Following IM administration of a single 500 mg or 1 g dose of CLAFORAN to normal volunteers, mean peak serum concentrations of 11.7 and 20.5 mcg/mL respectively were attained within 30 minutes and declined with an elimination half-life of approximately 1 hour. There was a dose-dependent increase in serum levels after the IV administration of 500 mg, 1 g, and 2 g of CLAFORAN (38.9, 101.7, and 214.4 mcg/mL respectively) without alteration in the elimination half-life. There is no evidence of accumulation following repetitive IV infusion of 1 g doses every 6 hours for 14 days as there are no alterations of serum or renal clearance. About 60% of the administered dose was recovered from urine during the first 6 hours following the start of the infusion.
Approximately 20–36% of an intravenously administered dose of 14C-cefotaxime is excreted by the kidney as unchanged cefotaxime and 15–25% as the desacetyl derivative, the major metabolite. The desacetyl metabolite has been shown to contribute to the bactericidal activity. Two other urinary metabolites (M2 and M3) account for about 20–25%. They lack bactericidal activity.
A single 50 mg/kg dose of CLAFORAN was administered as an intravenous infusion over a 10- to 15-minute period to 29 newborn infants grouped according to birth weight and age. The mean half-life of cefotaxime in infants with lower birth weights (≤1500 grams), regardless of age, was longer (4.6 hours) than the mean half-life (3.4 hours) in infants whose birth weight was greater than 1500 grams. Mean serum clearance was also smaller in the lower birth weight infants. Although the differences in mean half-life values are statistically significant for weight, they are not clinically important. Therefore, dosage should be based solely on age. (See DOSAGE AND ADMINISTRATION section.)
Drug Interactions
A single intravenous dose and oral dose of probenecid (500 mg each) followed by two oral doses of probenecid 500 mg at approximately hourly intervals administered to three healthy male subjects receiving a continuous infusion of cefotaxime increased the steady-state plasma concentration of cefotaxime by approximately 80%. In another study, administration of oral probenecid 500 mg every 6 hours to six healthy male subjects with cefotaxime 1 gram infused over 5 minutes decreased the total clearance of cefotaxime by approximately 50%.
Additionally, no disulfiram-like reactions were reported in a study conducted in 22 healthy volunteers administered CLAFORAN and ethanol.
Microbiology
Mechanism of Action
Cefotaxime sodium is a bactericidal agent that acts by inhibition of bacterial cell wall synthesis. Cefotaxime has activity in the presence of some beta-lactamases, both penicillinases and cephalosporinases, of Gram-negative and Gram-positive bacteria.
Mechanism of Resistance
Resistance to cefotaxime is primarily through hydrolysis by beta-lactamase, alteration of penicillin-binding proteins (PBPs), and decreased permeability.
Susceptibility to cefotaxime will vary geographically and may change over time; local susceptibility data should be consulted, if available. Cefotaxime has been shown to be active against most isolates of the following bacteria both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section:
Gram-positive bacteria
Enterococcus spp.1
Staphylococcus aureus (methicillin-susceptible isolates only)
Staphylococcus epidermidis
Streptococcus pneumoniae
Streptococcus pyogenes (Group A beta-hemolytic streptococci)
Streptococcus spp. (Viridans group streptococci)
Gram-negative bacteria
Acinetobacter spp.
Citrobacter spp.2
Enterobacter spp.2
Escherichia coli 2
Haemophilus influenzae
Haemophilus parainfluenzae
Klebsiella spp. (including Klebsiella pneumoniae)2
Morganella morganii2
Neisseria gonorrhoeae (including beta-lactamase-positive and negative strains)
Neisseria meningitidis
Proteus mirabilis2
Proteus vulgaris2
Providencia rettgeri2
Providencia stuartii2
Serratia marcescens2
Anaerobic bacteria
Bacteroides spp., including some isolates of Bacteroides fragilis
Clostridium spp. (most isolates of Clostridium difficile are resistant)
Fusobacterium spp. (including Fusobacterium nucleatum)
Peptococcus spp.
Peptostreptococcus spp.
The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following microorganisms exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to 1 mcg/mL. However, the efficacy of cefotaxime in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials.
Gram-negative bacteria
Providencia spp.
Salmonella spp. (including Salmonella typhi)
Shigella spp.
Susceptibility Test Methods
When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drug products used in resident hospitals to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antibacterial drug product for treatment.
Dilution techniques
Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method (broth or agar) 1,2. The MIC values should be interpreted according to the criteria provided in Table 1.
Diffusion techniques
Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized test method2,3. This procedure uses paper disks impregnated with 30 mcg cefotaxime to test the susceptibility of microorganisms to cefotaxime. The disk diffusion interpretive criteria are provided in Table 1.
