concentration remained above 4x MIC (%T>4x MIC) was 7.1+/-5.9% before dosage adjustment and 27.3+/-8.6% afterwards. In conclusion, in critically ill patients, monitoring and adjustment of serum piperacillin levels is required to prevent overdosing and might also help to correct underdosing, an important cause of antibiotic therapy failure.

Optimizing antimicrobial therapy in sepsis and septic shock

This article reviews principles in the rational use of antibiotics in sepsis and septic shock and presents evidence-based recommendations for optimal antibiotic therapy. Every patient with sepsis and septic shock must be evaluated at presentation before the initiation of antibiotic therapy. However, in most situations, an abridged initial assessment focusing on critical diagnostic and management planning elements is sufficient. Intravenous antibiotics should be administered as early as possible, and always within the first hour of recognizing severe sepsis and septic shock. Broad-spectrum antibiotics must be selected with one or more agents active against likely bacterial or fungal pathogens and with good penetration into the presumed source. Antimicrobial therapy should be reevaluated daily to optimize efficacy, prevent resistance, avoid toxicity, and minimize costs. Consider combination therapy in Pseudomonas infections, and combination empiric therapy in neutropenic patients. Combination therapy should be continued for no more than 3 to 5 days and deescalation should occur following availability of susceptibilities. The duration of antibiotic therapy typically is limited to 7 to 10 days; longer duration is considered if response is slow, if there is inadequate surgical source control, or in the case of immunologic deficiencies. Antimicrobial therapy should be stopped if infection is not considered the etiologic factor for a shock state.

Continuous Infusion of Nafcillin for Sternal Osteomyelitis in an Infant After Cardiac Surgery

We report the use of the continuous infusion of nafcillin for the treatment of an infant who had methicillinsusceptible Staphylococcus aureus sternal osteomyelitis not responsive to traditional nafcillin dosing. The patient was successfully treated with surgical debridement and the continuous infusion of nafcillin. To our knowledge, this is the first report describing the successful use of the continuous infusion of nafcillin to treat an infant who had sternal osteomyelitis after cardiac surgery.

Continuous infusion of nafcillin for sternal osteomyelitis in an infant after cardiac surgery

We report the use of the continuous infusion of nafcillin for the treatment of an infant who had methicillinsusceptible Staphylococcus aureus sternal osteomyelitis not responsive to traditional nafcillin dosing. The patient was successfully treated with surgical debridement and the continuous infusion of nafcillin. To our knowledge, this is the first report describing the successful use of the continuous infusion of nafcillin to treat an infant who had sternal osteomyelitis after cardiac surgery.

Resurgence of Pseudomonas endocarditis in Detroit, 2006-2008

A resurgence of endocarditis due to Pseudomonas aeruginosa was seen in 10 injection drug users (IDUs) in Detroit between 2006 and 2008 (6 men, 4 women; mean age, 48.1 yr). All patients tested negative for the human immunodeficiency virus (HIV). Five patients had left-sided endocarditis of the mitral valve and/or the aortic valve; 3 of 5 patients had prosthetic valve endocarditis. Four of 10 patients had right-sided endocarditis of the tricuspid valve alone. One patient had bilateral involvement of the aortic and tricuspid valves. Nine patients had Pseudomonas endocarditis (PsE); 1 patient had mixed endocarditis with P. aeruginosa and Candida parapsilosis. Seven of 10 patients were treated with a combination of intravenous cefepime, 4-6 g/d, plus high-dose tobramycin (HDT) for at least 6 weeks. Tobramycin, 8 mg/kg per day, was given as a single daily dose intravenously, aiming for peak serum levels of 18-22 microg/mL and trough levels of <1 microg/mL. The patient with mixed endocarditis was also treated with fluconazole. Two patients initially treated with other antipseudomonal regimens, including cefepime alone and piperacillin/tazobactam plus tobramycin, failed treatment and were switched to cefepime and HDT. A third patient was switched to cefepime and ciprofloxacin because of nephrotoxicity. Two patients developed nephrotoxicity to tobramycin; 1 patient developed ototoxicity. The overall medical cure rate for both left-sided and right-sided disease was 80% (4/5). All 5 patients who required surgery survived (5/5; 100%). Overall outcome was 90% (9/10). Indications for valve replacement were recurrent Pseudomonas bacteremia (n = 3), recurrent bacteremia and congestive heart failure (n = 1), and persistent bacteremia and fungemia (n = 1). Tricuspid valvulectomy with valve replacement was successful in 2 patients and in a third patient who had successful replacement of both the tricuspid and the aortic valve for recurrent bacteremia and congestive heart failure. Two patients with pure left-sided prosthetic valve endocarditis underwent successful repeat valve replacements. Although this is a small series, the overall mortality rate (1/10; 10%) was low. The patient who did not survive had left-sided involvement of the aortic valve and could not undergo surgery because of a large embolic cerebral infarct. The mortality rate of left-sided disease in the current series was 16.7% (1/6 including the patient with tricuspid and aortic valve PsE) compared to 60% in a series of 15 patients reported in 1990.Our current antimicrobial regimen for PsE consists of a combination of cefepime, 6 g/d, in 3 divided doses, plus HDT, 8 mg/kg per day, given as a single daily dose for 6 weeks. For cefepime-resistant Pseudomonas, imipenem, 4-6 g/d, or meropenem, 6 g/d, plus HDT has been successful. For right-sided disease refractory to medical therapy, surgical intervention is recommended if Pseudomonas bacteremia persists for 2 weeks on appropriate antimicrobial therapy or if bacteremia recurs after a 6-week course of treatment. Tricuspid repair/reconstruction or valvulectomy with valve replacement plus combined antipseudomonal regimen may be the optimal therapy for refractory right-sided endocarditis. This approach not only may prevent the development of severe and permanent impairment of right ventricular function, which is a complication of valvulectomy alone without valve replacement, but also may cure the infection. For left-sided disease, surgery is recommended if blood cultures remain positive for 7 days on appropriate antimicrobial therapy or if Pseudomonas bacteremia recurs after completion of a 6-week course of the combined regimen.

Continuous-infusion oxacillin for the treatment of burn wound cellulitis

BACKGROUND

Burn cellulitis is an infection of the unburned skin at the margin of a burn wound or graft donor site, typically caused by group A beta-hemolytic streptococci and Staphylococcus aureus. beta-Lactam antibiotics exhibit time-dependent killing and, because of their narrow spectrum, minimize bacterial resistance. We therefore use continuous-infusion oxacillin in the treatment of burn cellulitis.

METHODS

Patients at a regional burn center who were treated for burn cellulitis from January 2003 to December 2005 were included. Charts were reviewed for all pertinent data regarding the antibiotic treatment methods and outcomes. Successful treatment was defined as resolution of physical findings, fever, and leukocytosis and intravenous antibiotic cessation.

RESULTS

Thirty-seven patients were treated for burn cellulitis, 26 (70%) of whom were treated initially with continuous-infusion oxacillin. Other initial antibiotics were chosen because of concomitant infections, penicillin allergy, or development of cellulitis during treatment with a beta-lactam antibiotic. Oxacillin treatment was successful in 19 patients (73%). Success required an average of 5.16 days, with 1.53 days required for fever resolution and 0.89 days for resolution of leukocytosis. Seven patients who did not respond rapidly were switched to intravenous vancomycin an average of 2.4 days after starting oxacillin, leading to a 100% success rate. There were no deaths, and only one suspected case of allergic reaction to oxacillin. In eleven patients treated with other antibiotics, the success rate was 75%. Success with these drugs required a longer treatment course of 6.45 days. Leukocytosis resolved significantly more slowly at 4.45 days (p = 0.02), and fever resolution was also slower at 3.18 days.

CONCLUSIONS

Continuous-infusion oxacillin was successful in the treatment of 73% of patients, a success rate that might have been higher with clinical patience, and leukocytosis resolved faster than with other antibiotics. Failure of continuous-infusion oxacillin can be managed without clinical consequence by conversion to intravenous vancomycin.

Comparison of the pharmacodynamics of biapenem in bronchial epithelial lining fluid in healthy volunteers given half-hour and three-hour intravenous infusions

The time above the MIC (T>MIC) is the pharmacokinetic/pharmacodynamic (PK/PD) parameter that correlates with the therapeutic efficacy of beta-lactam antibiotics. A prolonged infusion can provide plasma drug concentrations that remain above the MIC for a long period. The objective of this study was to compare the PK/PD parameters in bronchial epithelial lining fluid (ELF) of biapenem given as 0.5-h and 3-h infusions by using bronchoscopic microsampling (BMS). Six healthy adult volunteers received 0.5-h and 3-h infusions of 0.3 g of biapenem with a washout interval. BMS was performed repeatedly from 0.5 to 24 h after biapenem administration in order to determine the pharmacokinetics in bronchial ELF. The subjects received intravenous biapenem with the same regimens again and then underwent bronchoalveolar lavage (BAL) at the end of infusion in order to determine the concentration of the drug in alveolar ELF. The percentages (means +/- standard deviations) of T>MIC in bronchial ELF at MICs from 0.25 to 4 microg/ml ranged from zero to 34.6% +/- 5.2% after the 0.5-h infusion and from 5.1% +/- 5.6% to 52.2% +/- 17.0% after the 3-h infusion. The percentage of T>MIC in bronchial ELF after the 3-h infusion tended to be higher than that after the 0.5-h infusion. The concentrations of the drug in alveolar ELF after 0.5-h and 3-h infusions were 3.5 +/- 1.2 microg/ml and 1.3 +/- 0.3 microg/ml, respectively. The present results support the use of prolonged infusions of beta-lactam antibiotics and may provide critical information for successful treatment of lower respiratory tract infections based on PK/PD parameters in bronchial ELF.

Continuous versus intermittent infusion of oxacillin for treatment of infective endocarditis caused by methicillin-susceptible Staphylococcus aureus

Infective endocarditis (IE) is the fourth leading cause of life-threatening infection in the United States and imposes significant morbidity and mortality. The American Heart Association guidelines for the diagnosis and treatment of IE do not address continuous-infusion (CI) oxacillin. This retrospective study compares outcomes between CI oxacillin and intermittent-infusion (II) oxacillin in the treatment of IE caused by methicillin-susceptible Staphylococcus aureus (MSSA). A total of 709 medical records were reviewed for inpatients with definitive IE treated between 1 January 2000 and 31 December 2007. Continuous data were analyzed by Student's t test or the Wilcoxon rank sum test. The chi-square test or Fisher's exact test was used to compare nominal data. A multivariate logistic model was constructed. One hundred seven patients met eligibility criteria for inclusion into the study. Seventy-eight patients received CI oxacillin, whereas 28 received II oxacillin. CI and II groups were similar with respect to 30-day mortality (8% versus 10%, P = 0.7) and length of stay (20 versus 25 days, P = 0.4) but differed in 30-day microbiological cure (94% versus 79%, P = 0.03). Sixty-three patients received synergistic gentamicin, whereas 44 did not. The gentamicin and no-gentamicin groups were similar with respect to 30-day mortality (11% versus 4%, P = 0.2) and 30-day microbiological cure (90% versus 89%, P = 0.8); however, times to defervescence (4 versus 2 days, P = 0.02) were significantly different. CI oxacillin is an effective alternative to II oxacillin for the treatment of IE caused by MSSA and may improve microbiological cure. This convenient and pharmacodynamically optimized dosing regimen for oxacillin deserves consideration for patients with IE caused by MSSA.

Long-term stability of vancomycin hydrochloride in intravenous infusions

BACKGROUND AND OBJECTIVE

Vancomycin is often used in antibiotic infusions for hospitalized patients and it is advantageous to prepare such intravenous solutions in advance. The objective of this study was to investigate the long-term stability of this antibiotic stored at 4 degrees C in polyvinyl chloride (PVC) bags.

METHOD

Five bags each of 0.5 or 1 g vancomycin hydrochloride per 100 ml of 5% dextrose were studied for 2 months by high-performance liquid chromatography, visual inspection and pH measurement.

RESULTS

No colour change or precipitation was observed. The pH values of the preparations increased significantly over the period of study without influencing the antibiotic concentration. Based on a shelf-life of 90% residual potency, the vancomycin solutions were stable for at least 58 days at 4 degrees C.

CONCLUSION

From a chemical stability viewpoint, the antibiotic may be prepared in advance by a centralized intravenous admixture service for use within the limits described.

Continuous cefazolin infusion to treat bone and joint infections: clinical efficacy, feasibility, safety, and serum and bone concentrations

Cefazolin has been used for many years to treat bone and joint infections. Because of its time-dependent antimicrobial activity, continuous infusion would potentially be beneficial. We report on the feasibility, safety, and efficacy of prolonged continuous intravenous cefazolin therapy in a cohort of 100 patients, their serum cefazolin levels, and the concomitant bone cefazolin concentrations in 8 of them. This retrospective cohort study included all the patients treated for bone or joint infection with a continuous cefazolin infusion administered over a 12-h period twice daily for >or=2 weeks. Drug monitoring was performed at least twice for all the patients. Serum and bone cefazolin concentrations were determined by standardized disk diffusion microbiological assays. The absence of clinical, biological, and radiological signs of infection after 2 years of follow-up and the same criteria after 1 year of follow-up defined cures and probable cures, respectively. The median treatment duration was 42 days, and the median daily cefazolin dose was 6 g. Half of the patients received parenteral antibiotic therapy on an outpatient basis. Two moderate-grade adverse events were observed. The median serum cefazolin concentrations were 63 microg/ml (range, 13 to 203 microg/ml) and 57 microg/ml (range, 29 to 128 microg/ml) on days 2 to 10 and days 11 to 21, respectively. The median bone cefazolin concentration reached 13.5 microg/g (range, 3.5 to 29 microg/g). The median bone concentration/serum concentration ratio was 0.25 (range, 0.06 to 0.41). Among 88 patients with a median follow-up of 25 months (range, 12 to 53 months), 52 were considered cured and 29 were considered probably cured. Thus, the treatment of bone and joint infections with a prolonged continuous intravenous cefazolin infusion was feasible, effective, well-tolerated, safe, and convenient, making it a strong candidate for home therapy.

Alveolar concentrations of piperacillin/tazobactam administered in continuous infusion to patients with ventilator-associated pneumonia

OBJECTIVES

To determine the steady-state serum and alveolar concentrations of piperacillin/tazobactam administered in continuous infusion to critically ill patients with ventilator-associated pneumonia and various degrees of renal failure.

DESIGN

Prospective comparative study.

SETTING

An intensive care unit and research ward in a university hospital.

PATIENTS

Forty patients with microbiologically documented ventilator-associated pneumonia.

INTERVENTIONS

Patients were randomized to receive piperacillin/tazobactam daily continuous infusions of 12/1.5 g or 16/2 g after a loading dose of 4/0.5 g. The serum and alveolar piperacillin/tazobactam concentrations were determined at steady-state with high performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

The median (interquartile) serum and alveolar piperacillin concentrations were respectively 25.3 mg/L (23.1-32.6) and 12.7 mg/L (6.7-18.0) for 12/1.5 g/day, and 38.9 mg/L (32.9-59.6) and 19.1 mg/L (14.0-21.5), respectively, for 16/2 g/day in patients with no/mild renal failure. In patients with moderate/advance renal failure, the median (interquartile) serum and alveolar piperacillin concentrations were 102.4 mg/L (97.4-112.6) and 44.1 mg/L (33.4-48.3), respectively, for 12/1.5 g/day, and 135.3 mg/L (119.5-146.2) and 54.9 mg/L (45.2-110.3), respectively, for 16/2 g/day. Our results show great variability in piperacillin/tazobactam concentrations, with an alveolar percentage penetration of 40-50% for piperacillin and 65-85% for tazobactam and a negative association between serum or alveolar concentrations and creatinine clearance.

CONCLUSIONS

A target piperacillin serum concentration of at least 35-40 mg/L is probably required to provide alveolar concentrations exceeding the susceptibility breakpoint for gram-negative bacteria (16 mg/L) during ventilator-associated pneumonia. In patients with no/mild renal failure, a continuous daily dose of piperacillin/tazobactam 16/2 g allows reaching this target concentration, which might be not observed with 12/1.5 g/day. In patients with moderate/advanced renal failure, both dosages achieve serum concentrations far above the 35-40 mg/L threshold, suggesting that in that case, therapeutic drug monitoring should be performed in order to adjust the daily dose.

Pharmacokinetics of meropenem during intermittent and continuous intravenous application in patients treated by continuous renal replacement therapy

OBJECTIVE

The clinical effect of beta-lactam antibiotics depends on the time of drug concentration above the minimal inhibitory concentration (MIC) for a susceptible bacterium. Continuous infusion (CI) of beta-lactams such as meropenem may therefore be a more rational approach than intermittent bolus injections (IB). The aim of this study was to test whether CI of meropenem achieves effective drug concentrations comparable to IB in patients treated by continuous renal replacement therapy (CRRT).

DESIGN

Prospective, randomised cross-over study.

SETTING

Twelve-bed medical intensive care unit (ICU).

PATIENTS AND INTERVENTIONS

Six ICU patients were randomised to receive either meropenem 1 g IB every 12 h or a 0.5 g i.v. loading dose followed by 2 g i.v. CI over 24 h. After 2 days, regimens were crossed over. Meropenem pharmacokinetics were determined on days 2 and 4.

MEASUREMENTS AND RESULTS

Peak serum concentration [median (25% and 75% quartiles)] after short infusion of 1 g meropenem were 62.8 (51.4; 85.0) mg/l, trough levels at 12 h were 8.1 (4.5; 18.7) mg/l, and serum half-life was 5.3 (5.1; 7.0) h. Steady-state concentrations during CI were 18.6 (13.3; 24.5) mg/l. The AUCs during either treatment were comparable and determined as 233 (202; 254) mg/l*h (IB) and 227 (182; 283) mg/l*h (CI), respectively. Four hours after IB, drug concentrations dropped below CI steady-state concentrations.

CONCLUSION

Appropriate antibacterial concentrations of meropenem in patients with CRRT are easily achievable with CI. CI may be an effective alternative dosing regimen to IB. A prospective comparison of the clinical efficacy of the two dosage regimens is warranted.

Continuous versus intermittent infusion of temocillin, a directed spectrum penicillin for intensive care patients with nosocomial pneumonia: stability, compatibility, population pharmacokinetic studies and breakpoint selection

BACKGROUND AND AIMS

Temocillin, a 6alpha-methoxy-penicillin stable towards most beta-lactamases (including extended-spectrum beta-lactamase), is presented as an alternative to carbapenems for susceptible Enterobacteriaceae in microbiological surveys. We aimed at documenting its potential clinical usefulness in intensive care (IC) patients using pharmacokinetic/pharmacodynamic approaches applied to conventional (twice daily) and continuous infusion (CI) modes of administration.

METHODS

(i) In vitro evaluation of temocillin stability and compatibility with other drugs under conditions pertinent of CI in IC patients; (ii) pharmacokinetic study in patients treated by CI (4 g/day; n = 6) versus [twice daily (2 g every 12 h); n = 6]; (iii) population pharmacokinetic analysis of twice daily with Monte Carlo simulations to determine 95% probability of target attainment (PTA(95)) versus MIC (based on time above MIC > or = 40% for measured free drug).

RESULTS

Temocillin was stable at 37 degrees C in 8.34% solutions for 24 h and compatible with flucloxacillin and aminoglycosides, but not with several other antibiotic and non-antibiotic drugs. With CI, stable total serum concentrations were 73.5 +/- 3.0 mg/L (SEM) and free concentration 29.3 +/- 2.8 mg/L. With twice daily, Cmax (total drug) was 147 +/- 12.3 mg/L (SEM; free drug: 50.3 +/- 15.8 mg/L), lowest trough (total drug) 12.3 mg/L, and PTA(95) (free drug) obtained for MIC < or = 8 mg/L.

CONCLUSIONS

Temocillin (4 g/day) by CI yields stable free serum concentrations above the current breakpoint (16 mg/L), although individual variations may suggest lowering the breakpoint to 8 mg/L (as for twice daily) unless the daily dose or the frequency of administration is increased.

Continuous infusion of beta-lactams

PURPOSE OF REVIEW

Continuous infusion of beta-lactam antibiotics is becoming increasingly popular. The background and current clinical evidence are discussed. Tools to apply continuous infusion are analyzed.

RECENT FINDINGS

One randomized controlled trial in an ICU setting and two nonrandomized controlled trials have shown continuous infusion to be more beneficial than intermittent infusion. One randomized controlled trial in chronic obstructive pulmonary disorder patients, however, showed no difference between the two treatments. The stability of most beta-lactams for use during continuous infusion has been documented.

SUMMARY

Killing of bacteria by beta-lactam antibiotics is maximal at around four times the minimum inhibitory concentration in vitro. To ensure an optimal effect when treating severe infections, free unbound concentrations at or above four times the minimum inhibitory concentration should be maintained. Although continuous infusion has been demonstrated to be superior in animal studies, randomized clinical trials have failed to confirm this in humans, primarily because of suboptimal design. A better designed randomized clinical trial, set up as a pilot study, recently demonstrated a favorable outcome with continuous infusion. A major issue during continuous infusion is the stability of the antibiotic, which may limit its application. The calculation of the infusion rate necessary to obtain the desired free drug concentration is relatively straightforward.

Comparison of the Pharmacokinetics of Piperacillin and Sulbactam during Intermittent and Continuous Intravenous Infusion

BACKGROUND

The antibacterial effect of piperacillin/sulbactam depends on the time of drug concentration above the minimal inhibitory concentration (MIC). Therefore, continuous infusion (CI) may be a more rational approach than standard intermittent short-term infusion (SI). The study investigated whether CI achieves effective drug concentrations comparable with SI.

METHODS

Seven intensive care unit patients received either piperacillin/sulbactam as 4/1 g intravenous infusion over 15-20 min every 8 h or as 4/1 g intravenous loading dose (15-20 min) followed by 8/2 g intravenous CI per 24 h. After 2 days, regimes were crossed over.

RESULTS

Pharmacokinetic parameters (mean +/- SD) for SI piperacillin/sulbactam were: (1) peak serum concentration: piperacillin 231 +/- 66 mg/l, sulbactam 53.1 +/- 15.0 mg/l; (2) minimum serum concentration: piperacillin 11.5 +/- 14.8 mg/l, sulbactam 4.2 +/- 3.5 mg/l; (3) clearance: piperacillin 197 +/- 72 ml/min (CI 269 +/- 123 ml/min), sulbactam 167 +/- 61 ml/min (CI 212 +/- 109 ml/min); (4) half-life: piperacillin 2.4 +/- 1.2 h, sulbactam 3.1 +/- 1.6 h. Steady-state concentrations during CI were 25.5 +/- 14.5 mg/l for piperacillin and 8.0 +/- 3.7 mg/l for sulbactam. Average serum concentrations were comparable in both regimens.

CONCLUSION

A large German survey demonstrated that approximately 89% of Pseudomonas aerugionsa have an MIC < or =16 mg/l and approximately 82% have an MIC < or =8 mg/l. According to this threshold, appropriate anti-bacterial concentrations of piperacillin/sulbactam were achievable with CI. CI dosing has the additional advantage that less drug is necessary. Further prospective studies are warranted to compare the clinical efficacy of CI and SI regimens in bacterial infections.

Population pharmacokinetics and pharmacodynamics of continuous versus short-term infusion of imipenem-cilastatin in critically ill patients in a randomized, controlled trial

Beta-lactams are regularly administered in intermittent short-term infusions. The percentage of the dosing interval during which free drug concentrations exceed the MIC (fT(>MIC)) is the measure of drug exposure that best correlates with clinical outcome for beta-lactams. Therefore, administration by continuous infusion has gained increasing interest recently. We studied 20 critically ill patients with nosocomial pneumonia and investigated whether continuous infusion with a reduced total dose, compared to the standard regimen of intermittent short-term infusion, results in a superior probability of target attainment as assessed by the fT(>MIC) value of imipenem. In this prospective, randomized, controlled clinical study, patients received either a loading dose of 1 g/1 g imipenem and cilastatin (as a short-term infusion) at time zero, followed by 2 g/2 g imipenem-cilastatin per 24 h as a continuous infusion for 3 days (n = 10), or 1 g/1 g imipenem-cilastatin three times per day as a short-term infusion for 3 days (total daily dose, 3 g/3 g; n = 10). Imipenem concentrations in plasma were determined by using a validated liquid chromatography-tandem mass spectrometry assay. A two-compartment open model was employed for population pharmacokinetic modeling. We simulated 10,000 intensive-care-unit patients via Monte Carlo simulations for pharmacodynamic evaluation using the target 40% fT(>MIC). The probability of target attainment by MIC for intermittent infusion was robust (>90%) up to MICs of 1 to 2 mg/liter. The corresponding value for continuous infusion was 2 to 4 mg/liter. Although all 20 patients had an fT(>MIC) of 100%, 3 patients died. Patient survival was best described by employing a sepsis-related organ failure assessment score as a covariate in a logistic regression analysis. Larger clinical trials are warranted for evaluation of continuous infusions at a reduced dose of imipenem for critically ill patients.

Population pharmacokinetics at two dose levels and pharmacodynamic profiling of flucloxacillin

Flucloxacillin is often used for the treatment of serious infections due to sensitive staphylococci. The pharmacokinetic (PK)-pharmacodynamic (PD) breakpoint of flucloxacillin has not been determined by the use of population PK. Targets based on the duration of non-protein-bound concentrations above the MIC (fT(>MIC)) best correlate with clinical cure rates for beta-lactams. We compared the breakpoints for flucloxacillin between several dosage regimens. In a randomized, two-way crossover study, 10 healthy volunteers received 500 mg and 1,000 mg flucloxacillin as 5-min intravenous infusions. Drug concentrations were determined by high-pressure liquid chromatography. We used the programs WinNonlin for noncompartmental analysis and statistics and NONMEM for population PK and Monte Carlo simulation. We compared the probability of target attainment (PTA) for intermittent- and continuous-dosage regimens based on the targets of fT(>MIC)s of > or =50% and > or =30% of the dosing interval. The clearance and the volume of distribution were very similar after the administration of 500 mg and 1,000 mg flucloxacillin. We estimated renal and nonrenal clearances of 5.37 liters/h (coefficient of variation, 19%) and 2.73 liters/h (33%). For near maximal killing (target, fT(>MIC) of > or =50%) flucloxacillin showed a robust (> or =90%) PTA up to MICs of 0.75 to 1 mg/liter (PTA of 86% at 1 mg/liter) for a continuous or a prolonged infusion of 6 g/day. Short-term infusions of 6 g/day had a lower breakpoint of 0.25 to 0.375 mg/liter. The flucloxacillin PK was linear for doses of 500 mg and 1,000 mg. Prolonged and continuous infusion at a 66% lower daily dose achieved the same PK-PD breakpoints as short-term infusions. Prolonged infusion and continuous infusion are appealing options for the treatment of serious infections caused by sensitive staphylococci.

Treatment of Serratia marcescens meningitis with prolonged infusion of meropenem

OBJECTIVE

To describe the use of and cerebral spinal fluid (CSF) penetration of a prolonged infusion meropenem regimen in a patient with Serratia marcescens meningitis.

CASE SUMMARY

A 54-year-old female was diagnosed with S. marcescens meningitis associated with an epidural abscess 57 days after surgery for a herniated spinal disk. Meropenem 2000 mg every 8 hours was administered as a prolonged (3 h) infusion for the purpose of optimizing pharmacodynamic exposure. Meropenem concentrations were measured from the patient's blood and CSF (via a lumbar drain). The prolonged infusion regimen resulted in concentrations in both serum and CSF above the meropenem minimum inhibitory concentration (MIC) of 0.047 microg/mL for 100% of the dosing interval. After 6 days of therapy, the patient showed no further signs of infection and was subsequently discharged to a rehabilitation facility. At follow-up, she had completed a 4 week course of the prolonged infused therapy without relapse or adverse events.

DISCUSSION

Gram-negative infections of the central nervous system result in high morbidity and mortality. These infections are often difficult to treat because of poor antibiotic penetration coupled with increasing antibiotic resistance. Although there are 2 other case reports that describe the use of prolonged infusion of meropenem, our patient had a lumbar drain in place, thereby allowing us to collect multiple CSF samples and more accurately assess meropenem exposure at the site of infection. CSF penetration was 6.4% in this patient, resulting in 100% time above the MIC throughout the dosing interval.

CONCLUSIONS

In this patient with meropenem-susceptible S. marcescens meningitis, the use of a high-dose prolonged infusion of meropenem resulted in adequate exposure at the site of infection and a successful clinical response.

Continuous-infusion penicillin home-based therapy for serious infections due to penicillin-susceptible pathogens

To evaluate the feasibility of continuous-infusion (CI) penicillin in the treatment of serious bacterial infections, consecutive adult patients with deep-seated infections due to penicillin-susceptible pathogens were treated with CI aqueous penicillin G in a home-based programme, and their treatment outcomes were reviewed. Thirty-one patients with microbiologically proven infections completed the planned course of treatment. Twenty of 31 (65%) were followed for at least 2 months thereafter, and all remained free of relapse. One patient had fever attributable to penicillin hypersensitivity, two patients developed catheter-site infections and one patient developed catheter-related bacteraemia. Thus, CI penicillin is feasible for the home-based treatment of a variety of deep-seated infections with minimal toxicity.

Continuous administration of PBP-2- and PBP-3-specific β-lactams causes higher cytokine responses in murine Pseudomonas aeruginosa and Escherichia coli sepsis

OBJECTIVES

Initial antibiotic treatment of severe infections can lead to clinical deterioration due to sudden endotoxin release and concomitant exaggerated inflammatory response. Antibiotic-induced morphological changes may contribute to this phenomenon. High-dose ceftazidime, which inhibits penicillin-binding protein (PBP)-1 in Gram-negative bacteria, causes quick bacteriolysis and low endotoxin release. Low-dose ceftazidime leads to PBP-3 inhibition, which causes bacterial filament formation, associated with high endotoxin releases. PBP-2-specific antibiotics induce spheroplasts, again associated with low endotoxin release. We hypothesized that antibiotic type, concentration and regimen influence bacterial morphology, endotoxin levels and inflammatory response.

METHODS

Neutropenic mice with Escherichia coli or Pseudomonas aeruginosa sepsis were treated with ceftazidime or meropenem 10-320 mg/kg as an intravenous bolus or as continuous tail vein infusions of 0.1 mL/h. Four hours later, bacterial counts, morphology, plasma endotoxin, pro-inflammatory cytokines [tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6)] and antibiotic concentrations were measured.

RESULTS

Continuous infusion of 80 mg/kg ceftazidime was the lowest dose preventing filaments in E. coli infections. Bolus treatment resulted in filament formation, irrespective of the dose. During continuous treatment, IL-6 and TNF-alpha concentrations were higher compared with bolus treatment and controls for both antibiotics and both strains. A clear relationship between cfu counts in muscle and circulating IL-6 was shown (r=- 0.579, P=0.007), suggesting that plasma IL-6 is a valuable indicator of bacterial killing at the infection site.

CONCLUSIONS

Our findings show that not PBP affinity but the method of antibiotic administration is crucial during initial treatment of severe infections.

In vitro AN69 and Polysulphone Membrane Permeability to Ceftazidime and in vivo Pharmacokinetics during Continuous Renal Replacement Therapies

BACKGROUND

Ceftazidime is a third-generation cephalosporin almost entirely eliminated by glomerular filtration and dose reductions are essential in patients with renal impairment. The physicochemical and pharmacokinetic properties of ceftazidime make it susceptible to be eliminated by continuous renal replacement therapies (CRRT), but there is little clinical information to guide the correct administration in patients undergoing these techniques.

METHODS

In vitro procedures were carried out in three different fluids, using AN69 or polysulphone membranes. Four patients entered the in vivo study. Two patients received 1,000 mg every 6 h and the other two 2,000 mg every 6 h. Concentrations of ceftazidime were measured by high-performance liquid chromatography.

RESULTS

No differences were detected in thesieving coefficients (Sc) or saturation coefficients (Sa)between membranes during continuous venovenous hemofiltration (CVVH) or continuous venovenous hemodiafiltration (CVVHD). Sc-Sa values were close to 1 when Ringer's lactate was used as ceftazidime vehicle, but were lower in plasma samples (p < 0.05). In patients, the Sc-Sa was 0.93 +/- 0.06 and correlated well with the unbound fraction (0.86 +/- 0.08). The contribution of CRRT to ceftazidime clearance was higher in anuric patients than in nonanuric patients.

CONCLUSIONS

No differences were shown in vitro in the Sc obtained with both membranes during CVVH or the Sa obtained during CVVHD. The contribution of clearance by CRRT to total clearance is clearly dependent on the renal function. The administration of ceftazidime every 6 h could be associated with unnecessarily high trough levels which increase the risk of drug nephrotoxicity. Nonanuric patients undergoing CRRT need higher ceftazidime doses to reach adequate plasma concentrations against pathogens isolated in the critically ill.

Application of antimicrobial pharmacodynamic concepts into clinical practice: focus on beta-lactam antibiotics: insights from the Society of Infectious Diseases Pharmacists

In recent years there have been tremendous strides in understanding the relationship between the pharmacodynamics of beta-lactams and microbiologic response. For beta-lactams, in vitro and animal studies suggest that the amount of time in which free or non-protein-bound antimicrobial concentration exceeds the minimum inhibitory concentration (MIC) of the organism (fT>MIC) is the best predictor of bacterial killing and microbiologic response. Using population pharmacokinetic modeling and Monte Carlo simulation, it is possible to integrate pharmacokinetics, a pharmacodynamic target, and microbiologic surveillance data to generate empiric beta-lactam dosing strategies that maximize the likelihood of achieving fT>MIC associated with near maximal bactericidal effect against the range of pathogens encountered in clinical practice. At Albany Medical Center Hospital, these mathematical modeling techniques were used to devise alternative dosing schemes for piperacillin-tazobactam, meropenem, and cefepime. These alternative schemes optimized fT>MIC at a lower total daily dose than would be employed with traditional dosing methods. Moreover, they achieved the targeted fT>MIC with less administration time/day than would be needed for continuous infusion.

Continuous infusion of ceftazidime in critically ill patients undergoing continuous venovenous haemodiafiltration: pharmacokinetic evaluation and dose recommendation

Introduction

In seriously infected patients with acute renal failure and who require continuous renal replacement therapy, data on continuous infusion of ceftazidime are lacking. Here we analyzed the pharmacokinetics of ceftazidime administered by continuous infusion in critically ill patients during continuous venovenous haemodiafiltration (CVVHDF) in order to identify the optimal dosage in this setting.

Method

Seven critically ill patients were prospectively enrolled in the study. CVVHDF was performed using a 0.6 m² AN69 high-flux membrane and with blood, dialysate and ultrafiltration flow rates of 150 ml/min, 1 l/hour and 1.5 l/hour, respectively. Based on a predicted haemodiafiltration clearance of 32.5 ml/min, all patients received a 2 g loading dose of ceftazidime, followed by a 3 g/day continuous infusion for 72 hours. Serum samples were collected at 0, 3, 15 and 30 minutes and at 1, 2, 4, 6, 8, 12, 24, 36, 48 and 72 hours; dialysate/ultrafiltrate samples were taken at 2, 8, 12, 24, 36 and 48 hours. Ceftazidime concentrations in serum and dialysate/ultrafiltrate were measured using high-performance liquid chromatography.

Results

The mean (± standard deviation) elimination half-life, volume of distribution, area under the concentration-time curve from time 0 to 72 hours, and total clearance of ceftazidime were 4 ± 1 hours, 19 ± 6 l, 2514 ± 212 mg/h per l, and 62 ± 5 ml/min, respectively. The mean serum ceftazidime steady-state concentration was 33.5 mg/l (range 28.8–36.3 mg/l). CVVHDF effectively removed continuously infused ceftazidime, with a sieving coefficient and haemodiafiltration clearance of 0.81 ± 0.11 and 33.6 ± 4 mg/l, respectively.

Conclusion

We conclude that a dosing regimen of 3 g/day ceftazidime, by continuous infusion, following a 2 g loading dose, results in serum concentrations more than four times the minimum inhibitory concentration for all susceptible pathogens, and we recommend this regimen in critically ill patients undergoing CVVHDF.

Management of sepsis during the early "golden hours"

Severe sepsis and septic shock are common causes of morbidity and mortality. Interventions directed at specific endpoints, when initiated early in the "golden hours" of patient arrival at the hospital, seem to be promising. Early hemodynamic optimization, administration of appropriate antimicrobial therapy, and effective source control of infection are the cornerstones of successful management. In patients with vasopressor-dependent septic shock, provision of physiologic doses of replacement steroids may result in improved survival. Administration of drotrecogin alfa (activated), (activated protein C) has been shown to improve survival in patients with severe sepsis and septic shock who have a high risk of mortality. In this article we review the multi-modality approach to early diagnosis and intervention in the therapy of patients with severe sepsis and septic shock.

Influence of renal function on trough serum concentrations of piperacillin in intensive care unit patients

OBJECTIVE

To explore the effects of renal function estimated by measured creatinine clearance (Cl(CR)) on trough serum concentration (C(min)) of piperacillin given to critically ill patients.

DESIGN

Prospective observational study.

SETTING

An intensive care unit and research ward in a university hospital.

PATIENTS

Seventy critically ill patients, including 22 with severe trauma.

INTERVENTIONS

All subjects received an intravenous infusion of piperacillin 4 g three times (n = 61) or four times (n = 9) per day. Piperacillin C(min) values were determined 24 h after treatment started and compared to the French breakpoint defining antibiotic susceptibility against Enterobacteriaceae (8 mg/l) or Pseudomonas sp. (16 mg/l).

RESULTS

Median (range) piperacillin C(min) was 11.9 (< 1-156.3) mg/l, with a great variability among patients. Although the median value was close to the breakpoints, sub-therapeutic plasma levels were frequently observed. Piperacillin C(min) was lower than the breakpoint for Enterobacteriaceae in 37% of patients, and lower than the breakpoint for P. aeruginosa in 67% of them. A strong relationship was observed between piperacillin C(min) and Cl(CR): the higher the Cl(CR,) the lower the piperacillin C(min )in serum. For patients with a Cl(CR) < 50 ml/min, enough piperacillin C(min) was achieved in most patients with 12 g piperacillin per day. For patients with higher Cl(CR) values, a piperacillin daily dose of 16 g or more may be warranted.

CONCLUSIONS

In critically ill patients, therapeutic monitoring must be part of the routine, and knowledge of Cl(CR) value may be useful for the choice of adequate initial piperacillin dosing.

Randomized, open-label, comparative study of piperacillin-tazobactam administered by continuous infusion versus intermittent infusion for treatment of hospitalized patients with complicated intra-abdominal infection

The purpose of this randomized, multicenter, open-label study was to compare the continuous infusion of piperacillin-tazobactam with the standard intermittent infusion in 262 hospitalized patients with complicated intra-abdominal infections. Within 1 day of surgical intervention, eligible patients were randomized (1:1) to piperacillin-tazobactam 12 g/1.5 g administered continuously over 24 h or 3 g/0.375 g administered over 30 min intermittently every 6 h for 4 to 14 days. The demographics of the patients in the groups were similar, with a median APACHE II score of 7 and a median length of hospitalization of 7 days. Among 167 clinically evaluable patients, 86.4% and 88.4% of the patients treated with the continuous infusion and the intermittent infusion, respectively, were clinically cured or improved at the test-of-cure visit (P = 0.817). Bacteriological success was observed in 83.9% and 87.9% of patients (P = 0.597) in the two groups, respectively, and no differences in bacteriological response by pathogen were noted. Defervesence and white blood cell count normalization occurred in the majority of patients within 3 days and were similar between patients receiving the continuous infusion and those receiving the intermittent infusion. Drug-related adverse events were generally mild and were reported in similar numbers of patients in each arm of the trial. The results of this study support continuous infusion as a safe and reasonable alternate mode of administration of piperacillin-tazobactam for the treatment of complicated intra-abdominal infection.

[Blood and respiratory diffusion of antibiotics. A critical analysis of predictive parameters for clinical effectiveness]

The implementation of a treatment for lower respiratory tract infections must integrate a pharmacokinetic/pharmacodynamic (PK-PD) approach of antibiotic dosing. The activity of beta-lactam antibiotics is best predicted by the duration of time during which serum concentrations exceed the MIC (T>MIC). T>MIC of 30-40% is sufficient to achieve clinical cure in immunocompetent patients. This threshold is achieved with amoxicillin for penicillin susceptible or resistant Sreptococcus pneumoniae and with amoxicillin-clavulanate and ceftriaxone for S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. For macrolides, the activity is best predicted by T>MIC and for azithromycin and telithromycin by area-under-the-curve/MIC (AUC/MIC). Sufficient PK-PD values are only achieved for macrolides against susceptible strains of S. pneumoniae and against M. catarrhalis; for telithromycin, an AUC/MIC>25, which is necessary for bacterial eradication, is achieved in>99% of patients for S. pneumoniae and M. catarrhalis and>90% of patients for H. influenzae. For fluoroquinolones, both peak/MIC and AUC/MIC are predictors of clinical and bacteriological efficacy. AUC/MIC required ratios vary according to pathogens and severity of diseases from 48 to 125. These thresholds are reached for respiratory pathogens; for S. pneumoniae, AUC/MIC90 ratios of levofloxacin and moxifloxacin are 96 and 192, respectively; the presence of a mutation in parC increases the risk for the acquisition of additional mutations and failure.

Clinical efficacy of continuous infusion of piperacillin compared with intermittent dosing in septic critically ill patients

Since the bactericidal effects of beta-lactam antibiotics are time dependent, the optimum strategy for their administration could be continuous infusion. In this prospective, randomised controlled trial to evaluate the clinical efficacy of continuous infusion therapy, we evaluated the outcomes for 40 septic critically ill patients who received piperacillin either continuously (2 g intravenously (i.v.) over 0.5 h as a loading dose followed by 8 g i.v. daily over 24 h (n=20)) or as an intermittent infusion (3 g i.v. every 6h over 0.5 h (n=20)). Results from our study demonstrated that the clinical efficacy of piperacillin as a continuous infusion is superior to intermittent administration in critically ill patients. Change in APACHE II scores from baseline at the end of the second, third and fourth days, respectively, were 4.1, 5.1 and 5.2 for continuous infusion and 2.0, 2.6 and 2.8 for intermittent infusion (P< or =0.04). Considering minimum inhibitory concentrations (MICs) of 16 microg/mL and 32 microg/mL, the percentage of time for which piperacillin plasma concentrations were higher than the MIC (%T>MIC) was calculated for each patient in the two groups. For MICs of 16 microg/mL and 32 microg/mL, %T>MIC in the continuous infusion group was 100% and 65% of the dosing interval, respectively; in the intermittent infusion group, %T>MIC was only 62% and 39% of the dosing interval. There was a significant relationship between clinical results and laboratory data. It was shown that the superiority of the clinical efficacy of continuous infusion could be related to piperacillin pharmacodynamics. Continuous infusion significantly reduced the severity of illness as demonstrated by APACHE II scores during therapy.

[Outpatient parenteral antimicrobial therapy (OPAT) in bone and joint infections]

The medical treatment of many bone and joint infections (including chronic osteomyelitis, prosthetic joint infection, and septic arthritis) requires prolonged intravenous antimicrobial therapy. For some patients, this treatment could be administered outside the hospital in a program that offers outpatient parenteral antimicrobial therapy (OPAT). In France, we have no registry of patients receiving OPAT. Initiation of this program requires specific criteria based on a patient evaluation and selection, and an interdisciplinary team of professionals committed to high-quality patient care. Various vascular access devices and infusion pump therapy are used to administer OPAT. The most common parenteral agents for OPAT are beta-lactams and glycopeptids (specifically vancomycin). Antimicrobial courses are stopped prematurely in 3 to 10% of the cases because of an adverse reaction or vascular access complications. Several published studies demonstrate the effectiveness of OPAT and higher patient satisfaction than hospital care. In addition, OPAT is clearly more cost-effective than intravenous therapy provided in the hospital setting. Some diagnoses, such as cellulites, community-acquired pneumonia, and endocarditis may be managed with OPAT.