Synthesis and structure-activity relationships of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3' or C-7 catechol or related aromatics

A series of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3' catechol-containing (pyridinium-4-thio)methyl groups and 2-isocephems with C-7 catechol related aromatics have been prepared and evaluated for antimicrobial activity. It turns out that these compounds have highly potent activity against Gram-negative bacteria, especially resistant pathogens such as Pseudomonas aeruginosa. The most active compound of the series was (6S,7S)-7-[2-(2-aminothiazol-4-yl)-2-[(Z)-[(1,5-dihydroxy-4-pyr idon-2-yl) methoxy]imino]acetamido]-3-[[[(4-methyl-5-carboxymethyl)thiazol-2- yl] thio]methyl]-8-oxo-1-aza-4-thiabicyclo [4.2.0] oct-2-ene-2-carboxylic acid which exhibited potent in vitro activity against clinically isolated P, aeruginosa and Acinetobacter baumanii which is also resistant to many anti-infectives, and good in vivo efficacy against clinically isolated P aeruginosa.

Stability of ceftazidime sodium and teicoplanin sodium in a peritoneal dialysis solution

The stability of ceftazidime sodium and teicoplanin sodium separately and in combination in a peritoneal dialysis (PD) solution was studied. PD solutions containing ceftazidime 100 micrograms/mL (as the sodium salt), teicoplanin 25 micrograms/mL (as the sodium salt), or ceftazidime 100 micrograms/mL plus teicoplanin 24 micrograms/mL were prepared in triplicate for each of two conditions: condition A, storage at 25 degrees C (room temperature) for 24 hours, then at 37 degrees C for eight hours; and condition B, storage for seven days at 4 degrees C, followed by 16 hours at 25 degrees C and 8 hours at 37 degrees C. The dialysis solution used was Dianeal PD-2 with 1.5% dextrose. Samples were removed at intervals and analyzed by stability-indicating high-performance liquid chromatography. Under condition A, ceftazidime sodium alone was stable for 24 hours at 25 degrees C but only 2 hours when then heated to 37 degrees C. Under condition B, ceftazidime sodium alone was stable throughout the observation period. Teicoplanin sodium alone was stable throughout the observation periods under both conditions. In combination, the drugs were stable if initially refrigerated and then brought to room temperature one week later, but were unstable when initially stored at 25 degrees C. No visual changes were noted, and pH did not vary substantially. Ceftazidime 100 micrograms/mL (as the sodium salt) and teicoplanin 25 micrograms/mL (as the sodium salt) combined in a PD solution were unstable when first kept at 25 degrees C before storage at 37 degrees C. The drugs in the combination remained stable when the solution was kept at 4 degrees C before storage at 37 degrees C.

[Specificities of antibacterial activity of zwitterionic 7-methoxyimino cephems (cephalosporins of fourth generation]

Zwitterionic 7-methoxyimino cephalosporins possess a variable substitution at C3 which contains a quaternary nitrogen. These cephalosporins display low affinities for class I beta-lactamase and rapid penetration through the outer membrane of Gram negative bacilli. Hence, they remain active against some, but not all, ceftazidime-resistant Enterobacteriaceae. Antipseudomonas activities are generally similar to that of ceftazidime except that cefelidin is more active. The new zwitterionic compounds express greater antistaphylococcal potency than does ceftazidime. On the basis of structural and antibacterial characteristics the expression "forth generation" is acceptable to describe the wzitterionic 7-methoxyimino cephalosporins.

Stability of drug additives to peritoneal dialysate

OBJECTIVE

The primary literature was reviewed to determine the stability of drug additives in peritoneal dialysis solutions.

DATA SOURCES

A MEDLINE search and retrieval, covering the period 1981 to 1994, was undertaken to identify relevant original literature. Additional references were identified from citations within the original literature. Non-English literature was excluded unless an English abstract was provided.

STUDY SELECTION

Forty-nine studies were identified. Of these, 24 were directly related to drug stability, 13 were related to the clinical use of the drug additives but included no stability data, and 12 examined other, nonstability aspects of in vitro activity of antibiotics, additives, or drug adsorption in peritoneal dialysis bags and tubing.

DATA EXTRACTION

Data included concentrations of drug additives and dialysate solutions, duration and temperatures of storage conditions, types of assay, and whether they were stability-indicating.

RESULTS

Stability was defined as the duration of time that the drug concentration remained at 90% or more of the original concentration. Stability was examined under a large variety of conditions. Thirty-one drugs were identified from 20 manuscripts as single-drug additives. Most beta-lactams were stable for 1-2 weeks in a refrigerator and for several days at room temperature. Aminoglycosides were stable for 1-2 days at room temperature. Glycopeptides were stable for several weeks refrigerated or at room temperature. Prolonged storage at room temperature resulted in instability of cefotaxime, ceftazidime, ceftriaxone, and miconazole. Eleven drugs were identified from seven manuscripts as drug combination studies and showed similar stability as single agents. Dialysate concentration appeared to have minimal effect on stability.

CONCLUSIONS

Drug additives in peritoneal dialysate, singly or combined, should be avoided unless data are available to support their stability. Additives should be made as close as possible to the time of the exchange. Alternatively, additives should be stored refrigerated, then warmed prior to use. The practice of preparing numerous bags at one time should be avoided. Finally, stability data do not indicate sterile integrity of the dialysate.

Influence of pH, temperature, and buffers on the kinetics of ceftazidime degradation in aqueous solutions

First-order rate constants (k) were determined for the hydrolysis of ceftazidime in the pH range of 0.5 to 8.5 at 45, 55, and 65 degrees C by a stability-indicating HPLC assay. In the absence of buffer effects, the pH-rate expression was k = kH1f1(aH+) + kH2f2(aH+) + kH3f3(aH+) + kSf3 + kOHf3(aOH-), where KH and KOH are the catalytic rate constants for the activity of hydrogen (aH+) and hydroxyl (aOH-) ions, respectively, and kS is the rate constant for spontaneous hydrolysis. The fractions of ceftazidime in various stages of dissociation (f1, f2, and f3) were calculated from kinetically determined apparent Ka values of 2.03 x 10(-2) and 4.85 x 10(-5). Catalytic constants (kcat) were calculated for formate, acetate, phosphate, and borate buffers, which accelerated hydrolysis. Each of the rate constants (kH1, kH2, kH3, kS, kOH, and kcat) were described as a function of temperature with calculated A and E values in the Arrhenius equation, kT = Ae-E/RT. Ceftazidime hydrolysis rate constants (k) were calculated as a function of pH, temperature, and buffer by combining the pH-rate expression with the buffer contributions calculated from kcat values and the temperature dependencies. These equations and their parameter values successfully calculated 95 of 104 experimentally determined rate constants with errors of < 10%. Maximum stability was observed in the relatively pH-independent region from 4.5 to 6.5. Hydrolysis rate constants at 30 degrees C were predicted and experimentally verified for four ceftazidime solutions, three of which (pH 4.4 acetate buffer and pH 5.5 and 6.5 phosphate buffers) maintained 90% of their initial concentration for approximately 1.5 days.

Radical mechanisms of cephalosporins: a pulse radiolysis study

Radiosterilization induces radicals, and it is very important to describe radical mechanisms before the possible use of cephalosporins gamma sterilization. Moreover, physiological or radiotherapeutically induced free radicals also initiate radical mechanisms. For this study, pulse radiolysis was used. This method permits to avoid in vivo direct study difficulties of bioradical processes and gives quantitative data. Reactions of solvated electron (eaq-), hydroxyl radical (.OH), azide radical (N3.), dibromine radical anions (Br2.-), oxygen, and superoxide radical (O2.-) with three cephalosporins have been studied. Absorption spectra and rate constants have been determined. It has been found that both eaq- and .OH quickly react (k congruent to 10(10) mol-1 L s-1) with the molecules to give radicals with similar absorption spectra. N3. gives an absorption spectra that has been attributed to an electron transfer, whereas a part of .OH and Br2.- could add themselves to an unsaturated bond.

The influence of carbohydrates and polyhydric alcohols on the stability of ceftazidime in aqueous solution

The kinetics of degradation of ceftazidime in aqueous solutions containing various carbohydrates (glucose and fructose) or polyhydric alcohols (sorbitol and mannitol) was investigated over the pH range 9.92-10.93 at 35 degrees C. A relationship between the degradation rate and the hydroxy compound concentration was observed at each pH studied, and the rate-accelerating effect of the compounds was directly proportional to the hydroxide ion activity.

Kinetics of hydrolysis of ceftazidime in aqueous solutions

The kinetics of hydrolysis of ceftazidime in aqueous solutions at 323 K, 333 K, 343 K and 353 K over the pH-range (0.43-9.76) and at 295 K, 303 K and 308 K over the pH-range (9.17-13.16) has been investigated. The decomposition was followed by HPLC and UV spectral methods. The pH-rate profile was accounted for by the specific acid catalyzed reactions and also by assuming spontaneous water-catalyzed decomposition of molecule ceftazidime in various grade of dissociation. Various buffer substances were found to exhibit general acid and base catalysis of the degradation. Thermodynamic parameters of the reaction: energy, entropy and enthalpy of activation and the frequency factor for the specific rate constants were determined.

Stability and compatibility studies of cefaloridine, cefuroxime and ceftazidime with PVC infusion bags

A rapid isocratic technique was developed for the analysis of three cephalosporins: cefaloridine, cefuroxime and ceftazidime in parenteral solutions using high-performance liquid chromatography (HPLC) with UV detection and C18 column. The availability and compatibility of drugs from solutions infused via plastic infusion bags through plastic administration sets have been examined. No significant drugs loss was observed during the simulated infusions (n = 4) for 1 h using PVC infusion bags and administration sets. No significant difference was found between infusion solutions (5% glucose or 0.9% NaCl). The stability of drugs was also studied in solution in PVC bags after storage at room temperature and at +4 degrees C without protection from light. The results show the stability of drugs during 24 h at room temperature and 7 d storage at +4 degrees C to be satisfactory, irrespective of the infusion solution (5% glucose or 0.9% NaCl).

Stability of ceftazidime and vancomycin alone and in combination in heparinized and nonheparinized peritoneal dialysis solution

OBJECTIVE

To examine the stability of ceftazidime, vancomycin, and heparin, alone and in combination, in dialysis solution over six days at three temperatures.

DESIGN

Nine 250-mL Dianeal PD-2 dextrose 1.5% bags were prepared with ceftazidime, vancomycin, and heparin alone and in combination at set concentrations of 100 micrograms/mL, 50 micrograms/mL, and 1 unit/mL, respectively. Three bags of each mixture were stored at 4, 25, and 37 degrees C. Duplicate samples for analysis were removed from each bag at the following time points: premix, 0, 12, 24, 48, 72, 96, 120, and 144 hours.

MAIN OUTCOME MEASURES

Each sample was examined visually for signs of cloudiness and precipitation. Each sample was analyzed by stability-indicating HPLC assay for ceftazidime and vancomycin, with stability defined as less than 10 percent degradation of drug over time.

RESULTS

No color change or precipitation was observed in any bag. Vancomycin with or without heparin was stable for 5-6 days at 4, 25, and 37 degrees C. Ceftazidime with and without heparin was stable for 6 days at 4 degrees C, 4 days at 25 degrees C, and less than 12 hours at 37 degrees C. Vancomycin plus ceftazidime with and without heparin was stable for 6 days at 4 degrees C and 25 degrees C, and 4-5 days at 37 degrees C. Ceftazidime plus vancomycin with or without heparin was stable for 6 days at 4 degrees C, 2-3 days at 25 degrees C, and 12 hours at 37 degrees C.

CONCLUSIONS

Bulk preparations of ceftazidime and vancomycin, alone and in combination and with or without heparin in Dianeal PD dextrose 1.5% solution, are sufficiently stable for use up to 6 days under refrigeration or 48 hours at room temperature.

Electron spin resonance study of radiosterilization of antibiotics: ceftazidime

Fundamental information on radiosterilization of ceftazidime was obtained by electron spin resonance (ESR) measurement of free radicals produced in gamma-ray-irradiated ceftazidime at 4.2-295 K. Three types of free radicals are produced by gamma-irradiation. The first one shows septet lines in an ESR spectrum and decays at 230 K: it is assigned as a .C(CH3)2COOH radical. The second one shows triplet lines and decays at 293 K: it is assigned as iminoxyl radicals (> C = N-O.). The third one shows a broad singlet line and survives even at 295 K. The plausible assignment of this spectrum is discussed. It is concluded that an O-C bond of the gamma-irradiated ceftazidime is ruptured, producing the iminoxyl radicals and .C(CH3)2COOH radicals. The yields of free radicals increase linearly with the increasing dose of gamma-irradiation up to 10 kGy at 295 K as well as 77 K. Half of the radicals that show a broad singlet line survive at 295 K upon storage of the irradiated ceftazidime for 159 days. It is concluded that the ESR measurement of free radicals gives a good method for discrimination of irradiated antibiotics from non-irradiated ones and an estimation of an irradiation dose.

Stability of ceftazidime (with arginine) stored in plastic syringes at three temperatures

The stability of ceftazidime (with arginine) stored in plastic syringes at three temperatures was studied. Ceftazidime (with arginine) was reconstituted with sterile water for injection to a concentration of 100 mg/mL and transferred to plastic syringes. Syringes were stored at 22 degrees C for 24 hours; at 4 degrees C for 7 or 10 days, then at 22 degrees C for 24 hours; or at -20 degrees C for 91 days, then at 22 degrees C for 24 hours or at 4 degrees C for seven days followed by 22 degrees C for 24 hours. Ceftazidime concentration was measured at various times by using a stability-indicating high-performance liquid chromatographic method. At each sampling time, each syringe was visually inspected and the pH of each solution was measured. Mean ceftazidime concentration remained > 90% of initial concentration at all storage conditions. Although during storage the color of the solutions changed from light straw to dark yellow and the pH decreased, no precipitate was visually detected and no peaks for degradation products appeared on the chromatograms. Ceftazidime 100 mg/mL (with arginine) in sterile water for injection was stable when stored in plastic syringes for up to 24 hours at 22 degrees C, for 10 days at 4 degrees C followed by up to 24 hours at 22 degrees C, and for 91 days at -20 degrees C followed by up to 24 hours at 22 degrees C or by 7 days at 4 degrees C and up to 24 hours at 22 degrees C.

Stability of ceftazidime in plastic syringes and glass vials under various storage conditions

The stability of ceftazidime solutions (100 and 200 mg/mL) in plastic syringes and glass vials under various storage conditions was examined. Solutions of ceftazidime 100 and 200 mg/mL in sterile water were placed in polypropylene plastic syringes or glass vials and stored (1) at 21-23 degrees C for up to 8 hours, (2) at 4 degrees C for up to 96 hours, (3) at -20 degrees C for 28 days and then 21-23 degrees C for up to 8 hours, (4) at -20 degrees C for 28 days and then 4 degrees C for up to 96 hours, (5) at -20 degrees C for 91 days and then 21-23 degrees C for up to 8 hours, or (6) at-20 degrees C for 91 days and then 4 degrees C for up to 96 hours. Samples were withdrawn from each syringe and vial at designated times and assayed by high-performance liquid chromatography. Solutions were judged to be stable if drug concentrations remained above 90% of the initial values. The number of particles in each container under each storage condition was also evaluated. Ceftazidime was stable under all storage conditions. In all containers, particulate matter was within USP specifications for small-volume injections, with no change in particle count as a result of the freezing and thawing. Ceftazidime in sterile water in either glass vials or plastic syringes is stable for 8 hours at room temperature or 96 hours at 4 degrees C when such storage occurs (1) immediately after constitution, (2) after 28 days of frozen storage, or (3) after 91 days of frozen storage.

Stability of ranitidine hydrochloride with aztreonam, ceftazidime, or piperacillin sodium during simulated Y-site administration

The stability of ranitidine hydrochloride after being mixed with commonly used i.v. beta-lactam antibiotics and administered by simulated Y-site injection was studied. Solutions of ranitidine 1 mg/mL (as the hydrochloride salt), aztreonam 16.7 mg/mL, ceftazidime 20 mg/mL (with sodium carbonate), and piperacillin 30 mg/mL (as the sodium salt) were prepared by reconstitution in i.v. mini-bags. To simulate Y-site injection, 2 mL of ranitidine hydrochloride was mixed with 2 mL of each antibiotic in glass test tubes. These admixtures were prepared in triplicate and stored at room temperature under fluorescent light. Concentrations of each drug in each admixture were determined by stability-indicating high-performance liquid chromatography immediately and after one, two, and four hours. Aztreonam, ceftazidime, and piperacillin each retained more than 95% of the original concentration for at least four hours when mixed 1:1 with ranitidine. Ranitidine retained more than 90% of its original concentration for at least four hours when combined with each of the other drugs. Ranitidine 1 mg/mL (as the hydrochloride salt) and aztreonam 16.7 mg/mL, ceftazidime 20 mg/mL (with sodium carbonate), or piperacillin 30 mg/mL (as the sodium salt) were stable for at least four hours during simulated Y-site administration.

Compatibility of ceftazidime and aminophylline admixtures for different methods of intravenous infusion

OBJECTIVE

Aminophylline and ceftazidime are sometimes used concurrently in patients with respiratory disorders. Parenteral aminophylline usually is administered as a constant infusion, and ceftazidime is given intermittently or less commonly as a constant infusion. We evaluated the stability and compatibility of the two drugs when aminophylline is given as a constant intravenous infusion and ceftazidime is administered simultaneously either through a y-site (piggyback method) or as a continuous infusion (constant infusion method).

DESIGN

The chemical stability of intravenous aminophylline and ceftazidime in dextrose 5% and NaCl 0.9% for both methods was studied. Three different formulations of ceftazidime from the same manufacturer were studied (minibag using reconstituted ceftazidime, premixed minibag, and ceftazidime arginine). For the piggyback and constant infusion methods, samples were collected at 0, 1, and 2 hours; and 0, 6, and 24 hours, respectively. All experiments were conducted in triplicate. Samples were analyzed in duplicate by a stability-indicating HPLC assay method.

OUTCOME MEASURE

Ceftazidime and aminophylline were considered stable if concentrations remained above 90 percent of the original concentrations over the time periods studied.

RESULTS

Ceftazidime was determined to be compatible with aminophylline in the piggyback method. In contrast, when aminophylline and ceftazidime were admixed in the same intravenous container (constant infusion method), the two drugs were not stable.

CONCLUSIONS

These data indicate that aminophylline and ceftazidime admixtures are incompatible when prepared in the same intravenous container, which may occur if both are given as a constant infusion. The two drugs are compatible when the ceftazidime is piggybacked into a primary intravenous set in which aminophylline is administered as a constant infusion.

Gas production of three brands of ceftazidime

Two sodium carbonate formulations of ceftazidime (Tazidime and Tazicef) and a new arginine formulation (Ceptaz) were evaluated for gas production and bubble formation within the drug reservoir and extension tubing of a portable infusion pump during a 24-hour delivery cycle. Triplicate samples of each brand of ceftazidime were studied under identical conditions. All formulations were constituted and diluted with sterile water for injection to a concentration of approximately 33 mg/mL, drawn into syringes, and expelled into infusion-pump drug reservoirs. Triplicate samples of degassed Tazidime and Tazicef were evaluated in the same manner. In one set of triplicate experiments, reservoirs for each formulation were attached to portable infusion pumps immediately after filling at room (23 degrees C) temperature and were programmed to deliver 25 mL over one hour every eight hours for a 24-hour delivery cycle. In a second experiment, reservoirs containing triplicate samples of each product were refrigerated (3 degrees C) for 24 hours before they were attached to the pumps for dose delivery. Visual observations were made for all pumping devices. In addition, multiple vials of each formulation were constituted, and the headspace pressure of the various formulations was monitored to compare the pressure build-up due to carbon dioxide. The presence of carbon dioxide was confirmed by gas chromatography. Pressure build-up due to carbon dioxide formation occurred in the ceftazidime sodium carbonate vials only. The sodium carbonate formulations required degrassing to reduce gas and bubble formation to a manageable level after constitution. Additionally, drug was lost because of spewing of some samples during withdrawal from the vial.(ABSTRACT TRUNCATED AT 250 WORDS)

Stability of ceftazidime and amino acids in parenteral nutrient solutions

The stability of ceftazidime was studied under conditions simulating administration via a Y-injection site into a primary infusion of parenteral nutrient (PN) solution; the stabilities of ceftazidime and amino acids when the drug was added directly to PN solutions were also studied. Three PN solutions containing 25% dextrose were used; the amino acid contents were 0, 2.5%, and 5%. Ceftazidime with sodium carbonate was used to prepare stock solutions of ceftazidime 40 mg/mL in both 0.9% sodium chloride injection and 5% dextrose injection; to simulate Y-site injection, samples were added to the three PN solutions to achieve ceftazidime concentrations of 10 and 20 mg/mL, or 1:1 and 1:3 ratios of drug solution to PN solution. Samples of these admixtures were assayed by high-performance liquid chromatography (HPLC) initially and after room-temperature (22 degrees C) storage for one and two hours. Additional solutions were prepared by adding sterile water for injection to ceftazidime with sodium carbonate; drug solutions were added to each PN solution in polyvinyl chloride bags to achieve ceftazidime concentrations of 1 and 6 mg/mL. The samples were assayed by HPLC for ceftazidime concentration after storage at 22 degrees C for 3, 6, 12, 24, and 36 hours and at 4 degrees C for 1, 3, 7, and 14 days. Amino acid stability was analyzed in admixtures containing 5% amino acids and ceftazidime 6 mg/mL after 24 and 48 hours at 22 degrees C and after 7 and 10 days at 4 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

In-vitro and in-vivo antimicrobial activities of a novel cephalosporin derivative, CP6162, possessing a dihydroxypyridone moiety at the C-3 side chain

The antibacterial activity of a novel cephalosporin derivative, CP6162, possessing a dihydroxypyridone moiety at the C-3 side chain, was evaluated in vitro and in vivo, with ceftazidime, aztreonam and cefoperazone as the reference antibiotics. CP6162 showed weak or little activity against Gram-positive bacteria, but potent activity against clinical isolates of the Gram-negative species including strains of Pseudomonas aeruginosa, Ps. cepacia, Acinetobacter sp., Xanthomonas maltophilia, Serratia marcescens, Enterobacter cloacae and Citrobacter freundii, which were resistant to the reference antibiotics. The MICs of CP6162 were only slightly affected by the high producers of beta-lactamases except for cephalosporinase-producing C. freundii. It was, however, affected by the presence of ferric ion. CP6162 showed in-vivo activity paralleling the in-vitro activity, and also showed pharmacokinetic parameters similar to those of ceftazidime in mice and rats.