Microcalorimetric evaluation of the in vitro compatibility of amoxicillin/clavulanic acid and ampicillin/sulbactam with ciprofloxacin.

Solution calorimetric technique has been used to determine the compatibility of binary and ternary systems of ampicillin trihydrate (AMP), sulbactam sodium (SS), amoxicillin trihydrate (AM), potassium clavulanate (PC) and ciprofloxacin hydrochloride (CP). The enthalpy of solution (DeltasolH) were obtained over a wide range of composition in the pH range 2-9. For all the pure drugs the DeltasolH is endothermic in nature. The molar enthalpies of interaction of binary (DeltaHbi.E) and ternary (DeltaHter.E) mixtures of the drugs in aqueous buffers have been determined. The DeltaHbi.E for all binary systems is negative and pH dependent (maximum pH 6-8) indicating the interaction among charged species of the drugs. In case of binary systems with CP the magnitude of DeltaHbi.E indicate strong interactions. The variation and magnitude of DeltaHbi.E for the systems is discussed in terms of hydrogen bonding and van der Waal's interaction in the solution. The interaction parameter for ternary systems (A) is positive indicating repulsive interaction among the drugs. The coefficients hi's calculated from Redlich-Kister equation for binary systems (DeltaHbi.E) and ternary interaction parameter (A) were used to predict the compatibility of the marketed formulations in pH range studied.

An in vitro study on the compatibility and precipitation of a combination of ciprofloxacin and vancomycin in human vitreous.

AIMS: To investigate the precipitation process of a mixture of vancomycin and ciprofloxacin by equilibrium dialysis and its subsequent effect on the level of available free antibiotics. METHODS: Concentrations of vancomycin and ciprofloxacin in an equilibrium dialysis chamber were measured during the equilibrium process by high performance liquid chromatography and fluorescence polarisation immunoassay. Normal saline (NS), balanced salt solution plus (BSS Plus), and vitreous were used separately as the medium of dialysis. RESULTS: Precipitation of ciprofloxacin occurred on incubation at 37 degrees C. It formed precipitate on its own or when mixed with vancomycin in all the three media of NS, BSS Plus, and vitreous. There was more precipitation at higher initial ciprofloxacin concentrations; at 25.0 mg/l about 75% free drug in BSS Plus was lost after 72 hours. The extent of precipitation was similar in both NS and BSS Plus. In the dialysis chambers, 20 mg/l ciprofloxacin dialysed against 125 mg/l vancomycin was reduced to a concentration about 5.0 mg/l after 168 hours. Precipitation of vancomycin was negligible. Ciprofloxacin precipitated in vitreous at body temperature, irrespective of the presence of vancomycin. Even after precipitation, the resultant concentration of ciprofloxacin was still higher than the MIC(90) of the drug against most Gram negative organisms. CONCLUSIONS: Based on this in vitro study, ciprofloxacin precipitated in vitreous at body temperature, irrespective of the presence of vancomycin or the medium for intravitreal injection. The resultant amount of ciprofloxacin was still higher than the MIC(90) of the drug against most Gram negative organisms after precipitation. The authors suggest ciprofloxacin in place of ceftazidime when used in combination with vancomycin for treatment of infective endophthalmitis.

Development of a long-lasting ventricular catheter impregnated with a combination of antibiotics.

A ventricular silicone catheter impregnated with a combination of rifampin and a quinolone was developed in order to prevent ventricular shunt related infections. As model substance for the quinolones we used sparfloxacin, because of its specific physicochemical properties resulting in a quantitative detection also in the presence of a second antibiotic. In our study we focused especially on an optimization of the antibiotic release out of the impregnated catheters in order to develop long lasting devices with a broad antimicrobial spectrum. A release-optimized catheter was tested with an in vitro colonization test and additionally with a method developed to examine the spread of bacteria on a catheter surface. In vitro experiments showed that the impregnated catheters reduce the colonization with Staphylococcus epidermidis for at least 1 year and prevent the spread of bacteria along the catheter surface.

Application of micellar electrokinetic chromatography to the determination of sultamicillin in oral pharmaceutical preparations.

A micellar electrokinetic capillary electrophoretic method for determination of sultamicillin in Unasyn oral preparations--tablets and suspension--was evaluated. Phosphate-borate buffer at pH 7.0 containing 1.0% sodium dodecylsulfate was used as a mobile phase. The elaborated method ensures separation of sultamicillin from p-toluenesulfonic acid and the impurities, ampicillin, sulbactam and penicillamine. The method was validated for specificity, reproducibility, precision, accuracy and assay linearity (in a concentration range of sultamicillin of 0.05-1.5 mg/ml). Statistical analysis by Student's t-test showed no significant differences between the results obtained by micellar electrokinetic chromatography and HPLC, t(calculated) 0.519 for suspension assays and 0.284 for tablets assays were smaller then t(tabulated).

Additive, indifferent and antagonistic effects in combinations of epigallocatechin gallate with 12 non-beta-lactam antibiotics against methicillin-resistant Staphylococcus aureus.

Additive, indifferent and antagonistic effects were observed in combinations of epigallocatechin gallate (EGCg, a main constituent of tea catechins) with12 non-beta-lactam antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). The combinations of EGCg with the inhibitors of either protein or nucleic acid synthesis showed additive or indifferent effects. These antibiotics included tetracycline, minocycline, chloramphenicol, streptomycin, gentamicin, kanamycin, erythromycin, rifampicin and ofloxacin. In contrast, EGCg showed an antagonistic tendency against glycopeptide antibiotics (vancomycin, teicoplanin and polymyxin B). The common property of these antibiotics is the peptide backbone structure, suggesting a direct binding of EGCg with the antibiotics. The above results indicate that tea catechins may affect the activities of antibiotics both positively and negatively.

[Novel compounds active on staphylococci]. / Les nouveaux antistaphylococciques.

Research efforts to discover new compounds active against staphylococci are more than ever justified today. The incidence of methicillin-resistant staphylococci remains very high in hospitals, and the solution provided by glycopeptides is far from being satisfactory. These compounds exhibit mediocre pharmacokinetic and pharmacodynamic properties. Their ease and safety of use are poor. Finally, strains with diminished sensitivity to these antibiotics are beginning to appear. This article examines the opportunities offered by two new anti-staphylococcal agents: quinupristine-dalfopristine (Synercid) and linezolide (not marketed in France).

Beta-lactamase-inhibitor combinations in the 21st century: current agents and new developments.

Combinations of beta-lactams and beta-lactamase inhibitors have become one of the most successful antibacterial strategies in our global battle against bacterial infections. The success of these agents is particularly emphasized by the continued efficacy of Augmenting (amoxicillin and clavulanate) after nearly 20 years of clinical use. The clinical situation now dictates that second-generation beta-lactamase inhibitors capable of encompassing both class A and class C beta-lactamases would combat emerging resistance and provide a vital addition to our armory of hospital antibiotics. This realization has generated a renewed interest in beta-lactamase inhibitors and improved the prospects for the delivery of such agents in the future.

[Antibiotic management of acute otitis media. New recommendations]. / Prise en charge antibiotique de l'otite moyenne aiguë. De nouvelles précisions.

FAILURES OF ANTIBIOTIC TREATMENT: The number of failures after treatment of acute middle ear infections with the 2 main antibiotics prescribed (amoxicillin and the combination amoxicillin-clavulanic acid) is on the rise. These failures appear to be related to increased resistance of the 2 principal pathogens, pneumococci and Hemophilus influenzae. A NEW FORMULATION: In order to reduce the rate of failure, it has been necessary to both increase the dose of penicillin to overcome the reduced susceptibility of pneumococci to penicillin and to prescribe a beta-lactam because of the frequent isolation of beta-lactamase producing Hemophilus influenzae. A new formulation has been developed where the amoxicillin-clavulanic acid dose is 14 to 1. This allows a daily dose of 80 mg/kg for amoxicillin and 6.4 mg/kg for clavulanic acid. In one open multicentric study including 51 pediatric patients aged 3 to 48 months with acute middle ear infections, it was demonstrated that this new formulation can be very effective in eradicating the causal agents of acute middle ear infections, including pneumococci and penicillin-resistant Hemophilus. RECOMMENDATIONS FOR GOOD EFFICACY: Amoxicillin must always be prescribed, either alone or in combination with clavulanic acid, at the dose of 45 to 50 mg/kg b.i.d. the amoxicillin-clavulanic acid combination should be preferred for children under 2 years due to the risk of beta-lactamase producing Hemophilus.

Treatment of vancomycin-resistant enterococci, with a focus on quinupristin-dalfopristin.

Enterococci are the second most common cause of hospital-acquired infections, and drug resistance among these organisms is a growing problem. Vancomycin-resistant enterococci (VRE) now account for 7.9% of the nosocomial enterococcal infections. There is no standard therapy for VRE. Although some agents have shown in vitro activity alone or in combination, including ciprofloxacin, doxycycline, novobiocin, teicoplanin, chloramphenicol, and rifampin, treatment options are limited to combinations of drugs with marginal efficacy against the pathogens. Quinupristin-dalfopristin is a new investigational agent with activity against gram-positive cocci, including VRE.

Stability of amoxicillin-clavulanate in BACTEC medium determined by high-performance liquid chromatography and bioassay.

The stabilities of amoxicillin (16 micrograms/ml) and clavulanate (8 micrograms/ml), alone and in combination in BACTEC medium (Middlebrook 7H12B medium), were determined by high-performance liquid chromatography (HPLC) and bioassay. By HPLC, the half-life of amoxicillin (trihydrate and sodium) in combination with clavulanate in nonradiolabelled 7H12B medium was 6.7 days, whereas the half-life of clavulanate in combination with amoxicillin was 2.0 days. By bioassay, the half-lives of amoxicillin trihydrate and clavulanate in radiolabelled 7H12B medium were comparable (7 and 2 days, respectively) to those determined by HPLC. When clavulanate was tested alone, the half-life was determined to be 1.88 days by HPLC and 1.87 days by bioassay. The relatively short half-life of clavulanate can be adjusted by a procedure of "topping up," or adding one-half the concentration of clavulanate every second day, in order to allow accurate amoxicillin-clavulanate MIC testing with the BACTEC mycobacterial susceptibility system.

Piperacillin-Tazobactam: a new beta-lactam-beta-lactamase inhibitor combination.

We reviewed the spectrum of activity, pharmacokinetics, clinical efficacy, adverse effects, and relative advantages of piperacillin-tazobactam, a new beta-lactam-beta-lactamase inhibitor. Piperacillin-tazobactam has a wide spectrum of activity that includes gram-positive organisms such as staphylococci and streptococci, as well as many gram-negative aerobic and anaerobic bacteria. The combination distributes rapidly after parenteral administration and penetrates well into skin, lung, and intestinal mucosa. Compared with other beta-lactam-beta-lactamase inhibitor combinations, piperacillin-tazobactam has comparable efficacy in the treatment of intraabdominal infections, skin and soft tissue infections, and upper and lower respiratory tract infections. It may have better in vitro activity than the currently available combinations against selective bacteria that produce class I beta-lactamases (Richmond-Sykes classification). The combination is well tolerated, with diarrhea being the most common reported adverse effect. Additional controlled trials and clinical experience are required to define its role in clinical practice.

Analysis of binary mixtures of cephalothin and cefoxitin by using first-derivative spectrophotometry.

A method for the analysis of two-component mixtures of cephalothin and cefoxitin using zero-crossing first-derivative spectrophotometry is described. This technique permits the quantification of these drugs with closely overlapping spectral bands without any separation step. Linear calibration graphs of first-derivative values at 235.00 and 236.75 nm for cephalothin and cefoxitin, respectively, with negligible intercepts were obtained versus concentration in the range 4.0-32.0 micrograms ml-1 for both antibiotics. This paper presents a systematic examination of the experimental data by applying an exhaustive statistical analysis to demonstrate the validity of the method. The results of the determination of these antibiotics in mixtures of injectable dosage forms are also presented, together with their determinations in physiological serum and glucosed physiological serum.

Randomized, double blind comparison of brand and generic antibiotic suspensions: I. A study of taste in adults.

BACKGROUND: A belief that brand oral liquid medications taste better than their generic counterparts may influence prescribing habits among pediatricians. METHODS: We undertook a prospective, randomized, double blinded, comparative evaluation of the taste of brand and generic erythromycin ethylsuccinate, cephalexin monohydrate, erythromycin ethylsuccinate/sulfisoxazole, penicillin V potassium and trimethoprim-sulfamethoxazole in 42 adult volunteers. Subjects tasted one class of brand and generic antibiotics and rated them according to smell, texture, taste and aftertaste. RESULTS: At least one generic preparation of cephalexin, erythromycin ethylsuccinate/sulfisoxazole and penicillin V potassium was rated equal in taste to the respective brand name products. However, brand erythromycin estolate and trimethoprim-sulfamethoxazole name brand suspensions rated significantly higher than the other products tested. CONCLUSIONS: Based on our results brand name oral antibiotic formulations do not necessarily taste better than their generic counterparts.

Randomized, double blind comparison of brand and generic antibiotic suspensions: II. A study of taste and compliance in children.

BACKGROUND: The taste of oral liquid medications influences compliance in children. Generic preparations are prescribed to reduce cost and may taste worse than brand name products. METHODS: This was a prospective, randomized, double blind, crossover trial of the differences in taste and compliance between brand and generic antibiotic suspensions in children 3 to 14 years of age. Verbal and visual assessment methods were used to assess taste, and compliance was measured by the amount of drug returned after use. RESULTS: Ten children in each of the cephalexin and erythromycin-sulfisoxazole groups did not report that the brand and generic formulations tasted differently. Fifteen children thought that brand trimethoprim-sulfamethoxazole tasted better than the generic preparation. CONCLUSIONS: Brand name oral liquid antibiotics do not necessarily taste better than their generic counterparts. Despite preference for the taste of brand trimethoprim-sulfamethoxazole, all of the children in this study were compliant with both brand and generic medications.

Determination of ternary mixtures of antibiotics, by ratio-spectra zero-crossing first- and third-derivative spectrophotometry.

The ratio-spectra zero-crossing first- and third-derivative spectrophotometry have been used for determining ternary mixtures of penicillin-G sodium, penicillin-G procain and dihydrostreptomycin sulphate salts. The procedures are accurate, nondestructive and do not require resolutions of equations. In both methods, calibration graphs are linear, with zero-intercept, up to 30 micrograms ml-1 of penicillin-G sodium and penicillin-G procain, and up to 42 micrograms ml-1 of dihydrostreptomycin sulphate. r = 0.9999 in each instance. Working wavelengths, 218.5, 211 and 236 nm, respectively, in the first-derivative mode, and 222.5, 311.5 and 242 nm in the third-derivative mode. Detection limits for each drug at p = 0.01 level of significance were calculated to be 0.058, 0.010 and 0.014 micrograms ml-1 and 0.14, 0.012 and 0.34 micrograms ml-1, in the first- and third-derivative methods, respectively. Both methods apply favorably to either laboratory mixtures or commercial injections.

Stability of aztreonam and ampicillin sodium-sulbactam sodium in 0.9% sodium chloride injection.

The stability of aztreonam, ampicillin sodium, and sulbactam sodium admixed in 0.9% sodium chloride injection and stored at room temperature and under refrigeration was studied. Each of the following admixtures was prepared in 0.9% sodium chloride injection: (1) aztreonam 10 mg/mL; (2) ampicillin 20 mg/mL (as the sodium salt) and sulbactam 10 mg/mL (as the sodium salt); and (3) aztreonam 10 mg/mL, ampicillin 20 mg/mL, and sulbactam 10 mg/mL. Three minibags of each admixture were stored at room temperature and three were refrigerated. Every 12 hours, up to 96 hours, the admixtures were visually inspected and 5-mL samples were withdrawn for high-performance liquid chromatography and pH testing. No color change or precipitation was observed in any sample. In admixtures containing ampicillin, ampicillin was the first or only drug to lose more than 10% of initial concentration. In the ampicillin-sulbactam admixture, ampicillin was stable for 32 hours at room temperature and 68 hours refrigerated. In the aztreonam-ampicillin-sulbactam admixture, ampicillin was stable for 30 hours at room temperature and 94 hours refrigerated. Aztreonam 10 mg/mL, ampicillin 20 mg/mL (as the sodium salt), and sulbactam 10 mg/mL (as the sodium salt) in 0.9% sodium chloride injection were stable in combination for up to 30 hours at room temperature and 94 hours under refrigeration.

Compatibility of piperacillin sodium plus tazobactam with selected drugs during simulated Y-site injection.

The compatibility of piperacillin sodium plus tazobactam with selected drugs during simulated Y-site administration was studied. A 5-mL sample of piperacillin sodium 40 mg/mL plus tazobactam 5 mg/mL (Zosyn) in 5% dextrose injection was combined with a 5-mL sample of each of 75 other drugs at concentrations used clinically. Each combination was prepared in duplicate in glass culture tubes, with the order of mixing being reversed between the duplicates; storage was in constant fluorescent light at 22 degrees C. The admixtures were examined visually in normal fluorescent light and in high-intensity light zero, one, and four hours after preparation. A turbidimeter was used to measure the turbidity of each drug combination at the same intervals. Samples showing visual or turbidimetric evidence of incompatibility were subjected to particle sizing and counting. The majority of the drugs tested were compatible with Zosyn injection; most combinations had a turbidity of less than 0.1 nephelometric turbidity unit. However, 24 drugs exhibited various incompatibilities, including increased turbidity, particulate formation and precipitation, and color change. Piperacillin sodium 40 mg/mL plus tazobactam in 5% dextrose injection was visually compatible with the majority of the drugs tested for up to four hours at 22 degrees C but incompatible with 24 drugs.

The chemistry, pharmacokinetics and tissue distribution of piperacillin/tazobactam.

The pharmacokinetic properties of piperacillin/tazobactam are summarized. The data on piperacillin show that the behaviour of this well established agent is the same when given in combination with tazobactam as when given alone. Tazobactam shows pharmacokinetic characteristics typical of a beta-lactam compound. It distributes mainly into the extracellular space and shows typical tissue penetration behaviour. The tissue concentrations of piperacillin and tazobactam and their pharmacokinetic profiles in plasma and tissues encourage the view that the synergy observed in vitro will be reflected in clinical use.