Measurement of cefaclor and amoxicillin-clavulanic acid levels in middle-ear fluid in patients with acute otitis media.

Concentrations of cefaclor (CFC) or amoxicillin-clavulanic acid (AMX/CA) in middle-ear fluid collected preserving the stability and clearing the cell contents has been compared to those obtained using the traditional method. Sixty-seven children with effusive otitis media were treated orally with CFC (20 mg/kg of body weight) or AMX/CA (20 mg/kg) (4:1 ratio). The concentrations in cell-free fluid (C-) appear higher than those in the total fluid (C+) (as assayed traditionally).

Stability and in vitro efficacy of antibiotic-heparin lock solutions potentially useful for treatment of central venous catheter-related sepsis.

OBJECTIVES: Increasing numbers of patients for whom infection is a major risk are dependent on central venous catheters. Antibiotic-anticoagulant locks may have a role in preventing or treating catheter-related infections. The aim of this study was to determine the in vitro stability and efficacy of antibiotic-heparin lock solutions. METHODS: Candidate antibiotics (amikacin, ciprofloxacin, flucloxacillin, gentamicin, linezolid, teicoplanin) were investigated in vitro, either individually or in combination, in solution with heparin. The solutions were initially tested for visual precipitation. The efficacy of stable solutions and taurolidine was then tested in a catheter model bioassay system against microorganisms commonly encountered in catheter-related septicaemia. RESULTS: In general, lower concentrations of heparin (

HPLC for in-process control in the production of sultamicillin.

A high-performance liquid chromatographic assay coupled with UV detection (215 nm) was developed for the determination of sultamicillin and its synthesis precursors. The separation of the analytes was performed on a Kromasil C(18) column (15 cm x 4.6 mm i.d., 5 microm) at 20 degrees C. The mobile phase (25 mM phosphate buffer, pH 7.0 and acetonitrile 48%) was pumped at a flow rate of 1.0 ml min(-1). This method is sensitive (limits of detection ranged between 0.4 and 1.2 mg l(-1)) and selective for the determination of sultamicillin and could be used for monitoring different synthetic routes.

CE versus LC for simultaneous determination of amoxicillin/clavulanic acid and ampicillin/sulbactam in pharmaceutical formulations for injections.

A rapid, capillary electrophoresis method was evaluated for determination of amoxicillin and clavulanic acid in Augmentin as well as ampicillin and sulbactam in Unasyn preparations for injections. Phosphate-borate buffer at pH 8.66 containing 14.4% sodium dodecyl sulfate was used as a mobile phase. The method was validated. Reproducibility, precision, accuracy and assay linearity in concentration of amoxicillin 0.05-3.03 mg/ml and ampicillin 0.05-3.08 mg/ml, as well as clavulanic acid 0.02-2.02 mg/ml and sulbactam 0.05-2.08 mg/ml were established. This new method is fast, inexpensive and limits consumption of organic solvents when compared with alternative high performance liquid chromatography (HPLC) method, used for drug analysis. Statistical analysis by Student's t-test showed no significant differences between the results obtained by the two methods t(calculated) 0.32 and 1.69 for amoxicillin and clavulanic acid and 0.67 and 1.93 for ampicillin and sulbactam were smaller than t(tabulated).

The dissolution kinetics of sulfamethoxazol, trimethoprim and oxytetracycline hydrochloride from multicomponent solid dispersion capsules ("Sulfoxytrim").

Release profiles and dissolution kinetics of active substance, viz. sulfamethoxazol (SMO), trimethoprim (TMP), and oxytetracycline hydrochloride (OTC) from capsulated multicomponent dispersions was studied in a flow-cell apparatus at 37 degrees C by using a dissolution medium of 0.1 mol/l HCl. The results revealed that the relative dissolution efficiency (DE) and dissolution profiles of one active ingredient were affected by the presence of the two others. Vitamin C added caused the decreased the dissolution rate constants (K) and DE--values of all the active substances studied.

UV-spectrophotometric determination of ampicillin sodium and sulbactam sodium in two-component mixtures.

A simple spectrophotometric method is used for the resolution of the binary mixtures of ampicillin sodium and sulbactam sodium. In aqueous solution, zero-order spectra are subject to interference, so first-derivative spectrophotometry was used to enhance the spectral details allowing the determination of ampicillin sodium from the signal at the zero-crossing point for sulbactam sodium at 268 nm. In 0.1 N sodium hydroxide, sulbactam sodium was determined from the absorbance at 260 nm with negligible contribution from ampicillin sodium. Also, sulbactam sodium was determined without interference using first- and second-derivative spectra in 0.1 N sodium hydroxide at 276 nm (peak-height) and 262-284 nm (peak-to-peak), respectively. The method is rapid, simple, does not require a separation step and allows the determination of each drug without interference from the other. The proposed method has been applied successfully to the assay of these drugs in mixtures and in commercial injections.

Amoxicillin and clavulanic acid concentrations in gingival crevicular fluid.

The beta-lactams are bactericidal antibiotics, but some of them may be inactivated by bacterial beta-lactamases which destroy the beta-lactam ring. The inactivation of amoxicillin by beta-lactamases of gram negative anaerobic bacteria can be circumvented by the addition of clavulanic acid, a beta-lactamases inhibitor. Thus, most of these bacteria are susceptible to this combination. The aim of this study was to investigate the concentrations of amoxicillin and clavulanic acid in gingival crevicular fluid (GCF). These concentrations were measured in 20 patients with rapidly progressive periodontitis 1 h after a dose of 500 mg (1 tablet Augmentin) on day 0 and 1 h after the 10th intake on day 3. For the sampling of GCF, Periopapers were introduced in 16 gingival sites per subject and time. The GCF volumes collected were estimated using the Periotron 6000. A high performance liquid chromatography method has been developed for the determination of amoxicillin and clavulanic acid in microsamples (1 to 10 microliters) of GCF. The concentrations of amoxicillin and clavulanic acid were respectively, 14.05 micrograms ml-1 and 0.40 microgram ml-1 at day 0, 13.93 micrograms ml-1 and 0.37 microgram ml-1 at day 3. Effective levels of amoxicillin and clavulanic acid, well above the minimal inhibitory concentrations of some susceptible periodontal anaerobes (P. intermedia) involved in destructive periodontal diseases, are achieved following the multiple administration of amoxicillin combined with clavulanic acid.

Simultaneous determination of amoxycillin and clavulanic acid in pharmaceutical products by HPLC with beta-cyclodextrin stationary phase.

A simple, rapid and accurate method for simultaneous determination of amoxycillin and clavulanic acid using HPLC with beta-cyclodextrin stationary phase was developed. It involves the use of tetraethylammonium acetate (TEAA) as an additive reagent, methanol-buffer solution (pH 4.5) (35:65; v/v) as the mobile phase, detection at 225 mm and chromatogram within 12 min. Linearity and precision of the internal standard method have been obtained. Recoveries ranged from 99.25 to 105.63% for amoxycillin in the synthetic mixture. For clavulanic acid it was from 99.50 to 101.64%. This method is convenient and reproducible for analyses of these two components in different dosage forms.

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.

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.

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.

Determination of imipenem and cilastatin sodium in Primaxin by first order derivative ultraviolet spectrophotometry.

A UV-spectrophotometric assay to measure the concentrations of the active drug components (imipenem and cilastatin) or Primaxin for routine release testing is described. The assay is based on the use of first order derivative spectrophotometry. The trough amplitudes in the first derivative spectrophotometric spectra at 243 and 318 nm were selected to determine cilastatin and imipenem, respectively. A linear relationship (R > 0.99) between the trough amplitudes and concentrations was demonstrated over the range 14-42 micrograms ml-1 for both drug components. Commercial IV formulations and laboratory prepared mixtures containing both drugs in different proportions were assayed using the developed method with good recoveries (ave. 100.6%). The method is rapid, precise, accurate and was shown to be equivalent to the more time consuming LC method; which is currently used for routine release testing. The specificity and stability indicating properties of the method will also be addressed.

Penetration of amoxycillin/clavulanic acid into bronchial mucosa with different dosing regimens.

BACKGROUND: The efficacy of an antibiotic is related to its concentration at the site of infection. Previous studies of the concentrations of amoxycillin and clavulanic acid (co-amoxiclav) in respiratory secretions or whole lung tissue have suffered from methodological problems. The concentration of amoxycillin and clavulanic acid was determined in bronchial mucosal biopsy samples obtained at bronchoscopy following five different dosing regimens. METHODS: Bronchial biopsy and serum samples were obtained from 50 patients undergoing diagnostic bronchoscopy. Ten patients each received 375 mg, 625 mg, 750 mg, and 3.25 g oral, and 1.2 g intravenous co-amoxiclav 1-3 hours before bronchoscopy. The concentrations of clavulanic acid and amoxycillin were determined by high performance liquid chromatography using a microbore column, solid phase extraction, and preconcentration to improve sensitivity tenfold over previous methods. RESULTS: Concentrations of both clavulanic acid and amoxycillin in bronchial mucosa were dose related and were well above the MIC90 of co-amoxiclav for the common bacterial respiratory pathogens including Haemophilus influenzae, Micrococcus catarrhalis and Streptococcus pneumoniae for all dosing regimens. Mean mucosal levels were 200% and 118% of the corresponding serum levels for amoxycillin and clavulanic acid respectively. CONCLUSIONS: Amoxycillin and clavulanic acid are concentrated in bronchial mucosa and, even at the lowest dose of 375 mg orally, are likely to produce tissue levels in the lung sufficient to inhibit all the common community acquired respiratory pathogens.

Ampicillin and ampicillin-sulbactam dilution tests with mixed cultures of Bacteroides fragilis, Escherichia coli and Enterococcus.

Bacterial interactions in mixed infections may compromise antimicrobial therapy. The in vitro bactericidal activity of ampicillin and ampicillin-sulbactam against aerobic/anaerobic mixed cultures of Bacteroides fragilis, Escherichia coli and Enterococcus spp. was studied by means of broth dilution tests. The MBC of ampicillin for Enterococcus faecalis 6 was 0.25 mg/l when tested singly; in association with B. fragilis 1, however, the MBC for E. faecalis 6 was 16 mg/l. When tested singly E. coli 9 and B. fragilis 1 were both killed by ampicillin at a concentration of 4 mg/l in combination with 1 mg/l sulbactam. When both strains were associated, the MBC for B. fragilis 1 rose to > 256 mg/l. Results obtained indicate that the behaviour of bacteria as determined in pure cultures is not necessarily identical with the antibiotic susceptibility present in mixed cultures. It was shown that, besides beta-lactamase production by involved bacteria, other factors contribute to the alteration of bacterial susceptibility in mixed cultures. Synergistic and antagonistic effects between associated organisms were observed. For example, it was found that two moderately sensitive bacterial strains were resistant in mixed culture.

A high performance liquid chromatography system for the simultaneous assay of some antibiotics commonly found in combination in clinical samples.

Using a single reversed-phase HPLC column with a mobile phase of methanol and 100 mM phosphate buffer, concentrations of seven antibiotics (chloramphenicol, metronidazole, cefuroxime, cephalexin, ceftazidime, ampicillin and benzylpenicillin) which are commonly used clinically in combinations of two or more, can be assayed and results reported within one hour. No endogenous interference was detected in serum, urine or cerebrospinal fluid. The method was highly specific even in the presence of other drugs and metabolites commonly found in clinical samples and provides a rapid, simple technique suitable for use in routine microbiological practice.

Antibiotic persistence and tolerance in the lactating sheep following a course of intramammary therapy.

The commercial use of sheep for the production of milk and milk products is attractive to farmers actively diversifying their dairy interests due to the impact of the quota system. As intensification of milking increases, flock sizes will enlarge and the incidence of ovine mastitis will inevitably increase. The pharmaceutical industry and the veterinary practitioner will be required to provide advice and data upon the performance of currently available bovine intramammary preparations for the sheep. This study produces evidence to confirm that one available bovine intramammary preparation, when infused into milking sheep, produced a withholding time approximately three times as long as that defined for the cow. Following a course of three infusions over a period of 24 hours after consecutive milkings, milk was not acceptable for human consumption or for the production of cheese and yoghurts until 136 hours following the final infusion. This situation is likely to be representative of that which will occur with other intramammary products used in the ovine species following infusion with bovine intramammary preparations.