Pharmacokinetics of cefmetazole in normal subjects and in patients with impaired renal function

Pharmacokinetics/pharmacodynamics analysis and establishment of optimal dosing regimens using unbound cefmetazole concentration for patients infected with Extended-Spectrum β-lactamase producing Enterobacterales (ESBL-E)

STUDY OBJECTIVE

Establish methods for measuring cefmetazole (CMZ) concentrations conduct a pharmacokinetic/pharmacodynamic (PK/PD) analysis using unbound CMZ concentrations for extended-spectrum β-lactamase producing enterobacterales (ESBL-E) and investigate optimal dosing regimens for not undergoing hemodialysis (non-HD) and undergoing hemodialysis (HD) patients.

DESIGN

Prospective observational study.

PATIENTS

Included patients treated with CMZ who provided written informed consent and were admitted to the Tokyo Bay Urayasu Ichikawa Medical Center between August 2021 and July 2022.

MEASUREMENTS

Total and Unbound CMZ concentration was measured by high-performance liquid chromatography (HPLC) with solid-phase extraction and ultrafiltration.

SETTING

Determining the CMZ dosing regimen involved modified creatinine clearance (CLCR ) with measured body weight (BW) using the Cockcroft-Gault equation. For non-HD patients, blood samples were collected during at least three points. For patients undergoing HD, 1 g was administered via intravenous infusion, or rapid intravenous injection after HD, or 30 min before the end of HD. Blood samples were collected before HD (pre-HD), and 1 and 3 h after starting HD and post-HD. All blood samples were collected at steady-state. Patient information was collected from electronic medical records. An unbound PK model was constructed for the non-HD patients. A nomogram was constructed using Monte Carlo simulations with a 90% probability of target attainment at 70% free time above the minimum inhibitory concentration (MIC). For the HD patients, a nomogram was used to determine the optimal dosing regimen for each HD schedule.

MAIN RESULTS

CMZ measurement methods were established. A model analysis of unbound PK in 37 non-HD patients incorporated creatinine clearance (CLCR ) using the Cockcroft-Gault equation, albumin (ALB) for clearance and body weight (BW) for the volume of distribution. In Monte Carlo simulations, nomograms corresponding to the MIC (known and unknown) were generated for each covariate. Using the nomogram, non-HD patients with an ESBL-E MIC of 8 mg/L, a BW of 60 kg, an ALB of 25 g/L, and a CLCR of 60 mL/min required administration of 2 g every 6 h (1- and 3-h infusions). Unbound PK model parameters were calculated for 7 HD patients, and the optimal dosing regimens following PK/PD were determined for each HD schedule. In HD patients, the regimen after and during HD was established using a treatment that was effective up to an ESBL-E MIC of 4 mg/L.

CONCLUSIONS

The nomogram for CMZ regimens established by PK/PD analysis of measured CMZ concentrations enables optimal CMZ dosing for ESBL-E-infected patients.

Pharmacokinetic-pharmacodynamic analysis of cefmetazole against extended-spectrum β-lactamase-producing Enterobacteriaceae in dogs using Monte Carlo Simulation

Introduction

The spread of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) is a serious concern in companion animal medicine owing to their ability to develop multidrug resistance. Cefmetazole (CMZ) is a candidate drug for treating ESBL-E infections; however, its regimen in dogs has not been established. In this study, we investigated the pharmacokinetic (PK) indices of CMZ in dogs and performed PK-pharmacodynamic (PD) analyses using Monte Carlo Simulation (MCS).

Methods

In total, six healthy dogs received an intravenous bolus dose of CMZ (40 mg/kg body weight). Serum CMZ concentrations were evaluated using liquid chromatography-mass spectrometry, and PK indices were determined based on non-compartmental analysis. The PK-PD cut-off (COPD) values were calculated as the highest minimum inhibitory concentration (MIC) that achieved ≥90% probability of target attainment for a target value of unbounded drug concentration exceeding 40% of the dosing interval. The cumulative fraction of response (CFR) was calculated based on the MIC distribution of wild-type ESBL-E from companion animals.

Results

The area under the concentration-time curve and elimination half-time were 103.36 ± 7.49 mg·h/L and 0.84 ± 0.07 h, respectively. MCS analysis revealed that COPD values for regimens of 40 mg/kg q12, q8h, and q6h were ≤ 0.5, ≤2, and ≤ 4 μg/mL, respectively. A regimen of 40 mg/kg q6h was estimated to achieve a CFR of 80-90% for Escherichia coli and Klebsiella pneumoniae. By contrast, all regimens exhibited a CFR of ≤70% for Proteus mirabilis and Enterobacter cloacae.

Discussion

We conclude that CMZ at 40 mg/kg q6h could be a viable treatment regimen for dogs infected with ESBL-producing Escherichia coli and Klebsiella pneumoniae.

In vitro efficacy of humanized regimen of flomoxef against extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae

This study compared the efficacy of flomoxef with other β-lactam antibiotics against extended-spectrum β-lactamases (ESBL)-producing bacteria of clinical relevance. First, the prevalence and β-lactamase genotypes of ESBL-producing strains among Escherichia coli and Klebsiella pneumoniae isolates collected in Japan from 2004 to 2018 were investigated. High MIC90 values (>64 µg/mL) of ceftriaxone, cefepime, and ceftazidime and low MIC90 values (≤0.06-2 µg/mL) of flomoxef, cefmetazole, and meropenem against both species were observed. Second, a chemostat model was used to analyze the efficacy of humanized regimens of three oxacephem/cephamycin antibiotics (flomoxef, cefmetazole, cefoxitin) and two other antibiotics (meropenem and piperacillin/tazobactam) in suppressing the growth of five ESBL-producing E. coli and two K. pneumoniae strains. Flomoxef, piperacillin/tazobactam, and meropenem showed good bactericidal effects with >4 log10 CFU/mL reduction without bacterial regrowth at 24 h even when the MIC of test isolates was >MIC90. Cefmetazole and cefoxitin resulted in regrowth of test isolates with MIC ≥MIC90 at 24 h. Cefmetazole, cefoxitin, flomoxef, and meropenem showed increased MICs for regrown samples. A clear relationship between the proportion of time that the free drug concentration exceeded the MIC (%fT>MIC) and antibiotic efficacy was found for flomoxef, cefoxitin, and cefmetazole, and flomoxef had the highest %fT>MIC, whereas discrepancies between Clinical and Laboratory Standards Institute breakpoint and bactericidal activity were observed for cefmetazole. Flomoxef was effective in preventing the growth of all ESBL-producing strains, even those with an MIC eight times the MIC90. Thus, flomoxef may be a good alternative to meropenem in context of carbapenems sparing stewardship.

Clinical pharmacokinetics of antibiotics in patients with impaired renal function

Many antibiotics are eliminated renally and dosage adjustments are commonly made in patients with renal insufficiency. This is a critical review of antibiotic pharmacokinetics in patients with various degrees of renal function. Detailed information regarding pharmacokinetic alterations with specific antibiotics or antibiotic classes has been compiled and tabulated. From pharmacokinetic evidence, recommendations for dosage adjustments of antibiotics are supplied. The criteria used for assigning rating levels to specific pharmacokinetic articles as well as the grading system for dosage adjustments are outlined. In addition, a basic review of pharmacokinetic alterations in renal failure and factors affecting the removal of drugs by haemodialysis is included.

Pharmacokinetics and dose proportionality of cefmetazole in healthy young and elderly volunteers

The pharmacokinetics and dose proportionality of cefmetazole were studied in 24 healthy volunteers (12 young and 12 elderly). Each volunteer received single 0.5-, 1-, and 2-g doses of cefmetazole administered intravenously over 5 min according to a three-way crossover design. Serial plasma and urine samples were collected over a 24-h period following dosing and assayed for cefmetazole by a high-performance liquid chromatography method. Results of the dose proportionality portion of the study indicated that cefmetazole pharmacokinetics are linear and proportional with dose in both age groups. Comparisons of pharmacokinetic parameters between the young and elderly groups indicated that the systemic clearance was significantly lower in elderly than in young volunteers (92.4 versus 112 ml/min). Additionally, creatinine clearance was significantly lower in elderly (74.1 ml/min) than in young (92.9 ml/min) subjects. No significant differences between age groups were observed for volume of distribution, urinary recovery, terminal half-life, nonrenal clearance, or renal clearance, although half-life was slightly prolonged in elderly volunteers relative to that in young volunteers (1.54 versus 1.34 h), and renal clearance was slightly lower in elderly than in young volunteers (83.7 versus 96.1 ml/min). Both systemic and renal clearance were significantly correlated with creatinine clearance. These results indicate that the observed age-related differences in the pharmacokinetics of cefmetazole are most likely due to differences in renal function between the two age groups. The small reduction in cefmetazole elimination in the elderly would not warrant dose adjustment in this population.

Disposition of cefmetazole in healthy volunteers and patients with impaired renal function

The disposition of cefmetazole was studied in 25 subjects with various degrees of renal function after a 1,000-mg, constant-rate, 30-min intravenous infusion of cefmetazole sodium. In six subjects with creatinine clearance (CLCR) of greater than 90 ml/min per 1.73 m2 (group 1), the terminal elimination half-life (t1/2 beta) was 1.31 +/- 0.54 h (mean +/- standard deviation), cefmetazole total body clearance (CLP) was 132.8 +/- 25.1 ml/min per 1.73 m2, and volume of distribution at steady state was 0.165 +/- 0.025 liter/kg. The fraction of dose excreted unchanged in the urine was 84.0% +/- 26.1%. Subjects with CLCRS of 40 to 69 (group 2, n = 6) and 10 to 39 (group 3, n = 6) ml/min per 1.73 m2 demonstrated prolongation of the t1/2 beta (3.62 +/- 1.06 and 5.93 +/- 1.81 h, respectively) and significant reductions in cefmetazole CLP (52.8 +/- 14.3 and 30.2 +/- 10.2 ml/min per 1.73 m2, respectively), compared with group 1. In seven subjects on chronic hemodialysis (group 4) studied during an interdialytic period, the cefmetazole t1/2 beta was increased to 24.10 +/- 8.12 h and the CLP was reduced to 6.8 +/- 2.1 ml/min per 1.73 m2. Cefmetazole CLP correlated positively with CLCR (r = 0.951, P less than 0.001): CLP = (1.181 . CLCR) -- 0.287. The disposition of cefmetazole was also assessed in six group 4 subjects during an intradialytic period. The t1/2 beta during hemodialysis (2.09 +/- 0.69 h) was significantly shorter than that observed during the interdialytic period. The hemodialysis clearance of cefmetazole was 86.1 +/- 20.1 ml/min, and the fraction of cefmetazole removed during hemodialysis was 59.8% +/- 5.9%. It is recommended that patients with renal insufficiency received standard doses of cefmetazole at extended intervals and patients on maintenance hemodialysis received standard doses after hemodialysis.

Cefmetazole (CS-1170), a "new" cephamycin with a decade of clinical experience

In vitro and in vivo study results were reviewed from cefmetazole, a "new" parenteral cephamycin. Cefmetazole's spectrum of activity was comparable to that of second-generation cephalosporins, which includes clinical coverage of many Enterobacteriaceae, Staphylococcus spp., streptococci, Haemophilus spp., pathogenic Neisseria, Branhamella catarrhalis, and anaerobic bacteria. Cefmetazole was generally more potent (two- to eightfold) than cefoxitin against organisms within their spectrums and was particularly active for staphylococci (MIC90, 2.0 micrograms/ml). Methicillin-resistant S. aureus strains were more susceptible to cefmetazole alone or in combination (fosfomycin) than any other cephamycin. Cefmetazole has demonstrated excellent stability to aerobic and anaerobic organism-produced beta-lactamases. It also inhibits Type I cephalosporinases and, uniquely, some other cephalosporinases produced by the Bacteroides. This superior stability, enzyme interaction, and better penetration into bacterial cells results in a sustained bactericidal effect and a capacity for more infrequent dosing. The cefmetazole serum elimination half-life was 1.5 hr, also justifying use at greater than or equal to 8-hr intervals. Clinical trials in the United States and Japan demonstrated an acceptably high cefmetazole infection cure rate (88% to 100%), especially in direct comparative studies with cefoxitin. Cefmetazole was also proven very effective in minimizing infectious wound morbidity (prophylaxis) using 2 g single- or multidose regimens. Adverse drug reactions were usually minor; in the Japanese surveillance trial (118,318 patients) the rate was only 2.2% (8.8% in United States). Cefmetazole has been extensively and safely used in Japan since 1980.

Pharmacokinetics of intravenous cefmetazole with emphasis on comparison between predicted theoretical levels in tissue and actual skin window fluid levels

Cefmetazole is a cephamycin antibiotic which is resistant to hydrolysis by various beta-lactamases. This study evaluated the pharmacokinetics of cefmetazole, including its intravascular and interstitial fluid distribution, by using the skin window (SW) technique. A 2-g dose of cefmetazole was given intravenously over 30 min to each of 12 healthy adult male volunteers every 6 h for nine doses. Plasma levels were assayed at predetermined intervals after doses 1, 5, and 9. Interstitial fluid levels were determined by the SW technique. Antibiotic levels were assayed by the agar well bioassay technique. A concentration-versus-time plot indicates that cefmetazole is rapidly distributed, with mean peak levels in plasma equal to 126 micrograms/ml at the end of the half-hour infusion. The mean plasma half-life was 1.1 h. Plasma and tissue distribution constants permitted calculation of theoretical levels in tissue. Parallel elimination slopes for SW and theoretical tissue level showed that the SW model distribution kinetics are closely related. The area under the curve for the SW was 73.9 mg.h/liter. This was comparable to the theoretical level in tissue, which was 96 mg.h/liter. Furthermore, the area under the curve of theoretical tissue level/plasma was 0.6 and that of SW/plasma was 0.47. These results demonstrate that the SW technique yielded a result quite close to the theoretical tissue level. Ultrafiltration analysis indicated that as cefmetazole levels in plasma increased from 10 to 250 micrograms/ml, plasma protein binding of the antibiotic dropped from 85 to 65%. Finally, 60 to 70% of the drug was recovered from the urine as biologically active drug over 6 h postinfusion.

Pharmacokinetics of single-dose cefmetazole following intramuscular administration of cefmetazole sodium to healthy male volunteers

The tolerance and pharmacokinetics of cefmetazole were studied in healthy male volunteers who received a placebo (sterile saline) or a single dose of cefmetazole sodium intramuscularly. Drug-treated volunteers received one of four doses, 0.375, 0.750, 1, or 2 g. The drug was well tolerated, with no adverse medical events or laboratory changes observed during the study that could affect the pharmacokinetic interpretation of the data. Cefmetazole concentrations were determined by using a specific high-performance liquid chromatographic method. Serum cefmetazole concentrations were well described by a one-compartment open model with first-order absorption and elimination. Cefmetazole was rapidly absorbed in most volunteers, with a mean time to maximum concentration in serum of 1.24 +/- 0.12 h (+/- standard error of the mean), and the mean maximum concentration in serum increased from 17.0 +/- 1.6 to 74.2 +/- 9.5 micrograms/ml over the 0.375- to 2-g dose range. Maximum concentrations in serum, areas under serum concentration-time curve, and urinary excretion of intact drug increased in proportion to cefmetazole sodium dose. Times at which maximum concentrations in serum occurred, apparent volumes of distribution, steady-state volumes of distribution, absorption and elimination half-lives, and systemic clearances did not change significantly (P greater than 0.05) with drug dose. Although absorption and elimination half-lives were not significantly different in 10 of 40 volunteers (P greater than 0.05), in a majority of subjects elimination half-lives were approximately 10 times longer than absorption half-lives. The mean recovery of intact drug in urine ranged from 68.8 to 86.0% over the dose range studied, with a mean recovery over all doses of 77.1 +/- 2.4%. Rental clearances were significantly lower (P < 0.05) for the two lowest doses (93.0 and 84.3 versus 115.0 and 118.0 ml/min); these differences are not considered clinically important. The results of this study indicate that cefmetazole pharmacokinetics are linear after administration of single intramuscular doses ranging from 0.375 to 2 g, that clinically relevant concentrations of cefmetazole in serum (1 to 2 micrograms/ml) persist in a majority of volunteers for more than 8 h after administration of 0.750-g or higher doses, and that clinically relevant concentrations of cefmetazole continue to be excreted in urine 8 to 12 h after administration of 0.375- to 2-g doses.

Pharmacokinetics of intravenously administered cefmetazole and cefoxitin and effects of probenecid on cefmetazole elimination

Sixteen healthy male volunteers participated in a randomized, balanced, three-way crossover study comparing the pharmacokinetics of cefmetazole, cefoxitin, and cefmetazole with probenecid pretreatment. Single 2-g doses of cefmetazole sodium and cefoxitin sodium were given intravenously as a 5-min infusion. Concentrations of cefmetazole and cefoxitin were determined by using a specific semiautomated high-performance liquid chromatographic method. Concentration-time profiles of cefmetazole and cefoxitin declined in a biexponential manner from peak levels. Compared with cefoxitin, cefmetazole had a significantly (P less than 0.05) higher mean (+/- standard error of the mean) peak concentration in serum (290 +/- 11 versus 244 +/- 10 micrograms/ml), a longer terminal disposition half-life (1.50 +/- 0.14 versus 0.81 +/- 0.04 h), lower systemic clearance (111.7 +/- 4.7 versus 279 +/- 12 ml/min) and renal clearance (78.7 +/- 4.3 versus 221 +/- 14 ml/min) of intact drug, and a slightly smaller steady-state volume of distribution (10.3 +/- 0.21 versus 12.8 +/- 0.48 liters). Mean recoveries of cefmetazole and cefoxitin in urine were approximately 71 and 77%, respectively. Pretreatment of volunteers with probenecid (1 g orally) significantly (P less than 0.05) increased concentrations of cefmetazole in serum 1 h after drug administration without significantly increasing maximum concentrations in serum. Mean areas under the concentration-time curve (466 +/- 27 versus 295 +/- 13 micrograms.h/ml) and terminal disposition half-lives (2.27 +/- 0.13 versus 1.50 +/- 0.14 h) of cefmetazole increased. Systemic clearance (72.1 +/- 4.0 versus 111.7 +/- 4.7 ml/min) and renal clearance (47.4 +/- 4.0 versus 78.7 +/- 4.3 ml/min) of intact antibiotic decreased. Mean recoveries (65.9 +/- 3.7 versus 71.0 +/- 3.2%) of intact cefmetazole in urine were not significantly (P > 0.05) different. Elimination of cefmetazole in urine was also significantly prolonged by probenecid, with substantial concentrations of cefmetazole (>/= 20 micrograms/ml) found in the 12- to 24-h urine collection for 14 to 16 volunteers. The results show that cefmetazole remains at clinically relevant concentrations (1 to 2 micrograms/ml) approximately twice as long as cefoxitin, that serum cefmetazole can be maintained longer at clinically significant concentrations with preadministration of probenecid, and that cefmetazole is partially eliminated by renal tubule secretion.

Renal disease and drug metabolism: an overview

Renal disease will perturb the disposition of drugs that primarily depend upon renal excretory function for elimination. While changes in drug half-life (T1/2) are often cited as evidence of altered drug disposition, it must be remembered that T1/2 is a dependent variable whose magnitude varies directly with volume of distribution (Vd) and indirectly with total body clearance (ClT). ClT is the one term that succinctly describes drug elimination. ClT is defined as the sum of the renal (ClR) and nonrenal (ClNR), or metabolic, clearances of a drug. Renal failure has been shown to alter the hepatic microsomal mixed-function oxidase system of drug metabolizing enzymes. Therefore, in end-stage renal failure, the potential exists for the modification of the disposition of drugs whose elimination is primarily hepatic. The kidneys themselves contain many of the enzymes important in hepatic drug metabolism. Drugs such as morphine, paracetamol, and p-aminobenzoic acid are metabolized in the kidney and experimental renal disease has been shown to reduce drug metabolism in the diseased kidney compared with the contralateral normal kidney. Renal disease, then, has the potential to alter not only the renal clearance of unchanged drug but also may substantially modify the metabolic transformation of drugs in both the liver and the kidneys. It can no longer be assumed that the pharmacokinetics of drugs that are disposed mainly by metabolism will be unaltered in renal failure.

Pharmacokinetics of cefmetazole administered intramuscularly and intravenously to healthy adults

The pharmacokinetics of cefmetazole, a new parenteral cephalosporin, administered intravenously and intramuscularly at a dose of 30 mg/kg to two groups of seven healthy volunteers were studied. Concentrations in serum were monitored over 8 h by a high-pressure liquid chromatography technique. The plasma concentration-time data were statistically fitted to a biexponential equation for both administration routes, and the data were analyzed by a two- and one-compartment kinetic model, respectively. For the dose range and the administration routes used, the pharmacokinetics of cefmetazole proved to be essentially linear, with clearances from plasma ranging between 3.8 and 12.5 liters/h. The mean maximum concentration in plasma after intramuscular administration of the drug was 90.1 micrograms/ml at 0.7 h. The elimination half-life, about 1.3 h, did not show statistically significant differences for the two routes of administration studied.

Pharmacokinetics of cefotetan in normal subjects and patients with impaired renal function

The elimination kinetics of cefotetan (YM09330), a new parenteral semisynthetic cephamycin derivative, were studied in eight healthy volunteers and 41 patients with renal insufficiency after the administration of a single 500-mg dose intravenously. Concentrations of cefotetan in serum and urine were determined by both bioassay and high-pressure liquid chromatography. The pharmacokinetic parameters for cefotetan were calculated on the basis of a two-compartment open model. Serum concentrations of cefotetan immediately after administration were approximately 180 micrograms/ml in all subjects regardless of function; however, serum concentrations during the beta-phase increased directly with the degree of renal impairment. The mean serum half-life during the beta-phase was 3.0 h in normal subjects as compared with 13.1 h in hemodialysis patients. There was a linear correlation (P less than 0.0001) between the elimination rate constant of cefotetan and creatinine clearance. The mean cumulative urinary recovery of cefotetan in the 24-h urine was 83.3% of the administered dose in normal subjects and decreased with reduced renal function.