Treatment of septicaemia in immunocompromised patients with ceftazidime or with tobramycin and cefuroxime, with special reference to renal effects

Fifty-two immunocompromised patients with suspected septicaemia were randomized on 61 occasions to treatment with ceftazidime or with tobramycin and cefuroxime. Most (90%) of the patients had haematological malignancies and were neutropenic (granulocytes less than 1 X 10(9)/1 in 40 of the 61 episodes). Blood cultures were positive in 22 (39%) febrile episodes and in four other instances positive cultures were obtained from other sources. Clinical cure or improvement was noted in 10 of 12 culture verified infections in the tobramycin and cefuroxime group and 11 of 14 episodes in the ceftazidime-group. The effect on the kidney of the two antibiotic regimens was studied by following the serum levels of creatinine, urea and beta 2-microglobulin and the urinary excretion of alanine aminopeptidase, N-acetyl-beta-D-glucosaminidase (beta-NAG) and beta 2-microglobulin. No clinically important renal side effects were observed. However, an increase in the urinary excretion of AAP was seen in both groups with significantly greater elevation in the tobramycin and cefuroxime group. Urinary beta-NAG increased only in the tobramycin and cefuroxime group.

Ceftazidime as prophylactic treatment in renal stone surgery. Clinical evaluation and pharmacokinetics in renal tissue

The effect of ceftazidime in surgery of renal stones associated with urinary tract infection was investigated and its pharmacokinetics in serum and renal tissue was compared in 14 patients (15 kidneys) operated on for renal calculi associated with multiple urinary tract infection. Two to four days preoperatively ureteric catheterization was performed to localize the level of the infection and 2 g of ceftazidime was given intravenously twice daily for 10 days. Renal biopsy, serum samples and in one patient renal lymphatic fluid were taken simultaneously for antibiotic assay. Urine cultures were performed at regular intervals pre- and postoperatively. Ten patients had bacterial growth in the stone-carrying renal pelvis. The same strain was found in the bladder as in the pelvis. Nine patients had sterile urine after 3-5 days of treatment. One patient with bilateral stones did not get sterile urine until after seven days of treatment. Bacterial growth was found in two out of six cultured stones obtained from patients with bacterial growth in the pelvis. The decreases in concentration of ceftazidime in serum and renal tissue seemed to be parallel. Slight reversible elevation of liver transaminases was noted in 5/14 patients. It is concluded that the concentration of ceftazidime in serum parallels that in renal tissue. Ceftazidime seems to be an effective prophylactic in renal stone surgery and the preoperative dose should be given close to the operation.

Penetration of ceftazidime into the rabbit respiratory tract

A procedure is described for the direct collection of bronchial or tracheal fluid samples on to paper discs. Using the procedure, the pharmacokinetics of ceftazidime in rabbit bronchial and tracheal fluids were compared with those in the respective wall tissue samples and in lung tissue. Concentrations appearing in lung tissue were approximately half those seen in bronchial or tracheal fluid or bronchial and tracheal wall tissue. Concentrations in these latter compartments were, in turn, four- to six-fold lower at all times than simultaneously-measured serum levels. The shape of the concentration/time curves were similar for all compartments sampled. The half life values were 63 to 64 min for respiratory tract concentrations and 59 min for serum levels. Percentage penetration from serum into the various compartments was 20.8% for bronchial fluid, 19.9% for tracheal fluid, 22.4% for bronchial wall, 20.0% for tracheal wall and 11.3% for lung tissue.

Efficacy of ciprofloxacin in experimental aortic valve endocarditis caused by a multiply beta-lactam-resistant variant of Pseudomonas aeruginosa stably derepressed for beta-lactamase production

The emergence of multi-beta-lactam resistance is a limiting factor in treating invasive Pseudomonas infections with newer cephalosporins. The in vivo efficacy of ciprofloxacin, a new carboxy-quinolone, was evaluated in experimental aortic valve endocarditis caused by a strain of Pseudomonas aeruginosa which is stably derepressed for beta-lactamase production and is resistant to ceftazidime and multiple other beta-lactam agents. A total of 51 catheterized rabbits with aortic catheters in place were infected with this strain and then received no therapy (controls), ceftazidime (75 mg/kg per day), or ciprofloxacin (80 mg/kg per day). Ciprofloxacin sterilized all blood cultures and significantly lowered vegetation densities of P. aeruginosa by day 2 of treatment versus controls (P less than 0.0005) and animals receiving ceftazidime (P less than 0.0005). This beneficial effect of ciprofloxacin was also noted on therapy days 6 and 11. Ciprofloxacin rendered most vegetations (85%) culture negative over the 11-day treatment period and achieved bacteriologic cure in 73% of animals (P less than 0.0005 versus other therapy groups). Ciprofloxacin prevented bacteriologic relapse at 6 days posttherapy. No ciprofloxacin resistance was detected among Pseudomonas isolates from cardiac vegetations. Ciprofloxacin warrants further evaluation in vivo versus multi-drug-resistant gram-negative bacillary infections.

Dosage adjustment for ceftazidime in patients with impaired renal function

Ceftazidime has good antibacterial activity against many Gram-negative micro-organisms including Ps. aeruginosa. The aim of the present study was to calculate a dosage adjustment regimen for renal failure patients and to test it in a second group of patients. A study was made of the pharmacokinetics of ceftazidime 1 g given as a single bolus i.v. injection in 20 patients in an intensive care unit with varying degrees of renal function, including patients on regular haemodialysis. The serum half-life of elimination (t1/2 beta) varied from 1.6 to 45 h depending on renal function. During haemodialysis the mean t1/2 was 4.7 h. A good correlation between the renal clearance of creatinine and ceftazidime was observed. In most patients protein binding was lower than previously observed. From the pharmacokinetic data, a dosage adjustment regimen for patients with renal insufficiency was calculated, which studies in 7 further patients showed to be effective.

[Pharmacokinetic studies on ceftazidime in neonates]

The pharmacokinetics of ceftazidime (CAZ) were investigated in neonates. The following was a summary of the results obtained. Mean peak serum levels of CAZ reached at 15 minutes after intravenous administrations at single doses of 10 mg/kg were 31.7 micrograms/ml in 1-day-old neonates and 31.4 micrograms/ml in a 13-day-old neonate. Mean serum levels at 6 hours after administrations were 8.97 micrograms/ml and 5.26 micrograms/ml in the 1-day-old and the 13-day-old, respectively. Mean half-lives of CAZ in sera were 3.29 hours in the 1-day-old and 2.24 hours in the 13-day-old. In a 4-day-old neonate, the serum level of CAZ reached a peak of 25.4 micrograms/ml at 1 hour and was 5.75 micrograms/ml at 6 hours; the half-life was 2.41 hours. Peak serum levels of CAZ reached at 15 minutes after intravenous administrations at single doses of 20 mg/kg were 46.3 micrograms/ml in a 3-day-old neonate and 80.6 micrograms/ml in a 7-day-old neonate. The serum levels at 6 hours after administration were 12.2 micrograms/ml and 10.4 micrograms/ml, in the 3-day-old and the 7-day-old, respectively. Half-lives of CAZ in sera were 3.02 hours in the 3-day-old and 2.08 hours in the 7-day-old. In 4-day-old neonates, mean serum levels were 52.5 micrograms/ml at 15 minutes and 14.6 micrograms/ml at 6 hours after administration and the half-life was 2.76 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical evaluation of ceftazidime in the treatment of neonatal infections]

Ceftazidime (CAZ) was evaluated for its safety and efficacy in 27 newborns. Four confirmed cases of bacterial infections were cured by the CAZ therapy (efficacy rate 100%). The CAZ was assessed as effective in sepsis (2) and urinary tract infections (2). Main pathogens which responded to CAZ were Escherichia coli, Enterobacter cloacae and Acinetobacter anitratum. As adverse effects, elevations of GOT and GPT (1 case) were found to be associated with the CAZ therapy. Half-lives of the serum levels in mature infants were 1.93-3.52 hours, and those in low birth weight infants were 2.92-4.17 hours. Penetration into the cerebrospinal fluid in 1 case of viral meningitis was satisfactory. The data suggest that CAZ is a safe and effective injectable antibiotic when used in newborn with infection caused by CAZ-susceptible bacteria.

Treatment of bacterial meningitis with ceftazidime

Ceftazidime was prospectively evaluated in the treatment of bacterial meningitis in 19 pediatric patients. Haemophilus influenzae type b (HIB) was the etiologic agent in 17 patients, and Streptococcus pneumonia and Neisseria meningitidis were the etiologic agents in one patient each. Ceftazidime was administered intravenously in a dosage of 150 mg/kg/day divided into eight hourly doses for a mean of 15 days (range, 14 to 22 days) for H. influenzae type b meningitis. The clinical and microbiologic response was appropriate in all cases. The mean ceftazidime CSF concentration was 6.7 micrograms/ml at approximately 2 hours following iv infusions. This concentration was 16- to greater than 100-fold the minimal bactericidal concentration determined for the isolated pathogens. These preliminary observations support ceftazidime as a candidate cephalosporin for the treatment of bacterial meningitis caused by H. influenzae. Additional study is required to further define its role in meningitis caused by S. pneumoniae and N. meningitidis.

Serum bactericidal activity and killing rate for volunteers receiving imipenem, imipenem plus amikacin, and ceftazidime plus amikacin against Pseudomonas aeruginosa

Serum bactericidal activity against 20 strains of Pseudomonas aeruginosa was studied in 10 volunteers after administration of imipenem (25 mg/kg), imipenem (25 mg/kg) plus amikacin (7.5 mg/kg), and ceftazidime (25 mg/kg) plus amikacin (7.5 mg/kg). Eight strains were susceptible and 12 were resistant to ticarcillin. Serum levels were measured microbiologically after 30 and 60 min and were, respectively, 97 and 46 micrograms/ml for imipenem given alone and 79 and 45 micrograms/ml for imipenem given with amikacin. Despite the very large dose of imipenem used, imipenem and imipenem plus amikacin appeared slightly less active than ceftazidime plus amikacin (P less than or equal to 0.1; Wilcoxon matched-pairs test), with respective median titers at 30 min of 1:128, 1:128, and 1:256 against ticarcillin-susceptible strains and 1:32, 1:32, and 1:64 against ticarcillin-resistant strains; however, more than 90% of the serum determinations, regardless of the regimen, had a serum bactericidal activity greater than or equal to 1:8. Amikacin significantly increased the rate of killing in serum of P. aeruginosa by imipenem. Imipenem plus amikacin appeared as effective as ceftazidime plus amikacin in reducing the viable counts of P. aeruginosa after 24 h of incubation.

Empiric antimicrobial therapy with aztreonam or ceftazidime in gram-negative septicemia

In an open, comparative study, 225 patients with severe underlying diseases and suspected gram-negative bacillary septicemia were randomly assigned to receive aztreonam or ceftazidime empirically, 2 g intravenously three times daily. Twenty-five patients in the aztreonam group and 22 in the ceftazidime group had blood cultures that grew aerobic gram-negative bacilli and were evaluable for response to therapy. All pathogenic strains were sensitive to treatment. In the aztreonam group, 22 (88 percent) patients had cures, three (12 percent) had failures, and seven (28 percent) had development of superinfections (five were caused by gram-positive cocci and two by fungi). In the ceftazidime group, 18 (82 percent) patients had cures, one had improvement, three (14 percent) had failures, and three had superinfections. The median peak serum bactericidal activity was 1:2,048 after aztreonam administration and 1:512 after ceftazidime administration. Failures were not related to resistant strains or to low serum bactericidal activity.

Serum bactericidal activity of mezlocillin, ceftazidime, mezlocillin/ceftazidime and mezlocillin/amikacin against Klebsiella pneumoniae and Pseudomonas aeruginosa

Sera of volunteers receiving 1 g mezlocillin, 5 g mezlocillin, 1 g ceftazidime, 3 g ceftazidime, 1 g mezlocillin plus 1 g ceftazidime, and 1 g mezlocillin plus 500 mg amikacin, respectively, were evaluated for bactericidal activity against clinical isolates of Klebsiella pneumoniae and Pseudomonas aeruginosa. The titers of bactericidal activity against Klebsiella pneumoniae in serum from subjects receiving ceftazidime were higher than with other regimens both one and six hours after administration. Peak titers of bactericidal activity greater than or equal to 1:8 were also achieved more often against Pseudomonas aeruginosa in sera from subjects receiving ceftazidime than with other regimens. Killing studies confirmed these results. Although the checkerboard technique indicated synergism with the combination mezlocillin plus amikacin in vitro, this was not confirmed in vivo. Single drug therapy with ceftazidime was superior to the tested combinations.

Evaluation of novel antipseudomonal drugs using the serum bactericidal activity test

Serum bactericidal activity against Pseudomonas aeruginosa was determined in six volunteers 1 and 4 h after administration of 2 g ceftazidime, 4 g piperacillin, 500 mg imipenem, 80 mg tobramycin and four combinations of these agents. Ceftazidime produced the highest serum bactericidal titers, killing 100% and 86% of the 50 Pseudomonas aeruginosa strains tested after 1 and 4 h respectively at a serum dilution of 1:8. Imipenem had lower serum bactericidal titers than ceftazidime, killing 88% of the isolates after 1 h at a serum dilution of 1:8. The combination showed only slightly higher titers. Killing curves were determined for nine strains of Pseudomonas aeruginosa using undiluted volunteer serum drawn 1 h after administration of the antibiotics. The combinations ceftazidime/tobramycin and piperacillin/tobramycin exhibited higher killing activity than the single drugs. As the activity of the aminoglycosides could be underestimated on the basis of their low serum bactericidal titers, it is concluded that determination of these titers is inappropriate for evaluating the efficacy of the aminoglycosides.

Susceptibility of gram-negative bacteria to the synergistic bactericidal action of serum and polymyxin B nonapeptide

Polymyxin B nonapeptide was able to sensitize Escherichia coli strains and strains of Salmonella typhimurium, Klebsiella spp., Enterobacter cloacae, Pseudomonas aeruginosa, and Haemophilus influenzae to the bactericidal action of fresh normal human serum. The degree of sensitization varied significantly within the strains. Strains of Proteus mirabilis, Neisseria gonorrhoeae, and N. meningitidis remained resistant.

Comparative activities of piperacillin, ceftazidime, and amikacin, alone and in all possible combinations, against experimental Pseudomonas aeruginosa infections in neutropenic rats

This study compared the efficacy of therapy with the double beta-lactam combination of ceftazidime plus piperacillin with that of single-agent therapy with ceftazidime, piperacillin, or amikacin alone and with that of two aminoglycoside-beta-lactam combinations against Pseudomonas aeruginosa peritonitis and bacteremia in neutropenic rats. Rats made severely granulocytopenic with cyclophosphamide became bacteremic secondary to peritonitis which was induced by intraperitoneal challenge with P. aeruginosa. Antibiotic therapy with single agents (amikacin, 20 mg/kg of body weight, intramuscularly; ceftazidime, 20 mg/kg of body weight, subcutaneously; piperacillin, 200 mg/kg of body weight, intramuscularly) or with the various combinations of agents was begun 2 h after bacterial challenge and was continued every 6 to 8 h for 62 h. Therapeutic efficacy was judged on the basis of survival 72 h after bacterial challenge, rate of mortality, incidence of bacteremia, and the emergence of resistant organisms. Based on these criteria, therapy with the double beta-lactam combination had no advantage over single-agent therapy and was in all cases clearly inferior to beta-lactam-aminoglycoside combinations.

Efficacy of amikacin and ceftazidime in experimental aortic valve endocarditis due to Pseudomonas aeruginosa

The in vivo efficacies of amikacin, ceftazidime, and their combination were evaluated in experimental aortic valve endocarditis due to Pseudomonas aeruginosa. Eighty catheterized rabbits were infected with a P. aeruginosa strain susceptible to both amikacin and ceftazidime and then received no therapy (controls), amikacin (15 mg/kg per day), ceftazidime (100 mg/kg per day), or amikacin-ceftazidime. Amikacin-ceftazidime significantly lowered vegetation titers of P. aeruginosa at day 7 of therapy versus other regimens (P less than 0.0005). However, by day 14 of therapy, vegetation titers in animals receiving amikacin or ceftazidime regimens or both were not different from those of untreated controls; this was associated with in vivo development of amikacin resistance in most infected vegetations (79%), a phenomenon not seen at day 7 of therapy. Amikacin resistance was unstable in vivo, being undetectable in vegetations examined 5 days after treatment with amikacin had been completed. In contrast, ceftazidime resistance (first noted at day 7 of therapy in 12% of vegetations) persisted after termination of treatment with this agent. These in vivo observations on loss of amikacin resistance and persistence of ceftazidime resistance were mirrored during in vitro passage studies of amikacin- or ceftazidime-resistant P. aeruginosa strains isolated from cardiac vegetations. Amikacin resistance was no longer detectable by passage 5 in antibiotic-free media; however, ceftazidime resistance was stable despite 15 such passages. In vivo development of aminoglycoside-beta-lactam resistances was associated with poor bacteriologic efficacy in this model.

Serum bactericidal activity of ceftazidime increased by netilmicin

Cephalosporins are often used in combination with aminoglycoside antibiotics in the treatment of gram-negative infections. Although ceftazidime possesses activity against gram-negative bacteria, especially against Pseudomonas, combined use with aminoglycosides is useful. In this study, 12 healthy volunteers (6 men, 6 women; mean age 21.5 yr) received a single dose of ceftazidime 1 g iv and one week later ceftazidime 1 g iv with netilmicin 100 mg iv. Both antibiotics were infused over five minutes. Concentrations of ceftazidime were determined by high performance liquid chromatography. Serum bactericidal activity (SBA) was evaluated against seven microorganisms isolated from clinical specimens. The mean peak serum level of ceftazidime was 113.4 micrograms/ml. At eight hours, we observed a concentration of 2.6 micrograms/ml. The total clearance was 126 ml/min, while the renal clearance was 100 ml/min. Ceftazidime exhibited a half-life of 1.9 hours. Up to ten hours, the SBA of ceftazidime against Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, and Salmonella typhi was greater than 1:8 in more than 90 percent of samples. At one hour, ceftazidime exhibited a SBA of 1:4 for Staphylococcus aureus, and 1:16 for Pseudomonas aeruginosa. With the addition of netilmicin, median SBA against Staph. aureus and P. aeruginosa were 1:32 and 1:64, respectively, at one hour. Netilmicin enhanced the SBA of ceftazidime. The combination was not effective against Streptococcus faecalis.

Pharmacokinetic study of ceftazidime in bone and serum of patients undergoing hip and knee arthroplasty

Twenty-eight patients undergoing hip arthroplasty and 15 undergoing knee arthroplasty, received chemoprophylaxis with ceftazidime 1.0 g administered intravenously at the time of induction of anaesthesia, followed by two doses of 500 mg given intramuscularly 6 and 12 h later. The mean bone concentration in hip arthroplasty showed a general rise towards a maximum of approximately 20 mg/kg when the exposure time (interval between antibiotic injection and removal of bone sample) was 35-40 min, with values ranging from 4.4 to 21.2 mg/kg (mean 14.4 mg/kg). The patients undergoing knee arthroplasty present a complicated pharmacokinetic problem, as the use of a tourniquet limits the exposure time. Bone concentrations of ceftazidime were highest at sampling times greater than 20 min in these patients (mean level of 15.9 mg/kg for femoral bone and 13.1 mg/kg for tibial bone).

Ceftazidime as first-line therapy for fever in acute leukaemia

Fifty patients with acute non-lymphocytic leukaemia were treated by random allocation with either ceftazidime alone or a combination of piperacillin, netilmicin and cefotaxime for 65 febrile neutropenic episodes. Nineteen of 33 patient episodes (58%) responded to ceftazidime alone compared with 21 of 32 episodes (66%) treated with the combination. There was one infective death in a patient given the combination; rates of documented superinfection were low. The treatment groups appeared identical in terms of patient demography, underlying disease and other risk factors, though patients with a clinical site of infection responded more slowly than those without. Bacteraemia per se did not appear to influence outcome. Bactericidal serum concentrations greater than or equal to 8 X the minimum bactericidal concentration were predictive of a rapid response (within 4 days) to antibiotics. Furthermore, serum from patients treated with ceftazidime maintained adequate cidal activity against Pseudomonas aeruginosa for longer than that obtained from patients treated with the three-drug combination. Ceftazidime was shown to be a safe and effective alternative to the three-drug combination for the initial management of febrile neutropenic episodes in leukaemic patients.

The penetration of ceftazidime into peritoneal fluid in patients undergoing elective abdominal surgery

Using paper discs we have made repeated observations during laparotomy in 31 patients after giving 1 g of ceftazidime intravenously. Samples of serum were obtained simultaneously. Rapid transfer of antibiotic occurred. Peak concentration in peritoneal fluid occurred within 10 minutes of injection (66.7 mg/l, S.E. +/- 10.6), the concurrent mean serum level being 106.0 mg/l (S.E. +/- 10.7). Thereafter levels in serum and peritoneal fluid fell roughly in parallel.

Therapeutic efficacy of continuous versus intermittent administration of ceftazidime in an experimental Klebsiella pneumoniae pneumonia in rats

An experimental Klebsiella pneumoniae pneumonia in rats was used to study the influence of continuous or of intermittent (8-hr intervals) administration of ceftazidime on therapeutic efficacy. Antimicrobial response was evaluated with respect to the calculated total daily dose that protected 50% of the animals from death (PD50) until 16 days after termination of a four-day treatment. When antibiotic treatment was started 5 hr after bacterial inoculation, the PD50 values after continuous and after intermittent administration of ceftazidime were 0.36 and 1.42 mg/kg per day, respectively (P less than .001). With a delay in the administration of the antibiotic to 34 hr after inoculation, the respective PD50 values were 1.08 and 13.06 mg of ceftazidime/kg per day (P less than .001). These studies show an improved therapeutic efficacy that increased with a delay in treatment when ceftazidime was administered by continuous infusion as compared with administration at 8-hr intervals. Continuous administration of PD50 doses of ceftazidime resulted in serum levels that were constantly below the MIC of the infecting Klebsiella strain.

[Ceftazidime absorption into bronchial secretions in mucoviscidosis patients]

Penetration of ceftazidime into bronchial secretions was studied in 23 patients, of which 18 had cystic fibrosis. Ceftazidime was used as the single drug for treating exacerbations caused by Pseudomonas aeruginosa. Dosage was 6 g/1.73 m2/day divided into three intravenous injections for 14 to 21 days. Bronchial secretion samples were obtained by fiber-optic bronchoscopy or physical therapy. Serum and bronchial secretion ceftazidime concentrations were assayed using a microbiological method. Ceftazidime concentrations in both media were lower in children than in adults : elimination half-life is shorter (1.7 h against 2.45 h in adults), extravascular distribution is faster, with earlier (1 h against 2 h in adults) achievement of the peak bronchial secretion concentration (2 micrograms/ml). The ratio of bronchial secretion concentration to concomitant serum concentration did not exceed 5% at the time of peak bronchial concentration. These results suggest that in cystic fibrosis patients, the faster and lower bronchial penetration of ceftazidime may be due to faster elimination as compared to adults. Although transient elimination of Pseudomonas aeruginosa was achieved in 12 study patients, our findings support the use of higher dosages or alternative administration modalities designed to increase in situ ceftazidime concentrations.

Serum bactericidal activity as a therapeutic guide in severely granulocytopenic patients with gram-negative septicemia

The peak and trough levels of bactericidal activity of the serum of 74 severely granulocytopenic patients (less than or equal to 500 polymorphonucleates per microliter) with hematologic malignancies and Gram-negative septicemia were measured using the patient's infectious organism and serum containing the given antibiotics. When the peak titer of bactericidal activity in the serum was greater than 1:8 the septicemia was cured in more than 90% of the cases. However, in order to achieve a satisfactory rate of cure, patients with less than 100 polymorphonucleates/microliter required higher peak levels than patients with 100-500 polymorphonucleates/microliter. Serum bactericidal activity was influenced by the in vitro susceptibility of the offending pathogen and by the presence of in vitro synergism between the given antibiotics. These two variables showed a correlation with the clinical outcome that proved to be increasing with the degree of granulocytopenia. Furthermore, synergistic combination of the antibiotics appeared essential when the in vitro susceptibility shown by the offending pathogen was moderate. These data suggest (i) that determination of the bactericidal activity of the serum may prove to be a useful method to predict the clinical outcome in severely granulocytopenic patients with Gram-negative septicemia; and (ii) under the same conditions, antibiotic combinations that have demonstrable in vitro synergy against the offending pathogen should be given the utmost consideration.

Ceftazidime in neonatal infections

Ninety one neonates received 108 courses of intravenous ceftazidime (25 mg/kg, 12 hourly) over a study period of 15 months. Fourteen had clinically and bacteriologically proved infections. Only one of these had resistant organisms. Four (two with group B beta haemolytic streptococcal infections, one with Escherichia coli meningitis, and one with Staphylococcal aureus septicaemia) failed to respond despite adequate treatment. Bacteriological eradication or clinical improvement, or both, were obtained in the remaining nine. Routine biochemical and haematological values were monitored and there were no side effects. High serum ceftazidime concentrations, well exceeding the minimum inhibitory concentration for most common neonatal pathogens were obtained and maintained throughout treatment. Penetration into the cerebrospinal fluid was excellent in eight of the nine cases studied. Ceftazidime has a theoretical role as a broad spectrum antibiotic suitable for neonatal use with no evident side effects. In this study, however, it was only appropriate for Gram negative infections, and was ineffective against Gram positive organisms. Ceftazidime cannot therefore be recommended as monotherapy before the results of bacteriological culture are known.

Pharmacokinetics of ceftazidime, alone or in combination with piperacillin or tobramycin, in the sera of cancer patients

We administered 2 g of ceftazidime intravenously every 8 h to cancer patients for the empiric therapy of febrile episodes. Ceftazidime was administered as monotherapy for patients with granulocyte counts in excess of 1,000/microliter. Febrile, neutropenic patients were randomized to also receive either piperacillin or tobramycin. The pharmacokinetic profile of ceftazidime during a steady-state dosing interval was ascertained in 21 patients. No differences were seen between groups for any of the pharmacokinetic parameters examined. As expected, the observed half-life was longer, the serum clearance was smaller, and the volumes of distribution were larger than in previously reported studies of volunteers. Serum concentrations remained above the MIC for inhibition of 90% of strains of the most common bacteremic pathogens seen in our cancer center for the entire 8-h dosing interval.

Ceftazidime. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Ceftazidime is a new 'third generation' cephalosporin administered intravenously or intramuscularly. Similarly to other third generation cephalosporins it has a broad spectrum of in vitro activity against Gram-positive and Gram-negative aerobic bacteria, is particularly active against Enterobacteriaceae (including beta-lactamase-positive strains) and is resistant to hydrolysis by most beta-lactamases. Importantly, in vitro ceftazidime is presently the most active cephalosporin available against Pseudomonas aeruginosa, but it is less active against Staphylococcus aureus than first and second generation cephalosporins. Only larger comparative trials are likely to discern any statistically significant differences in clinical efficacy which may exist between ceftazidime and other antibiotics, but ceftazidime appears to be similar in efficacy to 'standard' comparative drugs in lower respiratory tract infections and complicated and/or chronic urinary tract infections among debilitated or hospitalised patients. Thus, in patients having Gram-negative infections at these sites and in whom the potential toxicity of the aminoglycosides is a concern, ceftazidime may be a valuable alternative in that it apparently lacks serious side effects and does not require routine drug plasma concentration monitoring. In fibrocystic patients having acute respiratory tract infections, ceftazidime is highly effective at both reducing symptoms of infection and temporarily reducing the sputum counts of Pseudomonas species. However, in these patients resistance to ceftazidime may develop, as seen with other beta-lactam antibiotics. In the treatment of fever of unknown origin or documented infections in immunocompromised adults and children, ceftazidime appears to be similar in efficacy to various 2- or 3-drug combinations. Nevertheless, the coadministration of an antibiotic having greater efficacy against Gram-positive bacteria should be considered in immunocompromised patients. Results from a small number of comparative trials suggest that ceftazidime may be as effective as the aminoglycosides in intra-abdominal, obstetric and gynaecological, and skin and soft tissue infections. However, further clinical experience, particularly a few well designed comparative studies, is needed to clarify the comparative efficacy in these conditions as well as in septicaemia/bacteraemia, meningitis, and bone and joint infections.

Amikacin + ceftazidime therapy of experimental right-sided Pseudomonas aeruginosa endocarditis in rabbits

We investigated the efficacy of a potent new antipseudomonal beta-lactam agent, ceftazidime, in a model of right-sided Pseudomonas endocarditis in 72 rabbits. Animals received either: no therapy (controls), amikacin (15 mg/kg/day), ceftazidime (100 mg/kg/day) or amikacin + ceftazidime. Amikacin + ceftazidime was significantly more effective than single-drug regimens in terms of reduction of mortality (p less than 0.01), prevention of pulmonary infarction (p less than 0.05), reduction of mean vegetation titers of Pseudomonas aeruginosa (p less than 0.05-p less than 0.0005), sterilization of vegetations (p less than 0.0005) and reduction in prevalence of bacteriologic relapses after therapy (p less than 0.005). There was no development of resistance in vivo to either amikacin or ceftazidime.

Sequential ventricular fluid concentrations of ceftazidime--report of three cases

Three adult subjects, each with a ventriculostomy, received ceftazidime 2g iv q8h for three doses. Serial samples of serum and CSF ventricular fluid were obtained following the third dose; ceftazidime concentrations were measured by high pressure liquid chromatography. In one patient without inflammatory cells in the CSF, ceftazidime CSF concentrations were only approximately 0.3 micrograms/ml. In two other patients who had inflammatory cells and blood in the CSF, concentrations of ceftazidime in ventricular fluid demonstrated a slow rise and decline over an eight-hour period. Although contamination of the CSF by blood in these two patients confounds the interpretation of the concentrations achieved, it is concluded that obtaining serial samples of CSF from a ventriculostomy offers a more realistic appraisal of the dynamics of antibiotic penetration compared with the single-point method.

Serum and sputum concentrations of azlocillin, cefoperazone and ceftazidime in patients with cystic fibrosis

Single-dose pharmacokinetics of azlocillin, cefoperazone and ceftazidime were studied in 17 patients with cystic fibrosis (CF). All patients had broncho-pulmonary infections caused by Pseudomonas aeruginosa. Three groups of five, six, and six patients were treated with azlocillin, cefoperazone, or ceftazidime, respectively. The size of the single dose was 133 mg/kg for azlocillin, 66.7 mg/kg for ceftazidime and 66.7 mg/kg for cefoperazone. The clearance values for the three antibiotics calculated from the single-dose data were, on the average, higher than the values previously reported for normal subjects. After the first dose, the patients received a repeated-dose treatment with the same antibiotic. During the first 5 days of therapy, a complement postural drainage of sputum was obtained four times a day for each patient. Cefoperazone could be measured in 47 (39.2%) of the 120 sputum samples assayed while ceftazidime was shown to be present in all 120 sputum samples examined. Azlocillin was not detected in any of the 100 sputum samples assayed.

Serum and sputum concentrations of ceftazidime in patients with cystic fibrosis

The pharmacokinetic parameters of ceftazidime were assessed in six cystic fibrotic patients during eight courses administered for acute exacerbations of pulmonary infection. In order to assess the initial and steady state concentrations of ceftazidime at a dose of 35 mg/kg and to determine the levels found after a higher dose, each ten day course of ceftazidime consisted of eight doses of 35 mg/kg followed by 22 doses of 50 mg/kg, all administered at 8-hourly intervals. Samples of blood and sputum were collected following the 1st, 8th and 9th doses for ceftazidime assay. The mean peak serum concentrations of ceftazidime were 97, 110 and 147 mg/l respectively with corresponding mean concentrations in sputum of 2.7, 2.6 and 1.6 mg/l. The mean clearance rate was calculated on a two compartment model to be 197 ml/min/50 kg lean body mass, the mean volume of distribution was 281/50 kg lean body mass and the mean half life was 1.57 h. There were large inter-patient differences in the pharmacokinetic parameters, however, which suggests that the clinical condition of the patient affects the pharmacokinetics of ceftazidime in cystic fibrosis. In all the patients, even after the doses of 50 mg/kg, the trough serum concentrations were low. Samples of blood were also collected for adverse effects before, during and after each course; there was no evidence of renal, hepatic or haematological changes in response to the drug.

In vitro evaluation of ceftazidime (GR 20263), amikacin and sisomicin, in a model simulating serum pharmacokinetics of therapeutic doses

The activity of ceftazidime, amikacin and sisomicin was investigated in an in vitro model using varying concentrations of antibiotic which mimic the serum levels of patients after the intramuscular administration of a 500, 250 and 70 mg dose respectively. Using this test, during the time of the agar MIC value correlation, ceftazidime, amikacin and sisomicin proved to be active against strains sensitive to 16 micrograms/ml, 8 micrograms/ml and 4 micrograms/ml respectively. Using the above concentrations as the cut-off points in defining the sensitivity of the strains, ceftazidime revealed the same level of activity as amikacin (6 and 5 resistant strains respectively out of the 185 tested) and proved much more active than sisomicin (48 resistant strains).

Comparison of ceftazidime, cefuroxime and methicillin in the treatment of Staphylococcus aureus endocarditis in rabbits

Ceftazidime, cefuroxime and methicillin proved equally effective in the therapy of experimental Staphylococcus aureus endocarditis in rabbits with a dosing regimen of 40 mg/kg intramuscularly at 8-hourly intervals for three days. Treated animals all demonstrated a thousand to 10,000-fold reduction in the levels of bacteria in the vegetations compared with untreated controls. In-vitro sensitivities of the organism to the test antibiotics were not predictive of therapeutic efficacy in vivo.

Bactericidal activity of ceftazidime in serum compared with that of ticarcillin combined with amikacin

We compared the bactericidal activity of serum attained 1 and 6 h after the termination of infusions of either ceftazidime (2 g) or ticarcillin plus amikacin (5 g and 7.5 mg/kg, respectively) in 6 volunteers against a panel of the most common pathogens found in the blood of febrile granulocytopenic cancer patients. Ceftazidime consistently produced significantly higher serum bactericidal titers at both 1 and 6 h against all species of gram-negative bacilli. Its performance against Pseudomonas aeruginosa was especially impressive. The geometric mean titer against this organism was 1:41 at 1 h, contrasted with 1:12 for ticarcillin plus amikacin (P = 0.025). However, for Staphylococcus aureus, the geometric mean serum bactericidal titer of ceftazidime was 1:3.6 at 1 h and undetectable at 6 h. Ceftazidime shows promise as single-agent therapy for serious gram-negative bacillary infections. Whether this promise is fulfilled and whether the observed antistaphylococcal activity is adequate for empiric therapy in infected granulocytopenic patients need further investigation.

Ceftazidime in the treatment of infective complications of spinal cord lesions

The use and the abuse of the antibiotics are certainly a subject of great concern, particularly for the increasing incidence of multiresistant bacteria. Since these resistant organisms may be sensitive to cephalosporin, we have tested the effectiveness of a new cephalosporin, ceftazidime, in the treatment of resistant infection in spinal cord injured patients. A randomized study of ceftazidime versus amikacin was carried out on twenty patients. The preliminary results are presented.

Pharmacokinetics of ceftazidime in elderly patients and young volunteers

When given 2 g ceftazidime intravenously a group of 13 acutely ill but renally healthy, elderly patients demonstrated prolonged terminal half-life, increased area under the curve and reduced total and renal clearance compared to 9 young, healthy, male volunteers. The volume of distribution was enlarged in elderly males. Ceftazidime elimination correlated to renal function. Dosage twice daily for one week did not result in any clinically significant accumulation.

Pharmacokinetic studies of ceftazidime in serum, bone, bile, tissue fluid and peritoneal fluid

After a single iv bolus injection of 2 g ceftazidime, concentrations were measured in serum and urine in volunteers and in serum, bone, bile and tissue fluid in patients. The serum half-life was 171 min in volunteers (n=6, average age 26 years) and 221 min in patients (n=12, average age 58 years). The peripheral volumes of distribution were also different, being 7.81 in volunteers and 11.31 in patients. Urinary recovery from the volunteers averaged 92% of the dose. Bone samples free from blood and taken from the femoral head, the pelvis or the femoral shaft contained an average of 24.1 mg ceftazidime per litre of organic bone at 30 min after injection and 19.7 mg/l at 2 h. Samples of fluid from the periprosthetic space after hip replacement contained 25.6 mg/l at 2 h and were above 8 mg/l at 10 h. Bile concentrations reached 36.4 mg/l at 90 min and were above 8 mg/l for over 8 h. Peritoneal fluid samples contained 27.6 mg/l at 1 h and 8.0 mg/l at 8 h. These concentrations are considered sufficient to treat most aerobic infections associated with surgery.