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Urs Eriksson a Medicine B, University Hospital, University of
Zurich, CH-8091 Zurich, Switzerland, b Department of Biostatistics, University of Zurich
Correspondence
to: U Eriksson, Medicine A, University Hospital, CH-4031 Basel,
Switzerland on klinerr{at}usz.unizh.ch
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Abstract |
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Objective:
To test the hypothesis that amphotericin B deoxycholate is less toxic when given by continuous infusion than by
conventional rapid infusion.
Amphotericin B deoxycholate has remained the mainstay of treatment
for life threatening fungal infections in immunocompromised patients
because of its broad fungicidal activity and cheapness. Treatment with
amphotericin B, however, is associated with acute reactions related to
infusion and dose dependent nephrotoxicity. It is recommended that
amphotericin B is infused slowly over two to six hours, based on the
assumption that the severity and frequency of toxic reactions increase
during more rapid infusions.1-4
Incorporation of amphotericin B into liposomal formulations reduces its
toxicity, but the reasons for this are unclear.5-11 As
liposomes do not specifically target fungal cells it would seem that
the reduction in toxicity, at least in part, depends on a slower
delivery of amphotericin B to tissues. The question as to whether a
slower delivery of amphotericin B from lipid formulations might be
reproduced by a slow infusion rate therefore arises. The hypothesis
that a continuous infusion of amphotericin B results in reduced
toxicity has not been addressed yet in a prospective study. We
therefore conducted a randomised, controlled, and open trial to compare
the toxicity of amphotericin B given as a continuous infusion with a
conventional rapid regimen over four hours.
Inclusion and exclusion criteria and treatment
Design:
Randomised, controlled, non-blinded, single centre study.
Setting:
University hospital providing tertiary
clinical care.
Patients:
80 mostly neutropenic patients with
refractory fever and suspected or proved invasive fungal infections.
Intervention:
Patients were randomised to receive 0.97 mg/kg amphotericin B by continuous infusion over 24 hours or 0.95 mg/kg by rapid infusion over four hours.
Main outcome measures:
Patients were evaluated for
side effects related to infusion, nephrotoxicity, and mortality up to
three months after treatment. Analysis was on an intention to treat basis.
Results:
Patients in the continuous infusion group had
fewer side effects and significantly reduced nephrotoxicity than those
in the rapid infusion group. Overall mortality was higher during
treatment and after three months' follow up in the rapid infusion than
in the continuous infusion group.
Conclusion:
Continuous infusions of amphotericin B
reduce nephrotoxicity and side effects related to infusion without
increasing mortality.
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Introduction
Top
Abstract
Introduction
Patients and methods
Results
Discussion
References
![]()
Patients and methods
Top
Abstract
Introduction
Patients and methods
Results
Discussion
References
All consecutive patients at our tertiary referral centre for adult
internal medicine (Zurich University Hospital), including those at the
medical intensive care unit, were considered eligible for entry to the
study, providing their doctors had decided to start treatment with
amphotericin B. Exclusion criteria were a baseline serum creatinine
concentration in excess of 300 µmol/l or systemic treatment with
amphotericin B within the past seven days.
Outcome measures
Chills, rigors, and vomiting were monitored prospectively. Each
patient completed a standardised questionnaire daily until the end of
the study and was interviewed regularly. We also evaluated nursing
charts for any other adverse reaction. Temperature was measured at
least three times daily. Fever was defined as a core temperature of at
least 39.3°C (core temperature readings are 1°C above the
peripheral temperature readings). The concentrations of C reactive
protein were determined every 24 hours during the first three days and
at least every other day thereafter.
Statistics and study ethics
Analysis was on an intention to treat basis. The design of our
trial was based on a prior power calculation for the calculated serum
creatinine clearance at the end of treatment. The possible difference
between the study arms was estimated from a retrospective analysis of
patients receiving amphotericin B at our centre. We planned to
randomise 40 patients to each arm so as to achieve a power of 90% for
the detection of an effect size of [difference]/[standard
deviation]=0.8 when applying a two sided t test at the 5%
level. For the calculated creatinine clearance, this corresponds to a
difference of at least 20 ml/min between the treatments, assuming a
standard deviation of 25 ml/min within each group.
Our study was approved by the institutional
ethics committee of Zurich University Hospital. We obtained written consent from all patients at enrolment.
Assignment
The initial dosage for amphotericin B was chosen before
randomisation by the doctors in charge, who were not members of the
study team. Eligible patients were then randomised in blocks of 10 by
sealed envelope. Treatment started immediately after randomisation.
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Results |
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Patient flow and follow up
Figure 1 shows the flow of patients through the
trial. Patients were followed up three months after completion of
treatment or when treatment was discontinued for any
reason.
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Analysis
Patients
Overall, 86 consecutive patients received
amphotericin B during the study period. Most of them were severely
neutropenic, with haematological neoplasias. Of these patients,
only three had not been reported to the study team. One patient was not
eligible because of amphotericin B treatment within the past seven
days, and two did not give their consent. We enrolled 80 patients. The
study population also included patients with moderately impaired renal
function (baseline serum creatinine concentration less than 300 µmol/l). The groups did not differ significantly with regard to
treatment with aminoglycosides, vancomycin, diuretics, and granulocyte
colony stimulating factor. No patient received cyclosporin (table 1).
At enrolment the two groups did not differ significantly regarding
number of patients with refractory fever and probable and proved fungal
infections (table
2).
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Definitions
Refractory fever Persistent fever for more than 72 hours despite antibiotics in patients who are neutropenic (less than 500 neutrophils/µl) Possible fungal infections Persistent fever, neutropenia, chest symptoms, or the presence of pulmonary infiltrations on chest radiographs Probable fungal infections Persistent fever or increased concentration of C reactive protein, neutropenia, and infiltrates characteristic of fungal pneumonia on a computed tomogram Proved fungal infections Typical infiltrates on a computed tomogram and detection of moulds in bronchoalveolar lavage or bronchial secretions by culture and microscopy during neutropenia, or presence of pathogenic fungi in usually sterile sites |
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Overall duration of
treatment and cumulative and daily doses did not differ significantly
between the groups. There was a non-significant trend towards longer
duration of treatment and higher cumulative doses in the continuous
infusion group. We observed significantly more dose reductions or
infusion interruptions due to side effects in the rapid infusion group (table 3).
Side effects
The major side effects related to infusion
were chills, fever, and vomiting. They occurred mainly during the first
three days of treatment. We also observed flushing reactions, rashes,
and headaches. Patients receiving continuous infusions had fewer side
effects. We found significantly more patients with fever in the rapid
infusion group during the first 24 hours after treatment had started
(fig 2). For those who had fever at the beginning of treatment there
was also a significant difference in the mean time to defervescence
(table 3). The concentrations of C reactive protein did not differ
between the two groups at entry to the study, but there was a
significant increase in the rapid infusion group 24 and 48 hours after
the start of treatment. Concentrations gradually decreased from
baseline levels in the continuous infusion group (fig 3). Reflecting
the reduced frequency of side effects in the continuous infusion group,
these patients were less likely to receive drugs directed against
febrile reactions or chills after the first treatment day (table
3).
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The serum creatinine concentration or
calculated creatinine clearance did not differ between the two groups at baseline. Comparing the ratio of peak serum creatinine to baseline creatinine concentrations during and at the end of treatment, we found
a significantly higher ratio in the rapid infusion group (table 4). The
increase in serum creatinine concentration was reversible in all but
two patients, both assigned to the rapid infusion group, within three
months after treatment had been completed. Comparison of the calculated
creatinine clearance ratios between both infusion groups illustrates a
significantly less impaired creatinine clearance for patients with
continuous infusions during and at the end of treatment (table
4).
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Efficacy
All seven deaths during treatment occurred in the rapid infusion
group. Necropsy was carried out in six of these seven cases and severe
pneumonia was found. Invasive fungi were proved in three cases; in one
case Pneumocystis carinii was detected. In two patients no
infection was found. Breakthrough fungaemia did not occur in any
patient of either group (table 5).
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Discussion |
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Continuous infusions of amphotericin B are significantly better
tolerated than rapid infusions. Similar advantages of continuous infusions could be sought for other toxic drugs
for example,
antineoplastic agents. Continuous applications are, however, not
feasible if high peak values are necessary for efficacy (that is, with
aminoglycosides). The rapid infusion of amphotericin B over fewer hours
has been adopted empirically in clinical practice. Despite a
retrospective analysis suggesting fewer side effects from continuous
infusions, no controlled trials have compared rapid and continuous
infusions of amphotericin B .2
Our study was not blinded for practical reasons. Nevertheless, differences in toxicity between groups were evident regarding C reactive protein and creatinine concentrations, which were assessed at predetermined times and were not biased by the non-blinded study design. The reduction of side effects by continuous infusion of amphotericin B seems comparable to recent reports of liposomal amphotericin B (table 6),8 despite higher daily and cumulative doses being given in our study. Amphotericin B triggers a proinflammatory response by activating different cytokines. 20 21 Continuous infusions may be better tolerated because of delayed induction or release of such mediators, as reflected by differences in concentrations of C reactive protein and fever. We also observed a noticeable reduction of nephrotoxicity in the continuous infusion group. The mechanisms involved in amphotericin B nephrotoxicity are not yet fully understood.15 They can be broken down into pretubular and tubular effects. Pretubular effects, which include mainly a decrease in renal blood flow and glomerular filtration rate, are clearly reduced in patients having continuous infusions, as suggested by only a small decrease in calculated creatinine clearance. No noticeable difference was found in tubular effects between the two groups. Hypokalaemia was non-significantly decreased and tubular acidosis significantly decreased in the continuous infusion group. These observations are comparable to those in patients treated with liposomal amphotericin B: Walsh et al8 found no differences in the frequency of hypomagnesaemia between patients treated with liposomal amphotericin B and those receiving amphotericin B. In addition, they found only slight, although significant, differences in the frequency of hypokalaemia. Our study comprised only 80 patients. Nevertheless, hypokalaemia had been observed in 10 patients allocated to the rapid infusion arm compared with four patients in the continuous infusion group. Therefore, as with liposomal amphotericin B, a continuous infusion of amphotericin B primarily reduces pretubular toxicity.
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Indications for amphotericin B in our study were proved fungal infections, probable fungal infections, possible fungal infections, and refractory fever during neutropenia. Given the high mortality of invasive mycoses after a delay in treatment, amphotericin B is often prescribed empirically. A definitive baseline diagnosis of invasive mycosis would require invasive diagnostic procedures that are seldom justified in neutropenic and thrombocytopenic patients. It is therefore scarcely ever possible to identify the true prevalence of invasive mycoses, although clinical and radiological criteria (computed tomography) allow some risk stratification. For patients surviving proved mycoses during aplasia it is also difficult to assess efficacy of treatment. For instance, progressive changes in computed tomgrams of these patients may represent ongoing infection as well as host response after resolution of neutropenia.22 In addition, recovery from neutropenia in itself results in healing of invasive mycoses. As criteria for efficacy we therefore chose mortality, mortality due to invasive fungal infections, and breakthrough fungaemia. Although our study population was small for assessment of efficacy, the outcome was encouraging for continuous infusion. We found a higher overall mortality during amphotericin B in the rapid infusion group. Mortality also remained significantly higher after three months' follow up. Despite a higher number of proved or probable fungal infections in the continuous infusion group, three patients died with proved fungal infections at necropsy in the rapid infusion group whereas none died in the continuous infusion group. Accordingly, the death rate in the rapid infusion group was strongly influenced by the occurrence of invasive mycoses. Consequently, our data support the notion that a continuous infusion of amphotericin B may be at least as effective as daily infusions over four hours. We therefore recommend continuous infusions of amphotericin B , where practical, as an effective and well tolerated alternative to the usual rapid infusions.
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What is already known on this topic
Amphotericin B is the cornerstone for treatment of invasive fungal infections, especially in neutropenic patients Its use is limited by general toxic reactions and nephrotoxicity What this study addsBy giving amphotericin B as a continuous infusion, both nephrotoxicity and infusion related toxicity can be lowered significantly without loss of efficacy |
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Acknowledgments |
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We thank Dr K Barbatti for her help with data acquisition. Parts of this work were presented at the 39th interscience conference on antimicrobial agents and chemotherapy, 1999, San Francisco, California (organised by the American Society of Microbiology).
Contributors: UE was responsible for preparing, coordinating, performing, and analysing the clinical trial and is the principal author of the paper. BS was responsible for statistical design and analysis. AS had the original idea for the study and participated in designing the protocol and analysing the study data and is coauthor of the paper. UE and AS will act as guarantors for the paper.
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Footnotes |
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Funding: None.
Competing interests: UE has been reimbursed by Bristol-Myers Squibb, the manufacturer of amphotericin B deoxycholate (Fungizone), for attending the 39th interscience conference on antimicrobial agents and chemotherapy, 1999, San Francisco, California.
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References |
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(Accepted 4 December 2000)
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