Advances in novel antibiotics to treat multidrug-resistant gram-negative bacterial infections

Antimicrobial resistance is a growing threat to public health and an increasingly common problem for acute care physicians to confront. Several novel antibiotics have been approved in the past decade to combat these infections; however, physicians may be unfamiliar with how to appropriately utilize them. The purpose of this review is to evaluate novel antibiotics active against resistant gram-negative bacteria and highlight clinical information regarding their use in the acute care setting. This review focuses on novel antibiotics useful in the treatment of infections caused by resistant gram-negative organisms that may be seen in the acute care setting. These novel antibiotics include ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/cilistatin/relebactam, cefiderocol, plazomicin, eravacycline, and omadacycline. Acute care physicians should be familiar with these novel antibiotics so they can utilize them appropriately.

Once-Daily Plazomicin for Complicated Urinary Tract Infections

BACKGROUND

The increasing multidrug resistance among gram-negative uropathogens necessitates new treatments for serious infections. Plazomicin is an aminoglycoside with bactericidal activity against multidrug-resistant (including carbapenem-resistant) Enterobacteriaceae.

METHODS

We randomly assigned 609 patients with complicated urinary tract infections (UTIs), including acute pyelonephritis, in a 1:1 ratio to receive intravenous plazomicin (15 mg per kilogram of body weight once daily) or meropenem (1 g every 8 hours), with optional oral step-down therapy after at least 4 days of intravenous therapy, for a total of 7 to 10 days of therapy. The primary objective was to show the noninferiority of plazomicin to meropenem in the treatment of complicated UTIs, including acute pyelonephritis, with a noninferiority margin of 15 percentage points. The primary end points were composite cure (clinical cure and microbiologic eradication) at day 5 and at the test-of-cure visit (15 to 19 days after initiation of therapy) in the microbiologic modified intention-to-treat population.

RESULTS

Plazomicin was noninferior to meropenem with respect to the primary efficacy end points. At day 5, composite cure was observed in 88.0% of the patients (168 of 191 patients) in the plazomicin group and in 91.4% (180 of 197 patients) in the meropenem group (difference, -3.4 percentage points; 95% confidence interval [CI], -10.0 to 3.1). At the test-of-cure visit, composite cure was observed in 81.7% (156 of 191 patients) and 70.1% (138 of 197 patients), respectively (difference, 11.6 percentage points; 95% CI, 2.7 to 20.3). At the test-of-cure visit, a higher percentage of patients in the plazomicin group than in the meropenem group were found to have microbiologic eradication, including eradication of Enterobacteriaceae that were not susceptible to aminoglycosides (78.8% vs. 68.6%) and Enterobacteriaceae that produce extended-spectrum β-lactamases (82.4% vs. 75.0%). At late follow-up (24 to 32 days after initiation of therapy), fewer patients in the plazomicin group than in the meropenem group had microbiologic recurrence (3.7% vs. 8.1%) or clinical relapse (1.6% vs. 7.1%). Increases in serum creatinine levels of 0.5 mg or more per deciliter (≥40 μmol per liter) above baseline occurred in 7.0% of patients in the plazomicin group and in 4.0% in the meropenem group.

CONCLUSIONS

Once-daily plazomicin was noninferior to meropenem for the treatment of complicated UTIs and acute pyelonephritis caused by Enterobacteriaceae, including multidrug-resistant strains. (Funded by Achaogen and the Biomedical Advanced Research and Development Authority; EPIC ClinicalTrials.gov number, NCT02486627.).

Effectiveness of short-term antibiotic prophylaxis on postoperative recovery course after pulmonary lobectomies

BACKGROUND

Postoperative pneumonia is a major cause of mortality and morbidity after lung surgery. The effectiveness of prophylactic antibiotics for preventing postoperative pneumonia and the recovery course after pulmonary lobectomy is still not clarified yet. We conducted this study to evaluate the effectiveness of prophylactic antibiotics on the post-operative recovery course after pulmonary lobectomies.

METHODS

Forty-five cases undergoing pulmonary lobectomies between June 2002 and January 2003 were enrolled in this prospective study. Each patient received prophylactic antibiotics of cefuroxime and sisomicin. Sputum culture upon admission and swab culture from the bronchus cut-end during operation were obtained. The clinical vital signs including heart rates, respiratory rates and core body temperature in the postoperative recovery courses were analyzed.

RESULTS

Four (8.9%) patients developed pneumonia after lobectomies, and pneumonia occurred only in patients who had positive culture results from bronchial cut-end. The organisms cultured from the sputum seemed to be controlled by prophylactic antibiotics. All the organisms cultured in the bronchus cut-end differed from those in the sputum; it denoted these pathogens were inoculated during anesthesia for surgical operation. The postoperative vital signs including tachycardia and fever improved gradually in the initial 3 days. Patients with pneumonia sustained significant higher fever than the non-pneumonic patients during postoperative course.

CONCLUSIONS

The short-term combination of cefuroxime and sisomicin offers sufficient effectiveness in prophylaxis of pneumonia after pulmonary surgery. Positive bronchial cut-end cultures were related to the post-lobectomy pneumonia significantly. Body temperature was the most useful presenting vital sign for early detection of the postoperative pneumonia.

Distribution and serum concentration of sisomicin released from fibrin glue-sealed dacron graft in the rat and human

We investigated whether or not fibrin glue (FG) used as a sealant in vascular prostheses to prevent leakage might be useful as a carrier of antibiotics for the prevention of local graft infection. Sisomicin (SISO) was incorporated into fibrin glue (SISO-FG) and evaluated as to its safety and pharmacokinetics. SISO (1.75 mg) -FG Dacron grafts were implanted subcutaneously in the anterior abdominal region of Sprague-Dawley rats, and then the changes in SISO concentrations in the serum and in the tissue around the implantation sites were compared with those same sites in rats that had had intravenous injection of SISO (1.75 mg). The serum SISO concentrations were significantly lower in the SISO-FG Dacron graft group than they were in the intravenous injection group. However, until 4 h after implantation the SISO concentrations in the tissues around the implantation sites were significantly higher in the SISO-FG Dacron group than they were in the iv injection group, and the peak concentrations during that time were 5.8 times higher for the SISO-FG Dacron group than they were for the intravenous injection group. The ratio of the area under the tissue concentration time curve of SISO (AUC tissue) after implantation of the SISO-FG Dacron graft to that after intravenous injection of SISO was 13.08. Therefore, FG was considered to control the release of SISO into the serum and to maintain a high SISO concentration in the tissue around the implantation site. Clinically, SISO (45 mg) -FG was applied directly to the Dacron grafts implanted in 10 patients who underwent prosthetic vascular reconstruction. No graft infection was observed in any of the patients who received SISO-FG Dacron grafts. The mean serum concentration of SISO was 0.65+/-0.17 microg/mL after 1 h and 0.33+/- 0.21 microg/mL after 3 h. The results of these clinical applications are in close correlation with those of the animal experiment and suggest that FG is useful as a carrier of SISO, allowing its controlled release for the prevention of local infection.

Neuromuscular blocking actions of the aminoglycoside antibiotics sisomicin and micronomicin in the rabbit

The neuromuscular blocking actions of sisomicin sulfate (SISO), micronomicin sulfate (MCR) and d-tubocurarine (dTc) were studied in 20 rabbits anesthetized with halothane. The i.v. administration of SISO 20-40 mg/kg, MCR 40-80 mg/kg or dTc 0.1-0.3 mg/kg resulted in dose-dependent decreases in twitch tension. The ED50s for SISO, MCR and dTc were 23.5, 58.2 and 0.2 mg/kg, respectively. SISO- and MCR-induced neuromuscular blockade was partially antagonized by neostigmine or by calcium.

Prevention of vascular graft infection by sisomicin incorporated into fibrin glue

To examine the efficacy of sisomicin (SISO) incorporated into fibrin glue (FG) for the prevention of graft infection in animal models, the susceptibility to infection of Dacron grafts (control) and SISO-FG Dacron grafts following the inoculation of Staphylococcus aureus or S. epidermidis was compared. The results showed that SISO-FG Dacron grafts displayed resistance to graft infection.

[Morphologic rationale for selecting composition and structure of biologically active material based on sodium alginate for wound treatment]

Morphological evaluation of composition and structure of a biologically active compound (BAC) based on sodium alginate, comprising 1% sizomycin and 0.25% protease C, on wound healing in infected rats wounds was made in experiment. The results have clearly shown that for the infected wound treatment during the first period of wound healing BAC of polyfunctional action must be applied. Biologically active substances (sizomycin and protease C) promote removal of inflammatory etiopathogenic factors, i. e. necrotic tissues and microbic bodies, while polysaccharide basis of the composition promotes stimulation of reparative processes in the wounds. Powder with granules size 315 m including 24% potassium gluconate is believed most suitable BAC structure.

Failure of thiamphenicol in a penicillin-allergic patient with Listeria meningoencephalitis--delayed cure following penicillin desensitization

A 27-year-old woman, without compromised immunodefenses, experienced a Listeria meningoencephalitis, with brainstem symptoms. The identified agent exhibited poor susceptibility to usual effective antibiotics, except for penicillins. Knowledge of past history of an allergic reaction to beta-lactam antibiotics lead to appropriate therapy after acute intravenous desensitization of the patient to amoxicillin. Treatment resulted in therapeutic administration rate over 24 h, and in rapid regression of clinical and biological disorders.

[Antibiotics of the aminoglycoside group (gentamicin, sisomicin and amikacin) in the prevention and treatment of experimental plague]

Activity of aminoglycosides such as gentamicin, sisomicin and amikacin against plague microbe strains of natural origin was studied in vitro. It was also studied in prophylaxis and treatment of experimental plague infection in albino mice. The MAC of gentamicin and sisomicin for 50 strains of the plague microbe was 0.2-1.6 micrograms/ml. For the majority of the strains it was 0.4 micrograms/ml. The amikacin MICs were 0.4-3.2 and 0.8 micrograms/ml, respectively. High efficacy of gentamicin, sisomicin and amikacin was shown in prophylaxis and treatment of experimental plague infection in albino mice. The optimal doses of the antibiotics were determined. Under definite conditions such as the use of short-term regimens and higher intervals, advantages of sisomicin over gentamicin and amikacin in prophylaxis of experimental plague infection were observed.

[Pharmacokinetic monitoring of aminoglycoside therapy: an optimal method of administration of individualized doses of gentamicin and sisomicin]

One of the most promising approaches to design the optimal schedule for TDM provides a single determination of a drug content in the blood specimen being collected at the "ideal" sampling time equaled to the inverse value of the elimination rate constant. Three versions of the one-point method when the specimen was collected at the "ideal" time point (3 h after a single i.m. drug administration), as well as at the times of "maximum" (1 h after injection) and "minimum" (6 h after injection) concentrations were compared by the retrospective analysis of the routine TDM data obtained with HPLC-techniques in 47 patients treated with gentamicin or sisomicin. As optimal individualized doses were considered ones calculated on the base of three subsequent determinations of the aminoglycoside concentrations, i.e. 1, 3 and 6 h after injection, and the estimation of individual clearance values (Cli). The optimal doses (DCl) were calculated according to equation DCl = Dp.Cli/Clp, where Dp and Clp are population values of the dose (1 mg/kg) and Cl 72.4 ml/(h.kg), respectively. The approximate values of the individual doses (D) were calculated according to equation D = Dp.Cp/Ci, where Ci is the individual drug serum concentration 1, 3 or 6 h after administration and Cp is the corresponded population value (4.8, 1.9 and 0.8 mg/l, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Individual schedule of administration of aminoglycosides with reference to anatomo-physiological and pathological factors]

Potentiality of designing individual dosage of sisomicin and gentamicin in regard to "patient factors" was estimated. 62 adult patients with various pulmonary diseases at the background of volemic disorders of diverse degrees were treated with the aminoglycosides under monitoring of their blood levels. Concentrations of sisomicin and gentamicin in serum 1, 3 and 6 hours after their single administration in a dose of 1 mg/kg were determined by HELC. The antibiotic pharmacokinetics was characterized by pronounced individual variability. The ratio of the difference between the upper and lower confidence limits to the average values of the steady-state volume of distribution, the total clearance and the mean residence time amounted to 70, 60 and 57 per cent respectively. To elucidate the cause of the variability multiple correlation analysis of the pharmacokinetic parameters by the "patient factors" was performed. The highest coefficient of the multiple correlation (r = 0.690) defined relation between the aminoglycoside concentration 1 hour after the injection and the hematocrit, globular volume and phase of the volemic disorders which was expressed in coded variables. The coefficient of the multiple correlation between the total clearance and the body surface area, concentrations of creatinine and urea in serum, hematocrit, circulating blood volume and the phase of the volemic disorders was equal to 0.439. Therefore, the consideration of the above factors allowed to explain only 20 per cent of the observed individual variability of the pharmacokinetic parameters. In this connection mediated prediction of total clearance and subsequently individual dosage of the aminoglycosides by the "patient factors" was expedient only until the primary data on the pharmacokinetic monitoring were obtained.

[Pharmacokinetic monitoring of antibiotic therapy]

The general strategy in optimization of antibiotic dosage regimens included development of population or common regimens for an "average" patient (the 1st approximation), subpopulation regimens for patients of certain categories on the basis of interactions between the pharmacokinetic parameters and "patient factors" (the 2nd approximation) and individual regimens on the basis of the data of the pharmacokinetic monitoring (the 3rd approximation). Characteristics of every of the approximations in antibiotic therapy of adults and children were analyzed. Out of the peculiarities of the strategy use in pediatrics+ and micropediatrics+ the following should be indicated: (1) pharmacokinetic heterogeneity of the population requiring grouping of the patients and consequently development of subpopulation dosage regimens omitting stage I, (2) possible development of dosage regimens on the basis of the ration between the pharmacokinetic parameters or immediate drug concentration values and the "patient factors" not only in chronic but also in transitory impairment of some functions and (3) the necessity of considering systematic changes in "pharmacokinetic status" of every child during individualization of the dosage regimens by the data of the pharmacokinetic monitoring.

[Correlation of dose-antimicrobial effect in modeling in vitro pharmacokinetic profiles of normal and impaired elimination of antibiotics]

Relationships between concentration and antimicrobial effect (AME) of sisomicin (SMN) and cefotaxime (CTX) were established by simulating their pharmacokinetic profiles in an in vitro dynamic model. The AME duration (TE, time shift between the curves of bacteria heat output in the presence and absence of the antibiotics) or intensity (IE, area between the above curves) for both the antibiotics depended in the same way on the area under the concentration/time curve (AUC, mimicing of intravenous administration of the antibiotics in various doses). At low and moderate values of the AUC the dependences of IE or TE vs the AUC (the bacteriostatic phase of the AME development) were of the sigmoid shape while at high values of the AUC there was a marked increase in IE or TE (the bactericidal phase). The patterns of the IE or TE vs AUC curves in impaired antibiotic elimination were analogous. At the same time the IE or TE vs AUC curves for both the antibiotics under simulation of normal elimination (T 1/2, SMN-2.1 h, T 1/2, CTX-1.2 h) and impaired one (T 1/2, SMN-8.3 h, T 1/2, CTX-4.6 h) did not match. In the first case the AMESMN was on the whole higher and the AMECTX was lower than in the second case. Therefore, in patients with renal failure the efficient concentration of the aminoglycoside in blood can be higher and that of the cephalosporin on the contrary can be lower than the normal.

Pre-column derivatization of sisomicin with o-phthalaldehyde-beta-mercaptopropionic acid and its application to sensitive high-performance liquid chromatographic determination with fluorimetric detection

The stability of the o-phthalaldehyde (OPA) derivatives of sisomicin obtained using beta-mercaptopropionic acid was investigated by reversed-phase high-performance liquid chromatography. One of the fluorescent derivatives of sisomicin was stable at least for 6 h in 50% methanol under the optimal conditions used (OPA concentration, pH and temperature). When plasma samples spiked with sisomicin were analysed, the response was linear in the calibration range 136-900 pg of sisomicin per injected volume (40 microliters). As little as 0.06 micrograms of sisomicin per 1 ml of plasma could be detected with signal-to-noise ratio greater than or equal to 2. For plasma samples spiked with 0.2 micrograms/ml sisomicin, the recovery was 97.1 +/- 6.6% (mean +/- S.D., n = 5) with a within-run coefficient of variation of 6.8% and a day-to-day coefficient of variation of 7.2%. The method was also applied to plasma samples from rabbit after a subcutaneous injection of 1 mg/kg sisomicin.

[Dependence of the antimicrobial effect on the antibiotic concentration in modelling pharmacokinetic profiles in vitro: a comparison of 2 regimens for the single intravenous administration of sisomicin]

Kinetics of sisomicin antimicrobial effect on E. coli was studied in an in vitro dynamic model. Pharmacokinetic profiles observed in blood of humans treated with different polar dosing schedules i. e. bolus administration and continuous infusion were simulated. The first set of the experiments included simulating the profiles observed at short-term maintenance (0.25-20 min) of relatively high antibiotic levels after bolus administration (Cmax = 0.125-10 micrograms/ml). The second set included simulating the profiles observed at long-term maintenance (1-15 hours) of relatively low antibiotic levels after infusion (Cmax = 0.125-1.75 micrograms/ml). Changes in the viable count in the dynamic model were estimated microcolorimetrically with BioActivity Monitor LKB 2277-202. The use of the recently developed parameters of antimicrobial effect intensity IE and duration TE provided determination of relationship between IE or TE and logarithm of the area under the concentration-time curve (lg AUC). Its own IE (or TE) vs lg AUC curve including 4 phases corresponded to every administration schedule i. e. bolus and infusion. The 1st and 3rd phases reflected weak changes in IE or TE at significant increasing of the AUC and the 2nd and 4th phases reflected a marked increase in IE or TE at insignificant changing of the AUC.(ABSTRACT TRUNCATED AT 250 WORDS)

Ceftazidime monotherapy vs. combined therapy in Pseudomonas pulmonary infections in cystic fibrosis

To evaluate whether the addition of an aminoglycoside might enhance the clinical efficacy of ceftazidime in cystic fibrosis patients with acute exacerbations of chronic Pseudomonas lung infections we carried out a prospective, comparative, randomized blind study with three schedules: ceftazidime vs. ceftazidime plus sisomicin (C/S) vs. piperacillin plus sisomicin, for a total of 60 courses of 14 days of treatment. Each treatment led to clinical and radiologic improvement with marked reduction of signs of acute infection. Statistically there was no significant difference in clinical responses among the schedules. No side effect appeared during treatments with ceftazidime or C/S. Hyperpyrexia was seen in 35% of patients receiving piperacillin. Decrease in Pseudomonas aeruginosa count to less than 10(5) colony-forming units/ml of sputum was achieved in 60% of patients treated with C/S and in 30% of patients who received ceftazidime or piperacillin plus sisomicin (statistically not significant). A transient increase in mean geometric minimal inhibitory concentrations for ceftazidime and piperacillin was observed at the end of the combined therapies. A larger percentage of persistent resistant strains of P. aeruginosa was seen after the combined therapies. We conclude that ceftazidime as monotherapy may be an effective alternative in Pseudomonas lung infections in cystic fibrosis patients. Its clinical efficacy seems not to be enhanced by the addition of an aminoglycoside, although reduction of Pseudomonas in the sputum was better achieved by the combination of C/S.

Human pharmacology of 5-epi-sisomicin (Sch 22591) following intramuscular administration

5-epi-sisomicin was given as a single intramuscular injection of 1 mg/kg to six healthy male adults. Serum peak concentrations averaged 3.07 mg/l, the mean elimination half life was 179 min and the mean 24 h urinary recovery was 85.3%. Local and systemic tolerance was good.

[Clinical evaluation of sisomicin in the treatment of complicated chronic urinary tract infections administered by intravenous infusion]

The pharmacokinetics of sisomicin (SISO) were determined in 3 patients including a case with mild renal dysfunction after intravenous infusion over 1 hour of a single dose of 50 mg. The peak serum concentration was ranged from 3.3 to 3.9 micrograms/ml with about 2 hours of half-life in patients with normal renal function and 4.5 hours in a patient with renal impaired function. This result suggested that dosage regimen should be adjusted in patients with renal impaired function. Clinical response was evaluated in treatment of 16 cases with chronic complicated UTI. SISO was administered intravenously over 1 or 1.5 hours at a daily dose of 100 or 150 mg. An overall excellent or moderate effect was seen in 68.8% of treatment cases with the evaluation by the UTI committee's criteria. As for clinical laboratory abnormal values, a slight but reversible increase of BUN was observed in 1 case. In conclusion, intravenous administration of SISO appeared to be effective and useful method for treatment of complicated UTI.

Serum concentration of sisomicin by intravenous infusion and its clinical response as a single agent

SISO in doses of 1.0 to 1.8 mg/kg was administered by a 30-minute intravenous infusion every 12 hours to 10 patients with infections, 9 of whom had underlying diseases including malignant diseases, diabetes mellitus, and diabetes insipidus with indwelling FOLEY catheter. The serum concentration of SISO was around 6.75 micrograms/ml in the end of infusion, and less than 1.0 micrograms/ml at 8 to 12 hours after infusion. SISO was given to the patients as a single agent for at least 3 to 5 days and all patients experienced an excellent to good response clinically, and causative organisms which showed a minimal inhibitory concentration of less than 1.56 micrograms/ml disappeared after the treatment associated with clinical improvement. There were no untoward effects noted in this study.

[In vitro study on the combined effect of mezlocillin and sisomicin on clinically pathogenic P. aeruginosa and E. coli]

Clinically pathogenic Pseudomonas aeruginosa and Escherichia coli were subjected to test in vitro combination effect of mezlocillin (MZPC) and sisomicin (SISO). The chequer board titration method, using brain heart infusion broth (BHIB, Difco), demonstrated the combination effect of MZPC and SISO on the both isolates. The bactericidal combination effects (MBCs) were clearly higher than the bacteriostatic combination effects (MICs). The bactericidal activities of combination with MZPC and SISO were tested on both P. aeruginosa and E. coli. The MZPC plus SISO of low concentrations showed the synergistic effects on both isolates.

[Clinical evaluation of sisomicin following intravenous drip infusion in respiratory tract infections]

The efficacy, safety and utility of sisomicin (SISO) followed intravenous infusion were evaluated in 35 cases with various respiratory infections. For many cases, SISO was given at a daily dosage of 100 mg, and a single dose was infused over about 1 hour. Clinical efficacy was evaluable in 28 cases including pneumonia (14 cases), bronchitis (8 cases), bronchiectasis (4 cases), pulmonary suppuration (1 case) and pulmonary abscess plus pyothorax (1 case). Almost cases had diagnosis of serious infection associated with various diseases. Clinical efficacy was evaluated as "excellent" in 2 cases, "good" in 15 cases, "fair" in 5 cases and "poor" in 6 cases, and efficacy rate in total case was 60.7%. Efficacy rate stratified by disease was calculated as 57.1% in pneumonia, 87.5% in bronchitis, 50.0% in bronchiectasis. Responses against pulmonary suppuration or pulmonary abscess with pyothorax were little or not. Bacteriologically, organisms isolated from sputum cleared in 7 out of 15 evaluable cases, thus the responses rate was 46.7%. Adverse reaction probably due to treatment observed in 2 cases with hepatic dysfunction. Blood levels of SISO at the end of infusion were ranged from 2.1 to 6.4 micrograms/ml, and no tendency of accumulation in blood after repeated infusion was showed.

[A dynamic system for the in vitro study of the kinetics of the antimicrobial effect of antibiotics in pharmacokinetic changes in their concentration]

The present approaches to in vitro investigation of the kinetics of the antibiotic antimicrobial effect are based on its recording at one or another constant concentration of the drugs. The regularities revealed under such conditions do not usually reflect the peculiar effect of the drugs in vivo, since with the use of the routine schemes of dosing the drug levels in the body fluids always vary. For investigation of the kinetics of the antimicrobial effect of antibiotics at their varying levels, a universal dynamic system providing in vitro simulation of the pharmacokinetic profiles of the drugs in blood and tissues was developed. The system is based on the controlled dilution of the medium containing an antibiotic and microbial cells. the dynamic system allows simulation of any kinetic profile of the drugs with regard to the constants of the linear pharmacokinetic N-compartmental model. The trial of the dynamic system as applied to the antimicrobial effect of sisomicin on strain A 20 363 of E. coli revealed significant differences in the effect of the drug, when its bioexponential pharmacokinetic profile was simulated in a one-compartmental model with exponential absorption and a constant concentration of the antibiotic. The check determinations of the antibiotic concentration in the main flask of the system showed that the system provided high accuracy simulation of the required antibiotic levels.

[Clinical experience of sisomicin sulfate by intravenous drip infusion for the treatment of infection complicated by malignant disease]

Sisomicin sulfate (SISO) was used for the treatment of infections complicated by malignant diseases in 10 cases; 4 cases with suspicious sepsis, 2 with pneumonia, 2 with urinary tract infection, 1 with renal abscess and 1 with cholecystitis. SISO was administered by intravenous drip infusion at daily dose from 100 to 150 mg for 6 to 12 days, concomitantly with other antibiotics. Clinical results were as follows; Good in 2, fair in 5, poor in 3 cases. As to the side effects of SISO, cylindruria with aggravation of microscopic hematuria and elevations of GOT, GPT and A1-P were observed each one of them, respectively. The relationship to the SISO, however, was not clear. In view of the above results, the drip infusion of SISO may be useful for the treatment of serious infection complicated by malignant diseases.

[A pharmacokinetic investigation of sisomicin administered intramuscularly to children]

For the purpose of studying the pharmacokinetic profile of sisomicin (SISO) and the proper conditions for its administration to children, SISO was administered intramuscularly to 10 infants aged less than 1 year, 16 young children and 18 school children at doses of 1.0, 1.5 and 2.0 mg/kg and its serum and urine levels were determined by bioassay. The mean peak levels of SISO in serum appeared at 1/4 hour in the infants, irrespective of the dose; the mean peak levels were 2.27, 3.05 and 4.83 micrograms/ml after the 1.0, 1.5 and 2.0 mg/kg doses, respectively. In the young children, the mean peak levels appeared at 1/4 hour after the 1.0 mg/kg dose and at 1/2 hour after both the 1.5 mg/kg and 2.0 mg/kg doses. The mean peak levels were 2.82, 3.80 and 6.43 micrograms/ml, respectively. In the school children, the mean peak levels appeared at 1/2 hour after all the doses and were 4.34, 5.31 and 6.87 micrograms/ml, respectively. The mean peak levels were in the order of school children greater than young children greater than infants and were dose-dependent. In the infants, the mean urinary recovery was 43.7% for the 1.0 mg/kg dose and 31.2% for the 1.5 mg/kg dose; in the young children, 50.5, 35.9 and 65.6% for the 1.0, 1.5 and 2.0 mg/kg doses, respectively; and in the school children, 54.2, 50.2 and 56.7%. Using the observed serum levels, the pharmacokinetic parameters were calculated according to the one-compartment open model theory. (1) The mean elimination rate constants (K) were calculated at 0.60, 0.67 and 0.56 hr-1 for the infants, young children and school children, respectively. There were found no great differences among the above 3 age groups. The mean absorption rate constants (ka) were 18.5, 7.6 and 5.9 hr-1 and the apparent volumes of distribution per kg body weight, Vd (L/kg), 0.44, 0.26 and 0.22 L/kg, respectively. These 2 parameters were significantly greater in the infants than in the young children and school children. The maximum serum concentration (Cmax) and the time when the concentration reaches a maximum (Tmax) were substantially in agreement with the observed values. The half-lives (T1/2) were 1.16, 1.03 and 1.23 hours for infants, young children and school children, respectively, and did not differ significantly among the 3 groups. A serum level simulation curve constructed by plotting the mean values for K, ka and Vd did not reveal any substantial deviation from the observed values.(ABSTRACT TRUNCATED AT 400 WORDS)

[Aerosol administration of dibekacin--the sputum concentration]

Serum concentrations of dibekacin (DKB), sisomicin (SISO) and gentamicin (GM) were measured in 3 rabbits after intratracheal administration through the transtracheal teflon tube. The peak serum levels (average) were 106 micrograms/ml (administrated 100 mg DKB for injection), 148 micrograms/ml (administrated 100 mg DKB solution), 166 micrograms/ml (administrated 100 mg SISO solution) and 80 micrograms/ml (administrated 80 mg GM solution). Serum concentrations and urine excretions of DKB were measured in 3 volunteers after aerosol administration using ultrasonic nebulizer. The peak serum levels (average) were 4.6 micrograms/ml (administrated 100 mg DKB for injection) and 3.1 micrograms/ml (administrated 100 mg DKB solution). The urine excretions (average) were 3.7 mg and 4.3 mg respectively during 6 hours. Before and after administration of DKB aerosol the spirogram and flow-volume curve were examined in the volunteers. But the examinations showed no changes. Sputum concentrations were measured in 1 patient with chronic bronchobronchiolitis after administration of DKB aerosols using the ultrasonic nebulizer. The highest sputum concentration was acquired immediately after nebulization and the sputum levels decreased gradually while time passed. Six patients with the lower respiratory tract infections were treated with DKB aerosol therapy and the utility rate was 80%.

[Simulation of the pharmacokinetics of aminoglycosides in the kidneys: single and continuous intake of sisomicin and gentamicin by rats]

The pharmacokinetics of sisomicin and gentamicin in the cortical and medullary layers of the kidneys was studied on rats. The antibiotics were administered daily in doses of 12.5 and 25 mg/kg a day. The levels of the antibiotics in the cortical layer were much higher than those in the medullary layer. The use of a twice as higher dose in the first case resulted in a less than a two-fold increase in the drug concentration, while in the second case the increase was more than two-fold. Prognosis of the pharmacokinetics of aminoglycosides used for 8-16 days was achieved with the help of the constants of the two-compartmental model. It was shown that the actual levels of sisomicin and gentamicin in the kidney medullary layer did not significantly differ from the estimated ones and the levels of the drugs in the cortical layer were much lower than the predicted ones. The distorted linearity of the aminoglycoside pharmacokinetics must be mainly due to saturation of the cortical layer with the drugs.

[Pharmacokinetic prediction of the efficacy of using sisomicin in wound infections]

The pharmacokinetics of sisomicin in the blood, infection foci and urine of patients with wound infections was studied comparatively. Higher blood levels of the antibiotic after intravenous injection as compared to those after intramuscular injection provided its more intensive penetration into the tissues of the wound edges and bottom. After intravenous injection the sisomicin concentration in the tissues was sufficient for inhibition of the strains of Staphylococcus, E. coli and Ps. aeruginosa detected in the patients, while after intramuscular injection the antibiotic levels were sufficient only for inhibition of the first two causative agents. Comparison of the data on the sisomicin pharmacokinetics in the blood and tissues of the wounds provided the characteristics of the level of the drug penetration into the focus of the infection ("therapeutic availability"). Since the levels of sisomicin in the blood and infection foci were highly variable in different individuals. It is recommended that the antibiotic be used under the control of its concentrations in patients. It was shown that the data on the sisomicin renal excretion might be used for the purposes of the pharmacokinetic control.

[Pharmacokinetic basis for using tobramycin and sisomicin in treating pyelonephritis of the transplanted kidney]

The pharmacokinetics of tobramycin and sisomicin in patients after kidney transplantations was studied. A significant variability of the pharmacokinetic parameters of tobramycin and sisomicin under conditions of the changing function of the kidney transplant was shown. This required individual control of the drug serum levels in such patients. Linear correlation between the exponent (beta) and the clearance of endogenous creatinine was observed. On the basis of this correlation a nomogram providing a decrease in the percentage of the errors in determining the dosage intervals was plotted.

[Studies on the combination action of sisomicin, gentamicin and piperacillin, cefmetazole against Pseudomonas aeruginosa and Serratia marcescens]

The combined actions of sisomicin (SISO), gentamicin (GM) and piperacillin (PIPC), cefmetazole (CMZ) against Pseudomonas aeruginosa E-2 and Serratia marcescens T-55 were studied. The following results were obtained. 1. The combinations of SISO-PIPC, SISO-CMZ, GM-PIPC and GM-CMZ using the checker board dilution method on P. aeruginosa E-2 and S. marcescens T-55 were found to have a synergistic effect and the minimum FIC index values were 0.38 in all combinations. 2. With the killing kinetic method, all combinations tested showed a synergistic effect. 3. A synergistic effect of the combinations of SISO-PIPC, SISO-CMZ, GM-PIPC and GM-CMZ was observed in the protective effect on experimental P. aeruginosa E-2 and S. marcescens T-55 infections in mice.

[Build up of a given concentration of tobramycin and sisomycin in the blood of young children by the intravenous infusion of the antibiotics according to a calculated regimen]

Three regimens for intravenous infusion of tobramycin and sisomicin in doses of 1.33 and 1 mg/kg, respectively were analysed theoretically with the use of the constants of a two-compartmental model characterizing the tobramycin pharmacokinetics in adults. The regimen implied administration of the antibiotics by means of a 12-hour infusion. The second regimen consisted of a jet injection of the initial dose simultaneously with the beginning of the maintenance infusion. The third regimen consisted of a rapid initial infusion followed by a slow maintenance infusion. It was shown that maintenance of the drug concentration at the required levels, i.e. 2-8 microgram/ml for tobramycin and 2-61 microgram/ml for sisomicin was most safely provided by the regimen of the subsequent infusions. This regimen was tried clinically in the treatment of 17 children aged 2 months to 2.5 years with severe forms of acute pneumonia. The rate of the 25-minute initial infusion of tobramycin was 22.2 microgram/kg . min and that of the subsequent 2.7-hour maintenance infusion was 4.85 microgram/kg . min, the total dose being 1.33 mg/kg. The rate of the 20-minute initial infusion of sisomicin was 21.7 microgram/kg . min and that of the subsequent 2.4-hour maintenance infusion was 3.88 microgram/kg . min, the total dose being 1 mg/kg. It was shown that the levels of both the antibiotics in the blood serum of the patients were within the required ranges.

[Pharmacokinetics of a cefotetan and an aminoglycoside preparation in combined administration. 2. Absorption and exercise of cefotetan and sisomicin in dogs when the two are given together]

Cefotetan (20 mg/kg i.v.) and sisomicin (10 mg/kg i.m.) were administered alone or in combination to Beagle dogs. The mean plasma concentrations of cefotetan administered in combination with sisomicin at the above dosages were 98.0 microgram/ml at 5 minutes, 45.7 microgram/ml at 30 minutes and 3.46 microgram/ml at 4 hours. These plasma concentrations of cefotetan were similar to those of cefotetan administered alone to the corresponding dogs. The calculated plasma half-lives (T 1/2 beta) of cefotetan were 53.9 minutes in combination with sisomicin and 57.4 minutes alone. The excretion of cefotetan in dog urine were 52.4% and 50.2% of the dose after administration in combination with sisomicin and alone, respectively, during 24 hours. The results indicate that there were no significant differences in the pharmacokinetics of cefotetan alone or in combination with sisomicin in dogs. The maximum concentrations of sisomicin in dogs administered in combination with cefotetan were 20.2 microgram/ml at 30 minutes after dosing. The concentrations of 11.7 microgram/ml at 2 hours and 3.13 microgram/ml at 4 hours of administration were maintained in plasma. The calculated plasma half-lives of sisomicin were 68.8 minutes in combination with cefotetan and 86.4 minutes alone. The urinary rcoveries of sisomicin were 79.3% and 76.1% in combination with cefotetan and alone, respectively, during 24 hours. There were no significant differences in the pharmacokinetics of sisomicin alone and in combination with cefotetan in dogs.

[Pharmacokinetics of cefotetan and an aminoglycoside preparation in combined administration. 1. Individual quantification of cefotetan and sisomicin by bioassay and their absorption, distribution, and excretion in rats when given together]

The beta-lactam and aminoglycoside groups of antibiotics are often used in combination. This paper reports a bioassay method for each of cefotetan and sisomicin concentration in body fluids, and pharmacokinetics of both drugs following intravenous administration of cefotetan and intramuscular administration of sisomicin alone and in combination to rats. As to cefotetan determination, a previously reported bioassay method was modified by increasing the NaCl concentration in the sensitivity test agar from 0 to 6%, using Bacillus subtilis ATCC 6633 as the test organism. To assay for sisomicin in the presence of cefotetan, Pseudomonas aeruginosa ATCC 8689, resistant to the beta-lactam antibiotic, was used. Cefotetan (20 mg/kg intravenous) and sisomicin (10 mg/kg intramuscular) were administered concomitantly to rats. The mean plasma concentrations of cefotetan and sisomicin were 16.3 microgram/ml and 16.1 microgram/ml, at 30 minutes after administration respectively. The concentrations were declined to 2.20 microgram/ml for cefotetan and 2.53 microgram/ml for sisomicin at 90 minutes after dosing administration. The calculated plasma half-lives (T 1/2 beta) were 21.3 minutes for cefotetan and 22.2 minutes for sisomicin. The plasma and tissue concentrations of cefotetan administered in combination with sisomicin were nearly the same as those of cefotetan alone. Urinary excretion of cefotetan and sisomicin in the concomitant administration was carried out in rats. Recoveries in urine were 45.9% of the dose for cefotetan and 85.6% of the dose for sisomicin for a period of 24 hours. When each drug was administered alone to rats, cefotetan and sisomicin were recovered 49.8% and 81.6%, respectively, of the dose in the 24-hour urine.

Empiric antibiotic treatment of infections in myelosuppressed cancer patients. Preliminary results

A prospective, randomized study was performed to compare the efficacy and safety of mezlocillin plus sisomicin (Regimen A) and cefamandole plus tobramycin (Regimen B). Sixty-one episodes of documented infections were treated in 49 adult myelosuppressed cancer patients. About two-thirds of the patients treated with either regimen responded to this antibacterial therapy. The patients failing to respond to the initial therapy were treated with additional antibiotics, either with the empiric Regimen C (cefotaxime plus amikacin plus azlocillin) or with antibiotics selected on the basis of bacteriological results (Regimen D). With these schedules, the over-all response rate was increased to about 90%. The data suggest that febrile granulocytopenic cancer patients may profit from this empiric and sequential antibiotic treatment.

Combined action of decreasing concentrations of azlocillin and sisomicin on Pseudomonas aeruginosa as assessed in a dynamic in vitro model

The effect of decreasing concentrations of azlocillin and sisomicin on Pseudomonas aeruginosa was examined. Logarithmically growing bacterial cultures were incubated in an ultrafiltration cell, and after adding the antibiotics, the culture medium was diluted every 20 min without any decrease in cell density. The turn-over of medium resulted in the elimination of azlocillin with a half-life of 75 min. This simulated serum kinetics in vivo. When testing sisomicin, small amounts of this agent were added during every dilution step to achieve a half-life of 120 min. Growth conditions were comparable in all experiments. The simultaneous combination of azlocillin and sisomicin resulted in strong synergism as assessed by higher killing rates and more prolonged growth inhibition of surviving bacteria. Comparable results were observed when both drugs were added at intervals of 40 min. When applied at intervals of 120 min, the combined effect of azlocillin and sisomicin was reduced, but still superior to the effect of double the concentration of each compound alone. Thus, neither pre-treatment with azlocillin nor with sisomicin impaired the antibacterial activity of the combination partner. This seems to be of clinical importance since the agents may be administered at different times during combined therapy.

[Elaboration of the procedures for the pharmacokinetic interpretation of aminoglycoside nephrotoxicity: the experimental evaluation of the safety of repeated gentamycin administration]

Nephrotoxicity and pharmacokinetics of gentamicin were studied on rats treated with the antibiotic for 30 days in doses of 6.25, 12.5 and 25 mg/kg administered daily. The pharmacokinetics of gentamicin and the time course of changes in the urea nitrogen levels of the blood serum were studied after the 1st, 5th, 8th and 30th injection. The analysis of the respective curves was used for calculation of the average integral values of the concentrations of the antibiotic (C) and urea nitrogen (E). After that the average integral values of these parameters ((CAVG and EAVG respectively) within the whole treatment couse with the use of every dose were calculated in the same way by using the curves of the dynamics of C and E changing. Comparison of the diagrams of E dependence on C for gentamicin and sisomycin showed that nephrotoxicity of sisomycin was 1.48 times higher than that of gentamicin.

Pharmacokinetic study of sisomicin in humans

Detailed analyses of the pharmacokinetics of sisomicin administered at doses of 25, 50 and 100 mg intravenously and intramuscularly to healthy volunteers established that the drug is handled by a two-compartment open model system with a disposition (elimination) half-life of 2.6 hr. The kinetic estimates over this dose range are linear and independent of dose and were verified by a 60-min infusion experiment in which dose and the maximum serum concentration achieved (5 microgram/ml) were predicted correctly. Sisomicin was rapidly distributed to the tissue compartment, and equilibrium between the central and the tissue compartment was established by 30 min after dosing. Renal clearance (55 ml/min) of sisomicin was about 30% less than total body clearance (78 ml/min). Total urinary excretion of sisomicin during a 24-hr period following drug administration was about 70% of the dose. The disposition kinetics of sisomicin following intramuscular administration are similar to those obtained following rapid intravenous administration. Intramuscular bioavailability of sisomicin for the doses of 25, 50, and 100 mg was greater than 95%. Based on these results, various initial loading infusion doses and maintenance infusion rates were calculated to provide specific desired peak and steady-state serum sisomicin concentrations rapidly. The purpose was not to expose patients to potentially toxic high peak concentrations of drug while maintaining these concentrations during the current therapeutic dosing intervals of 8 to 12 hr.

[Sisomicin pharmacokinetics in rat tissues in single and long-term administration]

The pharmacokinetics of sisomicin administered intramuscularly to rats in daily doses of 12.5 and 25 mg/kg for 30 days was studied. After a single administration of the drug in the above doses the highest and the lowest levels of sisomicin were observed in the kidney cortical layer and liver, respectively. The antibiotic level in the tissues rose with an increase in the antibiotic dose and duration of the drug use. The two-fold rise in the dose resulted in an elevation in the sisomicin level in the kidney cortical layer by 1.7 times, in the medullary layer by 3 times, and in the blood serum, lungs and spleen by 2.3, 1.2 and 1.5 times, respectively. After treatment with a dose of 25 mg/kg for 8 days the antibiotic level in all tissues studied was higher than that after the first administration of the drug: in the cortical and medullary layers of the kidneys by 5-7 times and in the blood serum and other tissues by 1.2-2 times. When sisomicin was used repeatedly in any dose, stabilization of or some decrease in the mean integral concentration of the antibiotic in the kidney cortical layer and a continuous increase of this value with respect to the medullary layer (up to the 30th day) were noted. The difference between the antibiotic levels in the kidney layers after the repeated administration of the drug was less pronounced than that after a single administration of the drug. The cumulation index of sisomicin in the kidney cortical layer persisted at the same level and that in the medullary layer gradually increased. In this connection it is concluded that correlation between the sisomicin nephrotoxic effect and the level of the antibiotic in the kidney cortical layer is more pronounced than that in the medullary layer.

[Treatment of severe febrile neutropenia (author's transl)]

Random allocation of 22 patients with benign and malignant diseases with neutrophil counts of up to 1 X 10(9)/l blood and probably infection-caused fever of more than 38 degrees C to intravenous treatment with one of the following antibiotic combinations was performed: carbenicillin (6 g/m(2) . 6 h) plus sisomicin (45 g/m2 . 6 h) or mezlocillin (3 g/m2 . 6 h) plus sisomicin (45 g/m2 . 6 h). Both combinations were tolerated equally well. Patients became afebrile in 16 out of 23 treatment periods. Seven out of 11 patients responded to carbenicillin - sisomicin, and 9 out of 12 to mezlocillin - sisomicin. Mezlocillin thus leads to equal success of treatment in febrile neutropenia as the double dose of carbenicillin when both antibiotics are combined with the same aminoglycoside.

[Pharmacokinetic basis of the nephrotoxic action of sisomycin. The pharmacokinetics of sisomycin in single and multiple administrations to rats]

The pharmacokinetics of sisomicin was studied on Wistar rats. The antibiotic was used in single or repeated doses of 12.5 and 25 mg/kg. The kinetic data of the antibiotic titration in blood serum within 1 and 24 hours of intramuscular administration of the drug were formalized with the use of a linear two-compartment model. The average values of the elimination constant and the constants of sisomycin transfer from the central compartment into the peripheral one were 0.64, 0.34 and 0.13 hours-1 respectively. The value of the apparent distribution volume in the central compartment was 0.38 ml/kg and that of the stationary and kinetic distribution volumes was 1.37 and 3.06 1/kg respectively. The value of the general clearance was 0.24 1/(kg.hour) and that of the sisomicin half-life was 8.7 hours. Comparison of the antibiotic levels estimated with a model and actually measured in the blood after repeated administrations revealed the drug cumulation. When the antibiotic was used in a dose of 25 mg/kg daily, its cumulation was observed earlier (by the 5th--8th day) than on its use in a dose of 12.5 mg/kg (by the 30th day). Irrespective of the dose, sisomicin cumulation was accompanied by prolongation of the antibiotic half-life in the rats.