Yet Another Doctor Blog On The Internet

Development of an HPLC assay to study the effect of endogenous and exogenous substances on heat-induced aggregation of human serum albumin.


The in vitro activity of FK041, a new orally active cephem antibiotic, against a wide variety of clinical isolates of bacteria was investigated and compared with those of cefdinir (CFDN) and cefditoren (CDTR). FK041 exhibited broad spectrum activity against reference strains of Gram-positive and Gram-negative aerobes and anaerobes. FK041 was active against clinical isolates of Gram-positive organisms except Enterococcus faecalis with MIC90s less than 1.56 microg/ml. FK041 was more active than CFDN and CDTR against Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus agalactiae and was comparable to CFDN and CDTR against Streptococcus pyogenes and Streptococcus pneumoniae. FK041 had no activity against methicillin-resistant staphylococci, like CFDN and CDTR. FK041 showed moderate activity against penicillin-resistant S. pneumoniae with an MIC range of 0.05 approximately 3.13 microg/ml, and was superior to CFDN but inferior to CDTR. Against clinical isolates of many Gram-negative organisms such as Neisseria gonorrhoeae, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, FK041 had good activity comparable or superior to those of CFDN and CDTR. However, it was inferior to CDTR in activity against Moraxella catarrhalis, Haemophilus influenzae, Morganella morganii, and Serratia marcescens, and was inactive against Pseudomonas aeruginosa. With FK041 a small difference between MIC and MBC against S. aureus, E. coli, K. pneumoniae, and H. influenzae was found, indicating that its action is bactericidal against these species. FK041 was stable to group 2beta-lactamase hydrolysis but was unstable to group 1beta-lactamase hydrolysis. The stability of FK041 to these enzymes was similar to those of CFDN and CDTR. FK041 showed high affinity for the main penicillin-binding proteins (PBPs) of S. aureus (PBP 3, 2, and 1) and E. coli (PBP 3, 4, lbs, 2, and 1a).

We evaluated in vitro and in vivo activities of cefpodoxime proxetil (CPDX-PR) in comparison with other oral beta-lactams, cefdinir (CFDN), cefditoren pivoxil (CDTR-PI), and faropenem (FRPM), against penicillin-susceptible and -resistant Streptococcus pneumoniae. In vitro activities (MICs) of CPDX, CFDN, CDTR, and FRPM against clinical isolates, penicillin-susceptible S. pneumoniae (PSSP: MIC of penicillin G, < or = 0.063 microgram/ml), penicillin-intermediate S. pneumoniae (PISP: MIC of penicillin G, 0.125-1 microgram/ml), and penicillin-resistant S. pneumoniae (PRSP: MIC of penicillin G, > or = 2 micrograms/ml), were tested by an agar dilution method. The MIC80s of CPDX against 27 PSSP strains, 23 PISP strains, and 23 PRSP strains were 0.032, 1, and 8 micrograms/ml, respectively, which were superior to or equal to those of CFDN (0.063, 4, and 8 micrograms/ml) and were inferior to those of CDTR (0.016, 0.5, and 1 microgram/ml) and FRPM (< or = 0.008, 0.25, and 1 microgram/ml). Infection was induced in mice by inoculating with a PRSP clinical isolate, 9605 or 9601 (serotype 6), or 10692 (serotype 19), through the nares of male ddY mice into the lungs. The mice were treated with drugs with doses of 2-50 mg/kg at 18, 26, 42, and 50 hours after the infection. Viable cell numbers in the lungs and blood were assayed at 66 hours after the infection. The efficacy of each drug was dose-dependent. CPDX-PR showed the most potent in vivo efficacy among the drugs tested against the infections caused by the PRSP strains. MICs of the drugs against PRSP 9605, 9601, and 10692 were as follows: CPDX, 4, 4 and 2 micrograms/ml; CFDN, 16, 16, and 4 micrograms/ml; CDTR, 1, 1, and 0.5 microgram/ml; and FRPM, 1, 0.5, and 0.5 microgram/ml, respectively. Thus, CPDX-PR showed a stronger in vivo activity than that expected from the MICs of CPDX. This was probably caused by the pharmacokinetic advantage of CPDX over the other drugs used in this study.

We performed pharmacokinetic analyses on 37 infants and children who were given cefdinir in dosages of 14 or 25 mg/kg once daily for 10 days, for the treatment of respiratory and skin or skin structure infections. Cefdinir plasma concentrations were determined with validated liquid chromatology, and pharmacokinetics and pharmacodynamics were determined in relation to the minimum inhibitory concentration values of S. pneumoniae.

A simple, fast, specific, stability-indicating, and precise reversed-phase liquid chromatographic method was developed for the determination of Cefdinir in its different dosage forms, i.e., capsules and suspensions. The method was developed and optimized by analyzing the placebo preparation, formulations, and degraded samples of the drug substance according to the International Conference on Harmonization. The proposed method can successfully separate the drug from degradation products formed under stress conditions along with pharmaceutical ingredients such as preservatives. The developed method was used successfully to determine Cefdinir in capsules and Insta-use suspensions. The developed method was found to be linear for a concentration range of 6-14 microg/mL. Average recoveries obtained with the method were 99.3 +/- 0.4 and 99.6 +/- 0.4% for Insta-use suspensions and capsules, respectively. The method was shown to be specific, precise, and robust.