Aminoglycosides: single or multiple daily dosing? A meta-analysis on efficacy and safety

Amikacin treatment in urinary tract infection patients: evaluating the risk of acute kidney injury - a retrospective cohort study

The rise in ESBL-producing and carbapenem-resistant Gram-negative bacterial infections is alarming. Aminoglycosides remain attractive for treating urinary tract infections (UTIs). However, aminoglycosides-associated acute kidney injury (AKI) raises concerns, especially in patients with underlying renal impairment. We conducted a retrospective cohort study to evaluate the risk of AKI in patients with UTI empirically treated with amikacin. Among 395 patients (median age 41.9 years [IQR 28.3-67.1], 342 [86.6%] female), 162 (41.0%) received amikacin and 233 (59.0%) were empirically treated with other antibiotics. AKI incidence was low (5.6%) and not associated with amikacin exposure (OR 0.56, 95% CI 0.22-1.43, p = 0.23), even in those with pre-existing renal impairment or AKI on admission. The clinical outcomes (including cure by the third day, AKI, maximal creatinine, length of stay, mortality, and readmission) did not differ between the groups. Once-daily amikacin may offer a safe UTI treatment option amid increasing multi-drug resistance.

Safety considerations with new antibacterial approaches for chronic bacterial prostatitis

Introduction: Chronic bacterial prostatitis (CBP) is a difficult-to-eradicate infection. Antibacterial therapy with currently licensed agents is hindered due to the increasing emergence of pathogen resistance worldwide and to frequent infection relapse. With limited treatment options, physicians are investigating new agents, which, however, may raise safety concerns.Areas covered: Antibacterial agents currently licensed for CBP were not considered. Available reports about the safety and efficacy of antibacterial agents that have been clinically tested or tentatively used to treat CBP in single cases were evaluated. This review also focused on agents targeting Gram-positive pathogens, whose prevalence as causative agents of CBP is increasing.Expert opinion: (i) Most antibacterial agents considered in this review have been administered off-label in the interest of patients, and their use requires particular caution. (ii) Reports describing the usage of many of the drugs reviewed here are still scant, and readers should be warned of the limited published evidence supporting therapy for CBP with these agents. (iii) As treatment must extend over several weeks, medium-term adverse events may occur and therapy should be individualized, taking into account the dosage and the potential toxicity of each specific antibiotic. Regarding dangerous drug-drug interactions, particular attention should be paid to the risk of ECG-QT-interval elongation.

Gentamicin Vestibulotoxicity: Further Insights From a Large Clinical Series

OBJECTIVE

To review insights gained from a 21-year experience with gentamicin-induced vestibulotoxicity including differences in vestibulotoxicity between single daily dosing (SDD) and multiple daily dosing (MDD) regimens.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary care center.

PATIENTS

Patients with gentamicin vestibulotoxicity referred to the Hertz Multidisciplinary Neurotology Clinic between January 1993 and September 2014.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Spectrum of vestibular dysfunction measured using videonystagmography, vestibular evoked myogenic potentials, video head impulse testing, and magnetic scleral search coil testing.

RESULTS

Of 53 patients with gentamicin-induced vestibulotoxicity, 24 received SDD and 29 received MDD treatment. The most common indications for treatment were sepsis, endocarditis, and osteomyelitis. Angular acceleration receptor function (semicircular canals) was more commonly affected than linear acceleration receptor function (otolithic organ of the saccule; 100% vs. 62%). A significant proportion of patients (53%) developed vestibulotoxicity in the absence of nephrotoxicity and 40% experienced vestibulotoxicity in a delayed fashion up to 10 days posttreatment cessation (mean 3.9 ± 0.7). Therapeutic monitoring did not necessarily prevent delayed vestibulotoxicity. Nephrotoxicity was less common for SDD compared with MDD (60% vs. 35%, p = 0.01). However, the SDD group experienced vestibulotoxicity at a lower cumulative dose (6.3 vs. 7.0 g, p = 0.04) and shorter duration of therapy (20.7 vs 29.4 d, p = 0.02).

CONCLUSIONS

Our study further highlights important insights regarding gentamicin-induced vestibulotoxicity. While SDD is associated with decreased risk for nephrotoxicity compared with MDD, it confers a higher risk for vestibulotoxicity.

Risk of Nephrotoxicity in Patients With Drug-Resistant Tuberculosis Treated With Kanamycin/Capreomycin With or Without Concomitant Use of Tenofovir-Containing Antiretroviral Therapy

BACKGROUND

The intersection of HIV and drug-resistant (DR) tuberculosis (TB) presents the challenge of managing convergent drug toxicities.

METHODS

We conducted a retrospective study of adult patients with DR-TB treated with a kanamycin/capreomycin-based (KM) regimen, with or without concomitant antiretroviral therapy (ART). We estimated the incidence of nephrotoxicity (defined as an increase in serum creatinine greater than 26.5 µmol, or an increase in serum creatinine to 1.5 times the baseline value, or a decline in glomerular filtration rate to less than 60 mL/min/1.73 m), and evaluated the association between reported drug use and nephrotoxicity using Kaplan-Meier plots.

RESULTS

A total of 215 patients with DR-TB were treated with a kanamycin/capreomycin-based regimen, with or without concomitant ART. The incidence rate of nephrotoxicity was 3.6 [95% confidence interval (CI): 1.4 to 7.3], 6.9 (95% CI: 5.2 to 9.0), and 12 (95% CI: 3.3 to 30.9) cases per 100 person-months of follow-up in the KM only group (n = 42), the KM + TDF (tenofovir disoproxil fumarate) group (n = 163), and the KM + Other ART group (n = 10), respectively. Using the KM only group as a reference, the hazard ratio was 2.06 (95% CI: 0.92 to 4.63) in the KM + TDF group, and 4.09 (95% CI: 1.17 to 14.25) in the KM + Other ART group. Advancing age was an independent predictor of nephrotoxicity (adjusted hazard ratio 1.29, 95% CI: 1.14 to 1.46).

CONCLUSIONS

Our findings provide evidence of a significant risk of nephrotoxicity during treatment with a kanamycin/capreomycin-based DR-TB regimen, with or without concurrent treatment with ART. This study lends further support to calls for the substitution of TDF during the intensive phase of DR-TB treatment and for close monitoring of renal function during DR-TB treatment, especially in settings where the use of kanamycin/capreomycin is unavoidable.

In Vitro and In Vivo Characterization of NOSO-502, a Novel Inhibitor of Bacterial Translation

Antibacterial activity screening of a collection of Xenorhabdus strains led to the discovery of the odilorhabdins, a new antibiotic class with broad-spectrum activity against Gram-positive and Gram-negative pathogens. Odilorhabdins inhibit bacterial translation by a new mechanism of action on ribosomes.

Antibacterial activity screening of a collection of Xenorhabdus strains led to the discovery of the odilorhabdins, a new antibiotic class with broad-spectrum activity against Gram-positive and Gram-negative pathogens. Odilorhabdins inhibit bacterial translation by a new mechanism of action on ribosomes. A lead optimization program identified NOSO-502 as a promising candidate. NOSO-502 has MIC values ranging from 0.5 to 4 μg/ml against standard Enterobacteriaceae strains and carbapenem-resistant Enterobacteriaceae (CRE) isolates that produce KPC, AmpC, or OXA enzymes and metallo-β-lactamases. In addition, this compound overcomes multiple chromosome-encoded or plasmid-mediated resistance mechanisms of acquired resistance to colistin. It is effective in mouse systemic infection models against Escherichia coli EN122 (extended-spectrum β-lactamase [ESBL]) or E. coli ATCC BAA-2469 (NDM-1), achieving a 50% effective dose (ED₅₀) of 3.5 mg/kg of body weight and 1-, 2-, and 3-log reductions in blood burden at 2.6, 3.8, and 5.9 mg/kg, respectively, in the first model and 100% survival in the second, starting with a dose as low as 4 mg/kg. In a urinary tract infection (UTI) model with E. coli UTI89, urine, bladder, and kidney burdens were reduced by 2.39, 1.96, and 1.36 log₁₀ CFU/ml, respectively, after injection of 24 mg/kg. There was no cytotoxicity against HepG2, HK-2, or human renal proximal tubular epithelial cells (HRPTEpiC), no inhibition of hERG-CHO or Nav 1.5-HEK current, and no increase of micronuclei at 512 μM. NOSO-502, a compound with a new mechanism of action, is active against Enterobacteriaceae, including all classes of CRE, has a low potential for resistance development, shows efficacy in several mouse models, and has a favorable in vitro safety profile.

Magnesium and Drugs Commonly Used in Chronic Kidney Disease

As with other electrolytes, magnesium homeostasis depends on the balance between gastrointestinal absorption and kidney excretion. Certain drugs used commonly in patients with CKD can decrease gastrointestinal ingestion and kidney reclamation, and potentially cause hypomagnesemia. Other magnesium-containing drugs such as laxatives and cathartics can induce hypermagnesemia, particularly in those with impaired glomerular filtration and magnesium excretion. In this review, we will discuss the potential magnesium complications associated with a range of commonly encountered drugs in the care of CKD patients, discuss the potential mechanisms, and provide basic clinical recommendations.

Management of drug-resistant tuberculosis in special sub-populations including those with HIV co-infection, pregnancy, diabetes, organ-specific dysfunction, and in the critically ill

Tuberculosis remains a major problem globally, and is the leading cause of death from an infectious agent. Drug-resistant tuberculosis threatens to marginalise the substantial gains that have recently been made in the fight against tuberculosis. Drug-resistant TB has significant associated morbidity and a high mortality, with only half of all multidrug-resistant TB patients achieving a successful treatment outcome. Patients with drug-resistant TB in resource-poor settings are now gaining access to newer and repurposed anti-tuberculosis drugs such as bedaquiline, delamanid and linezolid. However, with ever increasing rates of co-morbidity, there is little guidance on how to manage complex patients with drug-resistant TB. We address that knowledge gap, and outline principles underpinning the management of drug-resistant TB in special situations including HIV co-infection, pregnancy, renal disease, liver disease, diabetes, and in the critically ill.

Nebulized Versus IV Amikacin as Adjunctive Antibiotic for Hospital and Ventilator-Acquired Pneumonia Postcardiac Surgeries: A Randomized Controlled Trial

OBJECTIVE

Nebulized antibiotics offer high efficacy due to significant local concentrations and safety with minimal blood levels. This study evaluates the efficacy and nephrotoxicity of nebulized versus IV amikacin in postcardiothoracic surgical patients with nosocomial pneumonia caused by multidrug-resistant Gram- negative bacilli.

DESIGN

Prospective, randomized, controlled study on surgical patients divided into two groups.

SETTING

Postcardiac surgery ICU.

INTERVENTIONS

The first gtroup was administered IV amikacin 20 mg/kg once daily. The second group was prescribed amikacin nebulizer 400 mg twice daily. Both groups were co-administered IV piperacillin/tazobactam empirically.

PATIENTS

Recruited patients were diagnosed by either hospital-acquired pneumonia or ventilator-associated pneumonia where 56 (42.1%) patients were diagnosed with hospital-acquired pneumonia, 51 (38.34%) patients were diagnosed with early ventilator-associated pneumonia, and 26 (19.54%) patients with late ventilator-associated pneumonia.

MEASUREMENTS AND MAIN RESULTS

Clinical cure in both groups assessed on day 7 of treatment was the primary outcome. Efficacy was additionally evaluated through assessing the length of hospital stay, ICU stay, days on amikacin, days on mechanical ventilator, mechanical ventilator-free days, days to reach clinical cure, and mortality rate. Lower nephrotoxicity in the nebulized group was observed through significant preservation of kidney function (p < 0.001). Although both groups were comparable regarding length of hospital stay, nebulizer group showed shorter ICU stay (p = 0.010), lower number of days to reach complete clinical cure (p = 0.001), fewer days on mechanical ventilator (p = 0.035), and fewer days on amikacin treatment (p = 0.022).

CONCLUSION

Nebulized amikacin showed better clinical cure rates, less ICU stay, and fewer days to reach complete recovery compared to IV amikacin for surgical patients with nosocomial pneumonia. It is also a less nephrotoxic option associated with less deterioration in kidney function.

Effects of atorvastatin on biomarkers of acute kidney injury in amikacin recipients: A pilot, randomized, placebo-controlled, clinical trial

BACKGROUND

The most common clinical indication of aminoglycosides (AG) is the treatment of serious Gram-negative infections. The aim of this study was to evaluate plausible effects of atorvastatin on the biomarkers of acute kidney injury (AKI) in patients receiving amikacin.

MATERIALS AND METHODS

In this double-blinded randomized clinical trial, fifty patients (25 in each group) receiving amikacin (15 mg/kg/day) were randomly assigned to either atorvastatin (40 mg/day) or placebo (40 mg/day) groups for 7 days. Blood urea nitrogen (BUN), serum creatinine (SCr), and urinary neutrophil gelatinase-associated lipocalin (NGAL) levels were measured at days 0, 1, and 7 of amikacin treatment.

RESULTS

During the study period, 4 (8%) patients including two patients in each atorvastatin and placebo group experienced AKI. Urine NGAL/urine Cr did not change significantly between and within placebo and atorvastatin groups during the study period. Similarly, the mean changes in SCr, BUN, and urine NGAL/urine Cr values did not differ significantly between and within patients with and without AKI.

CONCLUSION

Our data suggested that the changing pattern of urine NGAL/urine Cr ratio did not differ significantly between the atorvastatin and placebo groups during the early phase of amikacin treatment.

Once-Daily Aminoglycosides: A Meta-Analysis of Nonneutropenic and Neutropenic Adults

Objective:

To compare the efficacy, nephrotoxicity, and ototoxicity of once-daily dosing of aminoglycosides versus conventional dosing.

Design:

Meta-analysis of 14 randomized trials identified through a MEDLINE search (January 1965-May 1996).

Patients:

Neutropenic and nonneutropenic adults.

Interventions:

Patients were randomly selected to receive an aminoglycoside once daily or in multiple daily doses.

Measurements and Main Outcomes:

The outcomes considered were clinical cure, bacteriologic cure, nephrotoxicity, auditory toxicity, and vestibular toxicity. The data were analyzed in the following subgroups: (1) all trials, (2) nonneutropenic patients, (3) neutropenic patients, and (4) patients with undefined neutrophil status. For all trials the pooled risk ratio was 1.268 (95% CI 0.828 to 1.939) for clinical cure, and was 1.390 (95% CI 1.350 to 1.392) for bacteriologic cure. Nephrotoxicity had a pooled risk ratio of 0.765 (95% CI 0.468 to 1.252), that for auditory toxicity was 1.117 (95% CI 0.151 to 5.636), and that for vestibular toxicity was 1.155 (95% CI 0.221 to 6.039). Analysis of the subgroups, including a separate analysis of neutropenic patients, demonstrated similar results.

Conclusions:

When all trials were considered, once-daily administration of aminoglycosides had similar efficacy and no increase in nephrotoxicity or ototoxicity compared with conventional aminoglycoside dosing.

Extended-Interval Dosing of Aminoglycoside Antibiotics in Critically Ill Patients

Although aminoglycosides remain an essential part of therapy of severe gram-negative infections in critically ill patients, the use of extended-interval aminoglycoside dosing (EIAD) in this population is highly controversial. The rationale for EIAD is based on major pharmacodynamic characteristics of the aminoglycosides, which include concentration-dependent bactericidal effects, postantibiotic effect, and adaptive resistance. Alterations in the pharmacokinetics of aminoglycosides in the critically ill have been well documented, including changes in both drug distribution and elimination. These pharmacokinetic alterations may prevent critically ill patients from realizing the potential benefits of EIAD by reducing serum concentrations achieved by recommended EIAD regimens and may perhaps place patients at risk of therapeutic failure. Although numerous studies of EIAD have been conducted, there is a lack of data specifically concerning the efficacy and safety of EIAD in the critically ill. The most appropriate methods for monitoring EIAD in this population are also not clearly established. There are thus many questions regarding the suitability of EIAD in the critically ill. This article briefly reviews the rationale for EIAD and data related to the pharmacokinetics, efficacy, safety, and clinical monitoring of EIAD in critically ill patients. Considerations and recommendations for use of EIAD in the critically ill are provided.

Aminoglycoside-associated acute kidney injury in elderly patients with and without shock

OBJECTIVES

Multiresistant Gram-negative pathogens pose major healthcare concerns with a limited therapeutic armamentarium. Aminoglycosides (AG) are under-utilized due to nephrotoxicity. We aimed to evaluate AG-associated acute kidney injury (AG-AKI) in elderly inpatients, with and without shock.

METHODS

We examined the incidence and predictors of AG-AKI by KDIGO criteria and extended renal dysfunction (ERD) in patients aged >60 years. ERD represented a composite of hospital mortality or absence of renal recovery over 6 months following AG-AKI.

RESULTS

Two hundred and seventy-eight patients (aged 74 ± 8 years) were studied; 43% and 19% received >7 and >10 days of AG therapy, respectively, and 70% gentamicin (versus amikacin). Thirteen per cent had shock and 17% developed AG-AKI. Comparing all patients with shock versus no shock, AG-AKI developed in 33% versus 14%, respectively (P = 0.005); correspondingly among 47 patients with AG-AKI, more with shock had stage 2/3 AKI (92% versus 43%) and dialysis (50% versus 9%) (P < 0.01), but more had other strong AKI confounders than AG therapy alone (83% versus 40%, P = 0.02). Multivariate analyses identified mechanical ventilation, frusemide administration and AG therapy >10 days as predictors of AG-AKI (P < 0.05), whereas shock, pneumonia and frusemide administration predicted more severe stage 2/3 AG-AKI (P < 0.05). Hospital mortality was 30% versus 7% with AG-AKI versus none (P < 0.001). Twenty-three of 211 (11%) patients with extended analysis had ERD, with 47% experiencing renal recovery following AG-AKI. Mechanical ventilation and contrast administration during index hospitalization predicted ERD (P < 0.05).

CONCLUSIONS

AG-AKI is common in the elderly, with a significant risk of ERD, but the cause and severity are greatly influenced by critical illness and shock, more so than AG therapy alone.

Interactions of amikacin with the RNA model of the ribosomal A-site: computational, spectroscopic and calorimetric studies

Amikacin is a 2-deoxystreptamine aminoglycoside antibiotic possessing a unique l-HABA (l-(-)-γ-amino-α-hydroxybutyric acid) group and applied in the treatment of hospital-acquired infections. Amikacin influences bacterial translation by binding to the decoding region of the small ribosomal subunit that overlaps with the binding site of aminoacylated-tRNA (A-site). Here, we have characterized thermodynamics of interactions of amikacin with a 27-mer RNA oligonucleotide mimicking the aminoglycoside binding site in the bacterial ribosome. We applied isothermal titration and differential scanning calorimetries, circular dichroism and thermal denaturation experiments, as well as computer simulations. Thermal denaturation studies have shown that amikacin affects only slightly the melting temperatures of the A-site mimicking RNA model suggesting a moderate stabilization of RNA by amikacin. Isothermal titration calorimetry gives the equilibrium dissociation constants for the binding reaction between amikacin and the A-site oligonucleotide in the micromolar range with a favorable enthalpic contribution. However, for amikacin we observe a positive entropic contribution to binding, contrary to other aminoglycosides, paromomycin and ribostamycin. Circular dichroism spectra suggest that the observed increase in entropy is not caused by structural changes of RNA because amikacin binding does not destabilize the helicity of the RNA model. To investigate the origins of this positive entropy change we performed all-atom molecular dynamics simulations in explicit solvent for the 27-mer RNA oligonucleotide mimicking one A-site and the crystal structure of an RNA duplex containing two A-sites. We observed that the diversity of the conformational states of the l-HABA group sampled in the simulations of the complex was larger than for the free amikacin in explicit water. Therefore, the larger flexibility of the l-HABA group in the bound form may contribute to an increase of entropy upon binding.

Rational use of aminoglycosides--review and recommendations by the Swedish Reference Group for Antibiotics (SRGA)

The Swedish Reference Group for Antibiotics (SRGA) has carried out a risk-benefit analysis of aminoglycoside treatment based on clinical efficacy, antibacterial spectrum, and synergistic effect with beta-lactam antibiotics, endotoxin release, toxicity, and side effects. In addition, SRGA has considered optimal dosage schedules and advice on serum concentration monitoring, with respect to variability in volume of drug distribution and renal clearance. SRGA recommends that aminoglycoside therapy should be considered in the following situations: (1) progressive severe sepsis and septic shock, in combination with broad-spectrum beta-lactam antibiotics, (2) sepsis without shock, in combination with broad-spectrum beta-lactam antibiotics if the infection is suspected to be caused by multi-resistant Gram-negative pathogens, (3) pyelonephritis, in combination with a beta-lactam or quinolone until culture and susceptibility results are obtained, or as monotherapy if a serious allergy to beta-lactam or quinolone antibiotics exists, (4) serious infections caused by multi-resistant Gram-negative bacteria when other alternatives are lacking, and (5) endocarditis caused by difficult-to-treat pathogens when monotherapy with beta-lactam antibiotics is not sufficient. Amikacin is generally more active against extended-spectrum beta-lactamase (ESBL)-producing and quinolone-resistant Escherichia coli than other aminoglycosides, making it a better option in cases of suspected infection caused by multidrug-resistant Enterobacteriaceae. Based on their resistance data, local drug committees should decide on the choice of first-line aminoglycoside. Unfortunately, aminoglycoside use is rarely followed up with audiometry, and in Sweden we currently have no systematic surveillance of adverse events after aminoglycoside treatment. We recommend routine assessment of adverse effects, including hearing loss and impairment of renal function, if possible at the start and after treatment with aminoglycosides, and that these data should be included in hospital patient safety surveillance and national quality registries.

Once versus twice daily gentamicin dosing for infective endocarditis: a randomized clinical trial

OBJECTIVES

The aim of this randomized study was to investigate the effects of once versus twice daily gentamicin dosing on renal function and measures of infectious disease in a population with infective endocarditis (IE).

METHODS

Seventy-one IE patients needing gentamicin treatment according to guidelines were randomized to either once (n = 37) or twice daily (n = 34) doses of gentamicin. Kidney function (glomerular filtration rate, GFR) was measured with an isotope method ((51)Cr-EDTA) at the beginning of treatment and at discharge. Treatment efficacy was assessed by C-reactive protein (CRP) time to half-life, mean CRP and leukocytes.

RESULTS

Baseline GFR was similar in the two groups. Both groups displayed a significant fall in GFR from admission to discharge. The mean decrease in GFR was as follows: with once daily gentamicin, 17.0% (95% confidence interval 7.5-26.5), and with twice daily gentamicin, 20.4% (95% confidence interval 12.0-28.8). However, there was no significant difference in the GFR decrease between the once and twice daily regimens (p = 0.573). No difference in infection parameters was demonstrated between the two dosing regimens.

CONCLUSIONS

A twice daily gentamicin dosing regimen is neither less nephrotoxic nor more efficient than a once daily regimen in the treatment of IE patients. When indicated, gentamicin may therefore also be administered as a single-dose regimen in the treatment of IE patients.

Aminoglycoside use in renal failure

Aminoglycosides are the mainstay in the treatment of serious gram negative infections including catheter-associated infections. They are not metabolized and are rapidly excreted as such by glomerular filtration resulting in a plasma t^½ of approximately two hours in those with normal renal function. The t^½, however, can extend to 30-60 hours in patients who are functionally anephric; therefore, dosage reduction or modification is necessary in renal failure patients. In patients on hemodialysis the clearance of aminoglycosides is significant and variable. The concept of conventional postdialysis dosing in patients on hemodialysis needs to be revised in favor of higher predialysis doses to maintain effective bactericidal activity. This article is a brief review of the use of aminoglycosides in renal failure patients.

THE RISKS OF CONCURRENT TREATMENT WITH TENOFOVIR AND AMINOGLYCOSIDES IN PATIENTS WITH HIV-ASSOCIATED TUBERCULOSIS

Case study

Ototoxicity caused by once- and twice-daily administration of amikacin in rabbits

OBJECTIVE

The cochleotoxic effects of aminoglycosides, such as amikacin, are well-established. The aim of the present study was to investigate the possible differences in cochleotoxic effects between once-daily administration (ODA) and twice-daily administration (TDA) of amikacin simulating pediatric dosing.

METHODS

Twenty-one rabbits were used. Seven animals received intramuscularly amikacin once daily (ODA-group) and seven received the drug twice daily (TDA-group), for a total time period of 2 weeks. All the animals were subjected to Distortion Product Otoacoustic Emissions (DPOAEs) every 3 days since beginning of the experiment. The rest 7 animals did not receive any medication and served as controls (Control group). Two measurements (7 and 14 days) were obtained following the cease of drug administration.

RESULTS

Reduced cochlear activity (as depicted in the respective reduced DPOAE-amplitudes) compared to the pre-treatment state was found in both ODA- and TDA-groups. Cochlear activity was reduced at a wider range of frequencies (from 593 to 4031Hz in TDA-group and from 593 to 1093Hz in ODA-group) and to a higher degree in group B than in group A. Cochlear activity was reduced earlier in ODA-group than in TDA-group. No differences to the pre-treatment state were observed in the control group.

CONCLUSIONS

The above findings suggest that less frequent administration in higher dose of amikacin is associated with minimal cochleotoxicity.

Acute Myelogenous Leukemia and Febrile Neutropenia

Aggressive chemotherapy has a deleterious effect on all components of the defense system of the human body. The resulting neutropenia as well as injury to the pulmonary and gastrointestinal mucosa allow pathogenic micro-organisms easy access to the body. The symptoms of an incipient infection are usually subtle and limited to unexplained fever due to the absence of granulocytes. This is the reason why prompt administration of antimicrobial agents while waiting for the results of the blood cultures, the so-called empirical approach, became an undisputed standard of care. Gram-negative pathogens remain the principal concern because their virulence accounts for serious morbidity and a high early mortality rate. Three basic intravenous antibiotic regimens have evolved: initial therapy with a single antipseudomonal β-lactam, the so-called monotherapy; a combination of two drugs: a β-lactam with an aminoglycoside, a second β-lactam or a quinolone; and, thirdly, a glycopeptide in addition to β-lactam monotherapy or combination. As there is no single consistently superior empirical regimen, one should consider the local antibiotic susceptibility of bacterial isolates in the selection of the initial antibiotic regimen. Not all febrile neutropenic patients carry the same risk as those with fever only generally respond rapidly, whereas those with a clinically or microbiologically documented infection show a much slower reaction and less favorable response rate.

Once an empirical antibiotic therapy has been started, the patient must be monitored continuously for nonresponse, emergence of secondary infections, adverse effects, and the development of drug-resistant organisms. The averageduration of fever in serious infections in eventually successfully treated neutropenic patients is 4–5 days. Adaptations of an antibiotic regimen in a patient who is clearly not responding is relatively straightforward when a micro-organism has been isolated; the results of the cultures, supplemented by susceptibility testing, will assist in selecting the proper antibiotics. The management of febrile patients with pulmonary infiltrates is complex. Bronchoscopy and a high resolution computer-assisted tomographic scan represent the cornerstones of all diagnostic procedures, supplemented by serological tests for relevant viral pathogens and for aspergillosis. Fungi have been found to be responsible for two thirds of all superinfections that may surface during broad-spectrum antibiotic treatment of neutropenic patients. Antibiotic treatment is usually continued for a minimum of 7 days or until culture results indicate that the causative organism has been eradicated and the patient is free of major signs and symptoms. If a persistently neutropenic patient has no complaints and displays no evidence of infection, early watchful cessation of antibiotic therapy or a change to the oral regimen should be considered.

An overview of drug-induced acute kidney injury

The complex nature of critical illness often necessitates the use of multiple therapeutic agents, many of which may individually or in combination have the potential to cause renal injury. The use of nephrotoxic drugs has been implicated as a causative factor in up to 25% of all cases of severe acute renal failure in critically ill patients. Acute tubular necrosis is the most common form of renal injury from nephrotoxin exposure, although other types of renal failure may be seen. Given that this is a preventable cause of a potentially devastating complication, a comprehensive strategy should be used to avoid nephrotoxicity in critically ill patients including: accurate estimation of pre-existing renal function using serum creatinine-based glomerular filtration rates, avoidance of nephrotoxins if possible, ongoing monitoring of renal function, and immediate discontinuation of suspected nephrotoxins in the event of renal dysfunction.

Audiologic monitoring of multi-drug resistant tuberculosis patients on aminoglycoside treatment with long term follow-up

BACKGROUND

Multi-drug resistant tuberculosis has emerged as a significant problem with the resurfacing of tuberculosis and thus the need to use the second line drugs with the resultant increased incidence of adverse effects. We discuss the effect of second line aminoglycoside anti-tubercular drugs on the hearing status of MDR-TB patients.

METHODS

Sixty four patients were put on second line aminoglycoside anti-TB drugs. These were divided into three groups: group I, 34 patients using amikacin, group II, 26 patients using kanamycin and group III, 4 patients using capreomycin.

RESULTS

Of these, 18.75% of the patients developed sensorineural hearing loss involving higher frequencies while 6.25% had involvement of speech frequencies also. All patients were seen again approximately one year after aminoglycoside discontinuation and all hearing losses were permanent with no threshold improvement.

CONCLUSION

Aminoglycosides used in MDR-TB patients may result in irreversible hearing loss involving higher frequencies and can become a hearing handicap as speech frequencies are also involved in some of the patients thus underlining the need for regular audiologic evaluation in patients of MDR-TB during the treatment.

Aminoglycoside extended interval dosing in neonates is safe and effective: a meta-analysis

OBJECTIVES

To review the evidence from controlled clinical trials of neonates given equal daily aminoglycoside doses as extended interval dosing (dosage interval typically 24 hours in term and 36-48 hours in immature neonates) compared with traditional dosing (dosage interval typically 8-12 hours in term and 12-24 hours in immature neonates).

DESIGN

Systematic review and meta-analysis of controlled trials found in electronic databases, trial registers, and references in reviews and selected trials.

SETTINGS

The selected trials were blinded and assessed for methodological quality. Each trial's own predefined criteria for treatment failure, nephrotoxicity, ototoxicity, and therapeutic serum drug concentrations were used.

SUBJECTS

Controlled trials of neonatal aminoglycoside treatment in which equal aminoglycoside daily doses were given at traditional and extended dosage intervals.

MAIN OUTCOME MEASURES

Serum drug concentrations outside the therapeutic range. Treatment failure and toxicity.

RESULTS

Sixteen trials involving 823 neonates met the inclusion criteria for the systematic review. Twelve trials involving 698 neonates were included in the meta-analysis of the pharmacokinetics. Compared with traditional dosing, extended interval dosing was associated with a significantly lower risk of both peak (summary risk ratio 0.50, 95% confidence interval 0.26 to 0.94) and trough (0.36, 0.25 to 0.56) serum drug concentrations outside the therapeutic range. Accurate information on treatment failure was obtained in nine trials involving 555 neonates. One trial reported treatment failure. In this trial two neonates in the traditional dosing group did not respond to treatment within 72 hours. Nephrotoxicity was investigated in 589 neonates in 12 trials and ototoxicity in 210 neonates in four trials, with no significant differences between the two dosing regimens.

CONCLUSIONS

Extended interval dosing of aminoglycosides in neonates is safe and effective, with a reduced risk of serum drug concentrations outside the therapeutic range.

Pharmacokinetics and renal toxicity of three once-a-day doses of amikacin in cows

Pharmacokinetic variables of amikacin in cows were determined after administration of amikacin sulphate either intravenously (IV) or intramuscularly (IM) at a dose of 25 mg/kg per day for three days. Amikacin concentrations at time zero and maximum serum concentrations were 240.8 microg/mL and 122.53 microg/mL, respectively. The elimination half-life remained unchanged during the three days of administration (T1/2beta = 1.33 +/- 0.029 h for the IV route and T1/2beta = 2.75 +/- 0.38 h for the IM route). Apparent volumes of distribution suggest limited distribution out of the central compartment (VdAUC = 0.154 +/- 0.005 L/kg; Vdc = 36.50 +/- 2.35 L; Vdss = 0.092 +/- 0.004 L/kg). Bioavailability after IM administration was 95%. Serum profiles of urea, creatinine, albumin, electrolytes and pH after 5-day treatment with amikacin at a dose of 25 mg/kg per day IM revealed no changes. Assessment of diffusion of amikacin to milk by a commercially available screening method to detect antibiotic residues revealed that amikacin could not be detected by the fifth milking period after the last treatment. These results suggest that it would be rational to use a large single-daily dose of amikacin for future clinical trials in cows.

Current use for old antibacterial agents: polymyxins, rifampin, and aminoglycosides

This article discusses three classes of antibacterial agents that are uncommonly used in bacterial infections (other than mycobacterial infections) and can be thought of as special-use agents. These are the polymyxins, rifampin, and the aminoglycosides.

Application of Bayes theorem to aminoglycoside-associated nephrotoxicity: comparison of extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing

The objective of this study was to examine the incidence of aminoglycoside-associated nephrotoxicity related to extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing by applying Bayes theorem. An electronic literature search of MEDLINE (1966-2003) and a manual search of references from published meta-analyses and review articles were performed. Studies using extended-interval dosing, individualized pharmacokinetic monitoring, or multiple-daily dosing and reported aminoglycoside-associated nephrotoxicity for patients > or = 16 years of age were included. Quality scores were assigned based on the rigor of definition of aminoglycoside-associated nephrotoxicity, duration of therapy, and length of follow-up of renal function after completion of therapy. Inclusion criteria were then based on these quality scores. Quantitative data on the incidence of aminoglycoside-associated nephrotoxicity were abstracted. Twelve extended-interval dosing studies (n = 916), 10 individualized pharmacokinetic monitoring studies (n = 2066), and 27 multiple-daily dosing studies (n = 4251) met the inclusion criteria. Prior probabilities of aminoglycoside-associated nephrotoxicity were derived from a combination of a review of published studies and expert judgment. The maximum densities for the final posterior probabilities of aminoglycoside-associated nephrotoxicity for extended-interval dosing, individualized pharmacokinetic monitoring, and multiple-daily dosing were located at 12% to 13%, 10% to 11%, and 13% to 14%, respectively. Application of Bayes theorem demonstrates that aminoglycoside dosing by individualized pharmacokinetic monitoring results in less aminoglycoside-associated nephrotoxicity than extended-interval dosing or multiple-daily dosing.

Extended-interval aminoglycoside administration for children: a meta-analysis

BACKGROUND

There has been a long-standing debate regarding whether aminoglycosides should be administered on a multiple daily dosing (MDD) or once-daily dosing (ODD) schedule. Several unique characteristics of the aminoglycosides make ODD an attractive and possibly superior alternative to MDD. These include concentration-dependent bactericidal activity; postantibiotic effect, which allows continued efficacy even when serum concentrations fall below expected minimum inhibitory concentrations; decreased risk of adaptive resistance; and diminished accumulation in renal tubules and inner ear.

OBJECTIVE

To assess the relative efficacy and toxicity of ODD, compared with MDD, of aminoglycosides among pediatric patients.

STUDY SELECTION

Randomized, controlled trials among children, evaluating the relative efficacy and toxicity of ODD versus MDD of aminoglycosides, with similar total daily doses in the compared arms, were selected.

DATA SOURCES

PubMed (1966-2003) and Embase (1982-2003) databases, the Cochrane Controlled Trials Registry (2003), and references of eligible studies and pediatric review articles were searched.

DATA EXTRACTION

Study population characteristics and outcome data were extracted independently in duplicate, and consensus was reached on all items. The following outcome data were considered: (1) clinical or microbiologic failure, as defined in each study; (2) clinical failure; (3) microbiologic failure; (4) primary nephrotoxicity, ie, any rise in serum creatinine or decrease in creatinine clearance with thresholds as defined in each study; (5) secondary nephrotoxicity, ie, urinary excretion of proteins or phospholipids; and (6) ototoxicity based on pure tone audiometry, brainstem auditory evoked responses, or otoacoustic emissions for neonates and infants, vestibular testing, clinical impression, or any other method. All of the efficacy and toxicity outcomes were evaluated at the end of therapy.

RESULTS

Identification of eligible studies and study characteristics: 24 eligible studies published between 1991 and 2003 were identified. Aminoglycosides were used in different clinical settings (neonatal intensive care unit: 6 studies; cystic fibrosis: 3 studies; cancer: 5 studies; urinary tract infections: 4 studies; diverse infectious indications: 5 studies; pediatric intensive care unit: 1 study). Aminoglycosides used included amikacin (9 studies), gentamicin (11 studies), tobramycin (2 studies), netilmicin (2 studies), and tobramycin or netilmicin (1 study).

EFFICACY

There was no significant difference between ODD and MDD in the clinical failure rate, microbiologic failure rate, and combined clinical or microbiologic failure rates, but trends favored ODD consistently. There was no between-study heterogeneity for any outcome. Efficacy analysis of all trials indicating either clinical or microbiologic failures demonstrated pooled failure rates of 4.6% (23 of 501 cases) in the ODD arms and 6.9% (34 of 494 cases) in the MDD arms. The fixed-effects risk ratio was 0.71 (95% confidence interval [CI]: 0.45-1.11). A statistically significant benefit was seen with ODD over MDD in trials using amikacin, whereas no statistical significance was seen in trials using other antibiotics. The pooled clinical failure rates were 6.7% (22 of 330 cases) in the ODD arms and 10.4% (34 of 327 cases) in the MDD arms. The fixed-effects risk ratio was 0.67 (95% CI: 0.42-1.07). The pooled microbiologic failure rates were 1.8% (5 of 283 cases) with ODD and 4.0% (11 of 275 cases) with MDD. The fixed-effects risk ratio was 0.51 (95% CI: 0.22-1.18). NEPHROTOXICITY: There was no significant difference between ODD and MDD in the primary nephrotoxicity outcomes. Secondary nephrotoxicity outcomes were significantly better with ODD. The pooled primary nephrotoxicity rates were 1.6% (15 of 955 cases) in the ODD arms and 1.6% (15 of 923 cases) in the MDD arms. The fixed-effects risk ratio was 0.97 (95% CI: 0.55-1.69). The pooled secondary nephrotoxicity rates were 4.4% (3 of 69 cases) in the ODD arms and 15.9% (11 of 69 cases) in the MDD arms, suggesting a statistically significant superiority of ODD. The fixed-effects risk ratio was 0.33 (95% CI: 0.12-0.89). Results were consistent across types of clinical settings and aminoglycosides. OTOTOXICITY: There was no significant difference between ODD and MDD in the primary ototoxicity outcomes. The pooled ototoxicity rates for studies that provided auditory testing results were 2.3% (10 of 436 cases) in the ODD arms and 2.0% (8 of 406 cases) in the MDD arms. The fixed-effects risk ratio was 1.06 (95% CI: 0.51-2.19). In studies that provided clinical vestibular function testing results, no toxicity was documented among 209 patients given ODD and 206 patients given MDD. Studies noting only the clinical impression of hearing impairment also failed to identify any toxicity (ODD: 114 cases; MDD: 114 cases). SUBGROUP AND BIAS ANALYSES: We detected no statistically significant differences between ODD and MDD in any of the examined subgroups (neonatal intensive care unit, cystic fibrosis, cancer, or urinary tract infection), with respect to combined clinical or microbiologic failure outcomes, primary nephrotoxicity outcomes, or ototoxicity (based on auditory testing), when sufficient data were available. Moreover, there was no significant relationship between the effect size (risk ratio) and the trial size for any of the outcomes. DATA INTERPRETATION: Clinical failures were uncommon in the pediatric trials, regardless of the regimen used. If anything, fewer clinical failures tended to occur with ODD. Moreover, we observed a trend toward decreased bacteriologic failures. One meta-analysis of adult data suggested that ODD might reduce nephrotoxicity, whereas other meta-analyses showed nonsignificant trends or no difference in nephrotoxicity outcomes. In our meta-analysis, we were not able to show any reduction in the risk of primary nephrotoxicity outcomes with ODD. However, the event rate was much lower among children, compared with adults, and the secondary nephrotoxicity outcomes favored ODD. Finally, although the 2 regimens seemed equivalent with respect to ototoxicity, reporting on ototoxicity outcomes was incomplete. Reassuringly, even in the trials that performed auditory testing, the rates of ototoxicity in the MDD arms were very low. These results were consistent with meta-analyses of adult data, which showed no difference in ototoxicity rates between ODD and MDD.

CONCLUSIONS

Although single trials have been small, the available randomized evidence supports the general adoption of ODD of aminoglycosides in pediatric clinical practice. This approach minimizes cost, simplifies administration, and provides similar or even potentially improved efficacy and safety, compared with MDD of these drugs.

Extended-interval aminoglycoside dosing for treatment of enterococcal and staphylococcal osteomyelitis

BACKGROUND

Gram-positive osteomyelitis requires long-term antibiotic therapy, much of which is often administered in the outpatient setting. Historically, synergistic aminoglycoside use in these infections requires multiple daily doses, which can be inconvenient. Data regarding extended-interval aminoglycoside dosing (EIAD), also known as once-daily dosing, in this setting are lacking.

OBJECTIVE

To evaluate the safety and efficacy of EIAD in the treatment of gram-positive osteomyelitis.

METHODS

Retrospective chart review of adult patients treated for documented, gram-positive osteomyelitis with EIAD at the University of New Mexico Home IV Antibiotic Clinic was conducted. The patients' medical records were reviewed by an infectious diseases clinical pharmacist. Clinical and microbiologic outcomes and the incidence of nephrotoxicity and ototoxicity were the main outcome measures.

RESULTS

Fifteen patients (16 events) were included. Enterococcus spp. was the most common organism isolated. Nine patients had infected equipment or devices; 6 of these had removal of these devices in conjunction with antibiotic therapy. The median duration of antibiotic therapy was 6 weeks (range 6-31). The median duration of aminoglycoside therapy was 28 days (range 6-43). Seven patients developed nephrotoxicity, 5 of whom received an aminoglycoside in combination with vancomycin. Male patients had a higher risk of developing nephrotoxicity compared with females (p = 0.04). The mean +/- SD duration of EIAD before the development of nephrotoxicity was 34 +/- 8 days. Clinical cure was achieved in 12 (75%) patients. Three patients achieved clinical cure without hardware removal.

CONCLUSIONS

Most of the patients with gram-positive osteomyelitis were successfully managed with EIAD. However, nephrotoxicity developed in a high proportion of patients and was likely related to prolonged aminoglycoside use.

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

Some infectious diseases require management with parenteral therapy, although the patient may not need hospitalisation. Consequently, the administration of intravenous antimicrobials in a home or infusion clinic setting has now become commonplace. Outpatient parenteral antimicrobial therapy (OPAT) is considered safe, therapeutically effective and economical. A broad range of infections can be successfully managed with OPAT, although this form of treatment is unnecessary when oral therapy can be used. Many antimicrobials can be employed for OPAT and the choice of agent(s) and regimen should be based upon sound clinical and microbiological evidence. Assessments of cost and convenience should be made subsequent to these primary treatment outcome determinants. When designing an OPAT treatment regimen, the pharmacokinetic and pharmacodynamic characteristics of the individual agents should also be considered. Pharmacokinetics (PK) is the study of the time course of absorption, distribution, metabolism and elimination of drugs (what the body does to the drug). Clinical pharmacokinetic monitoring has been used to overcome the pharmacokinetic variability of antimicrobials and enable individualised dosing regimens that attain desirable antimicrobial serum concentrations. Pharmacodynamics (PD) is the study of the relationship between the serum concentration of a drug and the clinical response observed in a patient (what the drug does to the body). By combining pharmacokinetic properties (peak [C(max)] or trough [C(min)] serum concentrations, half-life, area under the curve) and pharmacodynamic properties (susceptibility results, minimum inhibitory concentrations [MIC] or minimum bactericidal concentrations [MBC], bactericidal or bacteriostatic killing, post-antibiotic effects), unique PK/PD parameters or indices (t > MIC, C(max)/MIC, AUC(24)/MIC) can be defined. Depending on the killing characteristics of a given class of antimicrobials (concentration-dependent or time-dependent), specific PK/PD parameters may predict in vitro bacterial eradication rates and correlate with in vivo microbiologic and clinical cures. An understanding of these principles will enable the clinician to vary dosing schemes and design individualised dosing regimens to achieve optimal PK/PD parameters and potentially improve patient outcomes. This paper will review basic principles of useful PK/PD parameters for various classes of antimicrobials as they may relate to OPAT. In summary, OPAT has become an important treatment option for the management of infectious diseases in the community setting. To optimise treatment course outcomes, pharmacokinetic and pharmacodynamic properties of the individual agents should be carefully considered when designing OPAT treatment regimens.

Pharmacodynamics and dosing of aminoglycosides

Aminoglycosides are concentration-dependent killing agents whose pharmacodynamic predictors of efficacy are the area-under-the-curve to minimum inhibitory concentration ratio and the peak to minimum inhibitory concentration ratio. Prospective studies have shown that these agents can be given once-daily or less frequently in most clinical settings, with equal efficacy and possible reduced toxicity. Dosages for different clinical settings have been studied and methods are available to monitor once-daily dosing.

Aminoglycoside-associated nephrotoxicity in the elderly

OBJECTIVE

To determine whether there was an increased incidence of nephrotoxicity in elderly patients (> or =65 y) prescribed single-dose (SD) versus multiple-dose (MD) aminoglycosides and whether aminoglycoside-induced nephrotoxicity was associated with length of therapy and other risk factors.

METHODS

A prospective, observational audit at a university teaching hospital was conducted. Physician prescribing was used to stratify subjects according to dosing regimen: MD (n = 60) or SD (n = 26). Nephrotoxicity was defined as an increase in the serum creatinine level of 0.5 mg/dL sustained over 2 days.

RESULTS

Eighty-six patients were included; 9.3% developed nephrotoxicity, of whom 62.5% received SD therapy. The incidence of nephrotoxicity did not differ between regimens (p = 0.051). There was an increased length of therapy in those who developed nephrotoxicity (mean +/- SD 6.1 +/- 6.2 vs. 3.7 +/- 2.8 d; p = 0.044). Additionally, patients who developed nephrotoxicity had an increased length of hospitalization (20.3 +/- 16.1 vs. 8.4 +/- 5.4 d; p < 0.001). Nephrotoxicity correlated with a diagnosis of diabetes mellitus (OR 15.1; 95% CI 1.11 to 205), concomitant angiotensin-converting enzyme (ACE) inhibitor therapy (OR 28.0; 95% CI 2.15 to 365), and SD therapy (OR 20.7; 95% CI 1.45 to 297).

CONCLUSIONS

Our overall incidence of nephrotoxicity is consistent with that reported in the literature. A diagnosis of diabetes mellitus, concomitant use of ACE inhibitors, and SD regimens were risk factors for the development of nephrotoxicity. An adequately powered, randomized trial is needed to assess whether a difference in the incidence of nephrotoxicity exists between SD and MD therapy in the elderly.

Extended interval aminoglycoside dosing: from concept to clinic

Extended-interval aminoglycoside dosing (EIAD), while a relatively recent concept in mainstream clinical practice, actually has its roots in the mid 1970s. Early trial and error approaches of manipulating the dosage regimen to avoid toxicity and improve efficacy have helped to characterize the pharmacodynamic properties of these drugs. The increasing successful use of EIAD and improved understanding of pharmacodynamics has helped this dosing regimen gain acceptance into routine clinical practice. A 1998 United States survey demonstrated that approximately 75% of hospitals have adopted EIAD into routine patient care. However, controversy still exists regarding some aspects of infrequent aminoglycoside administration, such as length of the drug-free interval and patient exclusion criteria. After more than 50 years of experience with the aminoglycosides we continue to learn how to most appropriately use these drugs.

Aminoglycoside nephrotoxicity: do time and frequency of administration matter?

Aminoglycosides remains the mainstay in the treatment of gram-negative infections despite their potential oto-and nephrotoxicity although alternatives with equal or better efficacy are available. Several approaches were investigated to decrease aminoglycosides nephrotoxicity. Among them, only the once-daily dosing of aminoglycosides has been brought to the clinic and physicians are now increasingly adopting this approach to reduce the toxicity of these agents. The incidence of aminoglycoside nephrotoxicity can be further reduced in view of the recent data on the circadian variations of their nephrotoxicity. In fact, it has been clearly demonstrated in both experimental animals and humans that the toxicity is maximal when the drug is injected during the rest period compared with the activity period. Thus, injecting aminoglycosides once-daily at the time of the lowest toxicity is actually the most interesting and clinically applicable approach to reduce aminoglycosides toxicity.

Pharmacodynamics of antiinfective therapy: taking what we know to the patient's bedside

Applied pharmacokinetics has long been a lifeline of clinical pharmacy services. National surveys during the past decade documented clinical pharmacy services and demonstrated that a substantial rate of growth occurred in clinical pharmacokinetic consultations and management of drug therapy protocols. Pharmacodynamic principles of antiinfective agents are rapidly becoming a new paradigm of clinical pharmacy services. beta-Lactams, aminoglycosides, and fluoroquinolones represent the three classes of antiinfective agents that have made the most progress toward the clinical applications of pharmacodynamics. Pharmacodynamic parameters are being used to select and compare agents within an antiinfective class (e.g., fluoroquinolones), make modifications in the dosage (e.g., extended-interval dosing of aminoglycosides) and/or mode of administration (e.g., continuous infusion of beta-lactams), develop in vivo breakpoint determinations, and assess the development of bacterial resistance. In addition, pharmacodynamic parameters have influenced the clinical drug development of new (e.g., linezolid) and older (amoxicillin-clavulanate, fluoroquinolones) antiinfective agents. Further investigations are needed to explore the clinician's use of validated prediction methods and patient-specific pharmacodynamic parameters at the bedside. By linking pharmacokinetic services with pharmacodynamic principles, the opportunity for continued progress toward our assessment and decisions for successful clinical outcomes is possible with old and new antiinfective agents.

Gentamicin dosing in critically ill patients

Gentamicin is used worldwide in the treatment of serious infections in critically ill patients. The therapeutic efficacy of gentamicin is correlated to the peak serum concentration and the adverse effects to the trough concentrations. Information concerning the pharmacodynamics in critically ill patients is scarce, but pharmacokinetic data are available. A once-daily dosage regimen has replaced multiple dosing of gentamicin in most intensive care units. No studies evaluating the superiority of either of these dosage recommendations in critically ill patients have ever been conducted. Based on 8 meta-analyses performed addressing this issue on a wide range of patients and theoretical considerations, we consider a once-daily dosage regimen feasible in critically ill patients. In septic patients the volume of distribution is significantly increased compared to normal patients, implying that the initial dose should be increased in this patient population. Additionally a general trend towards using higher loading doses (5-7 mg/kg) has been observed in USA, and the appropriateness of this dosing strategy is based on a large descriptive American study. We recommend that the initial dosage of gentamicin in critically ill hyperdynamic septic patients should be 7 mg/kg. Optimal and appropriate monitoring of the treatment with gentamicin in the critically ill patient is still an issue for further investigation. The treatment period with gentamicin should be short (3-5 days), bearing the pharmacological properties of aminoglycosides (small volume of distribution and poor tissue penetration) in mind. In patients with reduced renal function the initial dose of gentamicin should also be increased and maintenance dose reduced preferentially by prolonging the dosing intervals. However, the use of aminoglycosides in a high dose regimen in oliguric or anuric patients or patients who present with a rapidly decreasing renal function needs further consideration.

Antimicrobial pharmacodynamics

The ultimate goal of antimicrobial therapy is to provide the best possible outcomes for patients. For this to occur, the clinician should be cognizant of many clinical, microbiologic, pharmacologic, and epidemiologic data as well as fundamental pharmacodynamic concepts. An understanding of pharmacodynamic principles is essential; it forms the scientific basis for the design of dosing strategies that maximize clinical efficacy and minimize toxicity. In the 1990s, data accumulated from in vitro models of infection, animal models of infection, healthy volunteer studies, and clinical trials that have expanded knowledge on how drugs best kill microorganisms. This knowledge has enabled clinicians to establish the best modes of antibiotic administration to maximize the killing of microorganisms and to optimize clinical outcomes.

Cost Analysis of Pharmacy-Based Aminoglycoside Regimens: Once-Daily vs. Multiple Daily Dosing

A retrospective, case-controlled cost analysis was performed to compare the aminoglycoside-related costs of pharmacy-managed once-daily (ODA) and multiple-daily (MDA) gentamicin dosing in 274 patients. Outcome measures included the amount of drug and infusion-related supplies consumed, length of therapy, number of drug levels performed, and occurrence of nephrotoxicity. Costs were calculated based on outcome measures. Characteristics related to demographics, renal function, and site of infection were similar for both groups. The mean cumulative gentamicin dose per patient was greater in the ODA group (2223 mg) as compared with the MDA group (1169 mg), but median duration of therapy was similar in both groups (4 days). The ODA group required significantly fewer drug assays per patient than the MDA group (0.39 ± 0.63 and 1.1 ± 1.2, respectively; p < 0.01). Nephrotoxicity occurred in 1.4% of ODA patients and in 3% of MDA patients (p > 0.05). The mean costs per patient for the ODA and MDA groups were $85.66 and $140.61, respectively. Once-daily dosing of gentamicin was associated with a 65% reduction in therapeutic drug monitoring, a 53% reduction in rate of nephrotoxicity, and an overall reduction of 39% in total aminoglycoside-related costs (excluding cost of labor).]