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

Isolation and Characterization of An Allergic Dimer Impurity in Cefmenoxime Hydrochloride by NMR and HR-MS Method

Background:

We systematically characterized an allergic dimer impurity in cefmenoxime hydrochloride raw material by UV, IR, HR-MS, 1D and 2D NMR for the first time.

Methods:

The dimer stock solution of cefmenoxime hydrochloride was obtained by degradation method. The target dimer impurity in stock solution was separated by preparative RP-HPLC, and purified by freeze-drying method. The dimer’s functional groups corresponding to the characteristic peaks of UV and IR spectra were analyzed by comparison with cefmenoxime hydrochloride and its molecular formula and mass fragmentation pattern were deduced by HR-MS.

Results:

Then based on the full assignment of 1H and 13C NMR signals，the dimerized position was confirmed and its absolute configuration was identified by 1D and 2D NMR.

Conclusion:

This study provided a structural basis for the allergic study of dimer impurities in cephalosporin drugs.

The antimicrobial activity of cefotaxime: comparative multinational hospital isolate surveys covering 15 years

The "third-generation" cephalosporins (3GC) have emerged as one of the most significant therapeutic entities in the last 15 years. These 3GC compounds (using cefotaxime as a model) have generally maintained their potency and spectrum of activity against important pathogens. However, the continuing popularity of this class associated with local, regional, or national-level use or abuse has led to efficacy reduction against some organism populations associated with selection of Class I cephalosporinase, stably derepressed mutants predominantly among Citrobacter and Enterobacter spp.; emergence of extended-spectrum beta-lactamase producing Enterobacteriaceae (usually Klebsiella spp.), as well as some isolates mimicking Class I-type resistance patterns; and lastly, altered PBP-mediated resistances among pneumococci, Haemophilus influenzae and pathogenic Neisseria spp. Some of these resistance patterns had been present prior to the clinical introduction of 3GCs and have only significantly threatened their use in the last 5 years. Prudent application of these 3GC drugs should be the goal for this decade as follows: 1) use as monotherapy at appropriate doses and frequencies only for organisms with low potential for mutational events; 2) use combination therapy routinely for organisms such as Citrobacter, Enterobacter, some indole-positive protease and Pseudomonas aeruginosa, to minimize emerging resistance clones; 3) use conservatively in high risk patients to minimize "super-colonization" by emerging problem bacteria (e.g. vancomycin-resistant enterococci, Xanthomonas maltophilia etc.); 4) use only those agents among 3GCs that have documented safety, broad clinical applications to all age groups, acceptable pharmacokinetic features and clear cost-saving potential; and 5) use in prophylaxis (surgical procedure, selective decontamination), should be focused toward single-dose or short-course regimens to reduce total hospital-wide exposure to broad-spectrum beta-lactam drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Considerations in dosage selection for third generation cephalosporins

Pharmacokinetic parameters of third generation cephalosporins vary widely, requiring different dosage regimens and adjustment methods for each agent. Although their antibacterial spectrum favours their usage in infections caused by aerobic Gram-negative organisms, due to their limited post-antibiotic effect against these organisms, dosage regimens should ensure that free drug concentrations at the site of infection remain above the minimum inhibitory concentration for as much of the dosage interval as possible in patients with normal host defence mechanisms and for the entire dosage interval in immunocompromised patients. Altered protein binding encountered in various disease states can affect both microbiological and pharmacokinetic properties especially for drugs with high protein binding. Since the concentrations at the site of action are often different from those in serum, a higher or lower range of dosages needs to be selected depending on the target site. Decreased renal function affects the elimination of most third generation cephalosporins, whereas the presence of hepatic disease does not generally necessitate dosage adjustment. Because of the complex age-related physiological changes in paediatric and elderly patients, dosage should be adjusted on the basis of the reported pharmacokinetic data in these populations. The usual recommended dose may or may not be optimal in a given condition depending on the complex interactions between pharmacokinetic, microbiological and other host factors.

Pharmacological properties of cephalosporins

The cephalosporins differ in the substituents attached at the 3 and/or 7 positions of the molecule. Very schematically, substitution at C3 mainly modifies the overall pharmacokinetic properties whereas substitution at position 7 influences the antibacterial characteristics. When using the more common "generation" system for classification, three generations can be distinguished on the basis of their antibacterial spectrum, potency, and their stability to beta-lactamases. The first generation cephalosporins have similar antibacterial and pharmacokinetic characteristics. C3-esterified cephalosporins (e.g. cephalothin and cephapirin) are significantly metabolized. The so-called second generation cephalosporins exhibit only minor differences with respect to the pharmacokinetic properties in contrast to the third generation cephalosporins. The apparent volumes of distribution of most cephalosporins range between seven and 20 1, indicating that they mainly stay in the extracellular space. Plasma protein binding is variable from compound to compound. Generally, the major route of elimination of most cephalosporins is via the kidney except for cefoperazone and ceftriaxone which are both excreted to a large extent by the biliary route. With the exception of cefonicid, cefotetan and cefriaxone, which have longer elimination half-lives (i.e. 4.5, 3.5 and around eight hours), all other cephalosporins have a half-life ranging from 0.5 to 2.5 hours. The pattern of adverse reactions is comparable for all the cephalosporins although there are slight differences in both the incidence and the type of reactions. The major categories of adverse reactions are gastrointestinal, dermatologic, hypersensitivity, haematologic, hepatic, renal as well as CNS effects. Alcohol intolerance (antabus-like effect) can occur when cephalosporins containing the NMTT moiety are administered concomitantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative antimicrobial activity of aminothiazolyl methoxyimino cephalosporins against anaerobic bacteria, including 100 cefoxitin-resistant isolates

Three aminothiazolyl methoxyimino cephalosporins (ceftizoxime, ceftriaxone, and cefotaxime with and without its metabolite) were tested against 500 strains of anaerobic bacteria using the NCCLS reference agar dilution procedure. Eighty-seven percent of all strains tested were from the Bacteroides fragilis group. When tested against a collection of 100 cefoxitin-resistant isolates, ceftizoxime and the cefotaxime/desacetyl-cefotaxime combination were the most active in vitro, inhibiting 32-38% of strains. Ceftriaxone inhibited the greatest number (87%) of cefoxitin-susceptible anaerobes at less than or equal to 32 micrograms/ml. A regional variation in the activity of these drugs was confirmed when an additional 300 isolates were examined from three medical centers. Cefotaxime, ceftizoxime, and ceftriaxone were essentially equal in overall antimicrobial activity, although each drug was judged the best at one of the three locations. Cefoxitin resistance (MIC greater than or equal to 32 micrograms/ml) was consistent among the institutions at a 25% incidence for all organisms tested, and 28% cefoxitin resistance among the B. fragilis group strains. Cefoxitin resistance was not determined to be associated with a beta-lactamase mechanism, but ceftriaxone and other aminothiazolyl cephems were hydrolyzed, thus elevating their MICs. Regional variation in anaerobic organism susceptibility to cephamycins and cephalosporins in company with the variable beta-lactam resistance mechanisms seems to require periodic, epidemiologic monitoring of in vitro drug activity by appropriate methods to assure continued antimicrobial efficacy.