[Research and development of new oral cephems, cefixime and cefdinir]

A conventional HPLC-MS method for the simultaneous determination of ofloxacin and cefixime in plasma: Development and validation

OBJECTIVE

A simple, rapid, and sensitive high performance liquid chromatography-mass spectrometry (HPLC-MS) method was developed and validated for the simultaneous determination of ofloxacin (OFL) and cefixime (CEF) in human plasma using the moxifloxacin as internal standard.

METHODOLOGY

Analytes were separated using an Agilent LCMS system equipped with a Zorbax eclipse XBD C18 column (150 mm × 4.6 mm i.d., 5 μm) and using a mobile phase consisting of a mixture of acetonitrile, methanol and 0.5% formic acid in a ratio of 23:10:67% v/v and flow rate was set at 0.6 mL/min. Plasma samples were extracted using the protein precipitation with acetonitrile and analyzed by positive ion mode.

RESULTS

The linearity of the proposed method was investigated in the concentration range of 4-500 ng/mL (r = 0.9996) for OFL and 40-6000 ng/mL (r = 0.9998) for CEF. The lower limits of quantification were 4 ng/mL and 40 ng/mL for OFL and CEF respectively, which reach the level of both drugs possibly found in human plasma. Further, the reported method was validated as per the ICH guidelines and found to be well within the acceptable range.

CONCLUSION

The proposed method is simple, rapid, accurate, precise, and appropriate for pharmacokinetic and therapeutic drug monitoring in the clinical laboratories.

Molecular structure, vibrational spectroscopic, first order hyperpolarizability and HOMO-LUMO studies of 7-amino-8-oxo-3-vinyl-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

The FT-IR and FT-Raman spectra of 7-amino-8-oxo-3-vinyl-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid (7AVCA) were recorded in the region 4000-400 cm(-1) and 3500-10 cm(-1), respectively. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers were carried out by ab initio HF and density functional theoretical methods invoking 6-311G(d,p) basis set. The differences between the observed and scaled wavenumber values of most of the fundamentals are very small. The electric dipole moment (μ) and the first order hyperpolarizability (β0) values have been computed quantum mechanically. The calculated results show that 7AVCA may have microscopic nonlinear optical (NLO) behavior with non-zero values. A detailed interpretation of the FT-IR and FT-Raman spectra of 7AVCA is reported. The theoretical IR and Raman spectra of 7AVCA have also been constructed. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule.

Effect of cefixime and cefdinir, oral cephalosporins, on cytochrome P450 activities in human hepatic microsomes

The effects of two kinds of oral cephalosporins, cefixime and cefdinir, on cytochrome P450 (CYP) activities in human hepatic microsomes were investigated. Both cefixime and cefdinir at 2 mM concentration neither inhibited nor stimulated CYP1A1/2-mediated 7-ethoxyresorufin O-deethylation, CYP2A6-mediated coumarin 7-hydroxylation, CYP2B6-mediated 7-benzyloxyresorufin O-debenzylation, CYP2C8/9-mediated tolbutamide methylhydroxylation, CYP2C19-mediated S-mephenytoin 4'-hydroxylation, CYP2D6-mediated bufuralol 1'-hydroxylation, CYP2E1-mediated chlorzoxazone 6-hydroxylation, CYP3A4-mediated nifedipine oxidation, or CYP3A4-mediated testosterone 6beta-hydroxylation. The free fractions of cefixime and cefdinir in the incubation mixture, which were measured by ultracentrifugation, were 86.1-93.8% and 94.1-97.8%, respectively. These results suggest that both cefixime and cefdinir would not cause clinically significant interactions with other drugs, which are metabolized by CYPs, via the inhibition of metabolism.

Orally active cephalosporins. Part 4: synthesis, structure--activity relationships and oral absorption of novel 3-(4-pyrazolylmethylthio)cephalosporins with various C-7 side chains

A series of 3-(4-pyrazolylmethylthio)cephalosporins with various C-7 side chains was designed, synthesized and evaluated for antibacterial activity and oral absorption in rats. Antibacterial activity against Haemophilus influenzae was markedly increased by the C-7 oxime moiety. Deamination at the 2 position of, or introduction of a substituent such as halogen or methyl to, the 5 position of the (Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino) moiety improved oral absorption. Among these compounds, FR192752 having a (Z)-2-(2-amino-5-chlorothiazol-4-yl)-2-hydroxyiminoacetamido moiety, showed potent antibacterial activity against both Gram-positive and Gram-negative bacteria including H.influenzae and penicillin G-resistant Streptococcus pneumoniae (PRSP). Further, it showed higher oral absorption than CFDN and FK041.

Degradation kinetics and isomerization of cefdinir, a new oral cephalosporin, in aqueous solution. 1

Hydrolytic degradation products of cefdinir were studied in acidic (pH 1), neutral (pH 6), and basic (pH 9) solutions. Seven major degradation products were isolated by preparative and/or high-performance liquid chromatography and characterized by UV, IR, 1H-NMR, and mass spectra. To clarify degradation pathways in each pH solution, kinetic and product analyses during hydrolysis of cefdinir were carried out along with the followup reaction of representative degradation products. Cefdinir was shown to degrade via two major degradation routes: beta-lactam ring-opening and pH-dependent isomerizations (lactonization, epimerization at C-6 or C-7, syn-anti isomerization of N-oxime function).