Development of spectrofluorimetric method for determination of certain aminoglycoside drugs in dosage forms and human plasma through condensation with ninhydrin and phenyl acetaldehyde.

A simple and sensitive spectrofluorimetric method has been developed and validated for determination of amikacin sulfate, neomycin sulfate and tobramycin in pure forms, pharmaceutical formulations and human plasma. The method was based on condensation reaction of cited drugs with ninhydrin and phenylacetaldehyde in buffered medium (pH 6) resulting in formation of fluorescent products which exhibit excitation and emission maxima at 395 and 470nm, respectively. The different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The calibration plots were constructed with good correlation coefficients (0.9993 for tobramycin and 0.9996 for both neomycin and amikacin). The proposed method was successfully applied for the analysis of cited drugs in dosage forms with high accuracy (98.33-101.7)±(0.80-1.26)%. The results show an excellent agreement with the reference method, indicating no significant difference in accuracy and precision. Due to its high sensitivity, the proposed method was applied successfully for determination of amikacin in real human plasma.

Resonance Rayleigh scattering and resonance non-linear scattering method for the determination of aminoglycoside antibiotics with water solubility CdS quantum dots as probe.

In pH 6.6 Britton-Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (DeltaI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3 sigma) were 1.7 ng mL(-1) (NEO) and 4.4 ng mL(-1) (STP) by RRS method, were 5.2 ng mL(-1) (NEO) and 20.9 ng mL(-1) (STP) by SOS method and were 4.4 ng mL(-1) (NEO) and 25.7 ng mL(-1) (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.

Determination of neomycin and bacitracin in human or rabbit serum by HPLC-MS/MS.

The method for the simultaneous determination of neomycin and bacitracin in human or rabbit serum was developed by using ion pairing reversed phase chromatography and tandem mass spectrometry (MS/MS) detection with electrospray (ESI) in positive mode. Both substances elute under these conditions at the same time and also kanamycin as internal standard elutes almost at the same time. The sample preparation was simple-only using 0.1 mL serum by protein precipitation with acetonitrile. Neomycin and bacitracin were detected as two-fold charged ions as well as the internal standard. The calibration range of these quite difficult detectable substances was 0.2-50 microg/mL of serum. The method was validated for both human or rabbit serum. The inter batch precision of quality control samples in human serum for neomycin ranged from 4.46% to 8.99% and for bacitracin from 6.85% to 11.17%. The inter batch accuracy for neomycin ranged from 98.7% to 100.7% and for bacitracin from 99.2% to 103.0%. At lower limit of quantitation (LLOQ) level of 0.2 microg/mL inter batch precision in human serum for neomycin was 12.05% and for bacitracin 11.91%, whereas accuracies were 99.9% for neomycin and 102.7% for bacitracin. Bench top stability in human or rabbit serum was given over three freeze thaw cycles and 4h at room temperature. The method can be considered to be specific and recoveries for sample preparation were high.

Development of ELISA and immunochromatographic assay for the detection of neomycin.

BACKGROUND: Reliable analytical methods are required to monitor neomycin residue levels in the livestock products. In particular, a more simple and rapid detection method is required in the veterinary fields. METHODS: Competitive direct ELISA and immunochromatographic assay were developed using monoclonal antibody to detect neomycin in the animal plasma and milk. RESULTS: No cross-reactivity of the antibody was observed with other aminoglycosides based on competitive direct ELISA methods, indicating that the antibody is highly specific for neomycin. Based on the standard curves, the detection limits were determined to be 6.85 ng/ml in PBS, 3.61 ng/ml in plasma, and 2.73 ng/ml in milk, respectively. Recoveries of neomycin from spiked plasma and milk at levels of 50-200 ng/ml ranged from 87% to 108%. Concentration of intramuscularly injected neomycin was successfully monitored in the rabbit plasma through competitive direct ELISA. Immunochromatographic method was also developed using colloidal gold-conjugated monoclonal antibody. Through this method, the detection limits were estimated to be about 10 ng/ml of neomycin in PBS, plasma, and milk. CONCLUSIONS: Immunochromatographic assay developed in this study is suitable for the simple screening of neomycin residues in the veterinary field. Observed positives can be confirmed using a more sensitive laboratory method such as competitive direct ELISA.

Determination of neomycin by LC-tandem mass spectrometry using hydrophilic interaction chromatography.

A specific, and automated method was developed to quantitate neomycin in human serum. Samples were prepared with an automated solid phase extraction (SPE). The hydrophilic interaction chromatography (HILIC) was used for additional sample cleanup and baseline separation. The analyte neomycin was detected with electrospray ionisation tandem mass spectrometry (ESI-MS-MS). Using a volume of 500 microl biological sample the lower limit of quantification was 100 ng/ml. The described HILIC-MS-MS method is suitable for clinical and pharmcokinetical investigations of neomycin.

Sensitive high-performance liquid chromatographic assay for aminoglycosides in biological matrices enables the direct estimation of bacterial drug uptake.

Following the development of a sensitive high-performance liquid chromatographic (HPLC) assay for gentamicin in biological matrices, the utility of this assay for the determination of other clinically important aminoglycosides (neomycin, netilmicin and sisomicin) in bacterial culture media or plasma is demonstrated. The high sensitivity of the assay enables direct measurement of the aminoglycoside content of bacterial cells cultured in the presence of unlabelled drug.

Prospective evaluation of neomycin serum concentrations after direct corpora cavernosa irrigation during penile prosthesis placement.

OBJECTIVES: To determine if toxic serum levels of neomycin are generated after direct corpora cavernosa irrigation during penile prosthesis placement. METHODS: We have used an infection prophylaxis technique that involves directly irrigating the corpora cavernosa tissue (through the corporotomy) with 0.5% neomycin solution. Serum neomycin concentrations were measured at 1 hour and 4 hours after irrigation in 13 patients undergoing penile prosthesis placement. A subset of patients who had preimplant and postimplant serum creatinine concentrations was evaluated for changes in renal function. RESULTS: The mean 1-hour postirrigation serum neomycin level was 1.2 micrograms/mL and the mean 4-hour postirrigation level was 1.2 micrograms/mL. These serum neomycin concentrations are lower than those thought to be necessary to produce nephrotoxicity or ototoxicity. Renal function was not significantly affected by the neomycin irrigation. CONCLUSIONS: Although aminoglycosides are ototoxic and neomycin has the highest nephrotoxic potential of the aminoglycosides, we conclude that direct irrigation of the corpora cavernosa with 0.5% neomycin solution does not produce significant systemic exposure to result in nephrotoxicity or ototoxicity. One-time prophylactic neomycin irrigation remains an effective, safe, and economic adjunct to penile prosthesis placement.

Determination of neomycin in plasma and urine by high-performance liquid chromatography. Application to a preliminary pharmacokinetic study.

A reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the determination of neomycin in plasma and urine. The plasma was deproteinated with trichloroacetic acid and centrifuged. The supernatant was mixed with ion-pair concentrate and centrifuged again. The resultant supernatant was analyzed by HPLC. Urine was centrifuged to remove debris, if any, mixed with ion-pair concentrate and analyzed directly by HPLC. The HPLC conditions consisted of an ion-pairing mobile phase, a reversed-phase column, post-column derivatization with o-phthalaldehyde (OPA) reagent and fluorescence detection. The overall average recovery of neomycin was 97 and 113% from plasma spiked at 0.25-1.0 micrograms/ml, using standard curves prepared in plasma extract and in water, respectively, and 94% for urine spiked at 1-10 micrograms/ml using a standard curve prepared in water. The method was used to detect neomycin in plasma and urine obtained from animals injected intramuscularly with neomycin. Various pharmacokinetic parameters of neomycin were also determined from its profile of plasma concentration versus time.

Hearing loss following the application of topical neomycin.

Profound, irreversible ototoxicity has been reported following oral and topical neomycin therapy. Preexisting renal disease is a known risk factor for this adverse effect. In spite of the potential hazards of this drug, it continues to be used widely both orally and topically. This is a report of a severe, permanent hearing deficit that occurred in a patient with chronic renal failure. The patient, who had developed decubitus ulcers, was treated for three weeks with topical 1% neomycin solution applied in gauze-soaked bandages. Regular hemodialysis failed to prevent this adverse effect. Caution should be exercised in selecting patients to receive prolonged neomycin therapy.

Absorption of neomycin from the equine uterus: effect of bacterial and chemical endometritis.

Plasma concentrations of neomycin were measured after intrauterine infusion of 3.3 mg/kg neomycin sulphate. Mares infected two hours previously with an intra-uterine infusion of beta-haemolytic streptococci absorbed approximately 12 per cent of the neomycin in both the oestrous and the luteal phases of the cycle. Normal mares in oestrus absorbed 6 per cent of the neomycin infused and luteal mares absorbed 56 per cent. In infected mares the peak plasma concentrations occurred two hours after neomycin infusion, earlier than in healthy mares. Cervical flushings after neomycin infusion in infected luteal mares revealed an increased reflux of neomycin when compared with healthy mares. Prior infusion of 30 ml of 10 per cent Lugol's iodine into the uterus resulted in 31 per cent of neomycin being absorbed by oestrous mares and 64 per cent by mares in the luteal phase. Peak plasma concentrations occurred 30 minutes after infusion in both phases. In the luteal phase the mares' absorption of neomycin may have been maximal.

Oral neomycin sulfate and erythromycin base before colon surgery: a comparison of serum and tissue concentrations.

It is accepted that the use of oral neomycin sulfate and erythromycin base before colon surgery results in decreased numbers of intestinal bacteria. Intraluminal levels of these agents are reported to be very high, but systemic availability is still debated. The systemic levels were studied in 8 patients undergoing colon surgery. Each patient received neomycin sulfate and erythromycin base, 1 g each, 19, 18 and 9 hours preoperatively. Twelve samples from serum, one from wound muscle and one from the intestinal wall were obtained from each patient in the 26 hours after the initial dose. Considerable variation was observed among levels. The following means were calculated: peak serum levels were 3.4 and 0.59 micrograms/ml, muscle levels were 1.68 and 0.23 micrograms/g and intestinal wall levels were 6.4 and 12.9 micrograms/g for erythromycin and neomycin respectively. Observed times to peak levels were 19 and 12 hours after the initial dose for erythromycin and neomycin respectively. The detectable systemic concentrations that result when these agents are given orally for bowel preparation before colon surgery may contribute to the drugs' efficacy.

Neomycin and plasma lipoproteins in type II hyperlipoproteinemia.

Neomycin, a nonabsorbable aminoglycoside antibiotic, has been shown to exert a hypocholesterolemic effect in man. In a 9-mo, double-blind, randomized, crossover, placebo-controlled clinical trial, the effect of neomycin, 2 gm/day, on plasma lipoproteins, as well as its safety, was described in 20 subjects with type II hyperlipoproteinemia. A 15% (50 mg%) decline in plasma cholesterol concentration was observed with neomycin. Most of this effect resulted from a 41 mg% (16%) decrease in low-density lipoprotein cholesterol concentration. No significant or consistent effect on the concentration of high-density lipoprotein cholesterol was observed. Monthly audiologic and renal evaluation disclosed no oto- or nephrotoxicity. Neomycin treatment in patients with type II hyperlipoproteinemia is an inexpensive and effective means of lowering the concentration of low-density lipoproteins and is free of significant side effects over a 3-mo period.

[Use of neomycin-bacitracin irrigating solution with intraoperative autotransfusions during orthopedic operations]. / Anwendung von Neomycin-Bacitracin-Spüllösung bei intraoperativer Autotransfusion während orthopädischer Operationen.

Although there is doubt about the importance of rinsing the operative field with a solution containing locally acting antibiotics, it is frequently done. In this paper we tried to answer the question, wether intraoperative autotransfusion (IAT) with the Haemonetics Cell Saver is contraindicated during rinsing the operative area with locally acting antibiotics or vice versa. The measured serum concentrations for neomycin and bacitracin (Nebacetin) were extremely low. Therefore IAT is recommended with a system separating and washing the autologous red blood cells even under circumstances of rinsing the operative field with a solution containing locally acting antibiotics.

[Local infection prophylaxis with nebacetin in neurosurgical procedures]. / Zur lokalen Infektionsprophylaxe mit Nebacetin bei neurochirurgischen Eingriffen.

With the application of neomycinsulfat (Nebacetin) during neurosurgical operations the authors observed an infection rate below 1%. The form of application is intracerebral, epidural or intramuscular depending on the operation itself, wound infections and serum concentrations of neomycinsulfat are reported separately.

[Antibiotic concentration in postoperative wound secretions and in serum of patients after implantation of hip endoprostheses having used neomycin-bacitracin loaded bone cement (author's transl)]. / Antibiotikakonzentrationen im Wundsekret und im Serum nach Implantation von Hüftendoprothesen unter Verwendung eines Knochenzements mit Neomycin-Bacitracin-Beimischung.

Antibiotic concentrations in postoperative wound secretions and in serum give some indication of the local and general effects of an antibiotic additive to bone cement. Ten patients received hip endoprostheses using a prepacked mixture of the bone cement Sulfix 6 with neomycin + bacitracin (Sulfix 6 A). After operation secretions from Redon drains were collected over the next 48 hours as well as venous blood over 14 days in order to measure neomycin and bacitracin levels. Neomycin was found in sera of some patients up to the eighth postoperative day, whereby concentrations did not exceed 0.75 mcg/ml. Bacitracin was not detected in any serum samples. In secretions from Redon drains neomycin as well as bacitracin reached effective levels during the first 48 hours. The results indicate that the addition of neomycin and bacitracin to the bone cement Sulfix 6 for local antibiotic prophylaxis is justified since effective antibiotic concentrations are thereby obtained in the wound without the danger of general toxicity arising when neomycin and bacitracin are administered by the usual method of topical application.

Neomycin absorption following Clagett procedure for postpneumonectomy empyema.

Following a Clagett stage II procedure, significant amounts of neomycin are absorbed when concentrations of 0.25% neomycin (8.9 micrograms milliliter) are used. If higher concentrations are employed, the neomycin can achieve toxic levels (40 micrograms per milliliter), with associated renal toxicity and respiratory suppression. The peel of the empyema cavity does not prevent absorption of drugs. Therefore, when drugs are inserted into an empyema cavity, due care must be exerted to prevent drug toxicity.

[Neomycin resorption from the normal and inflammatorily altered peritoneum]. / Zur Neomycin-Resorption aus dem gesunden und entzündlich veränderten Peritoneum.

The clinical problem of the resorption of Neomycin from the normal and inflammatory altered peritoneal cavity was studied experimentally in the guinea pig. In a total of 197 guinea pigs the pharmacokinetics of Neomycin in serum and perilymph after injection subcutaneously or in normal and inflammatorily altered peritoneal cavity of the guinea pig were determined. No statistically significant difference between the pharmacokinetics of Neomycin in serum and perilymph of the different series could be found. The possible clinical relevance of the results is discussed.

Neomycin ototoxicity.

A case of oral neomycin ototoxicity is presented, followed by a summary of known cases in the English literature. While it is known that neomycin is concentrated in the inner ear fluids, at the present time the biochemical basis of its ototoxic effect has not been definitively elucidated. High frequency audiometry can aid in the early detection of the onset of neomycin-induced deafness. Dialysis has a limited but useful role in preventing neomycin ototoxicity.

Effects of oral neomycin and kanamycin in chronic uremic patients: I. Urea metabolism.

The fate of portal ammonia derived from intestinal urea degradation was examined in 15 experiments in patients with chronic renal failure. The kinetics of labelled urea metabolism were studied before and again during the administration of oral neomycin or kanamycin. Detectable absorption of both drugs generally occurred, but urea clearance and estimated glomerular filtration rate did not significantly change during antibiotic administration. In seven experiments a significant fall in urea degradation (65% to 95%) occurred during antibiotic administration. Analysis of the effect of antibiotics was confined to these seven experiments. In the control periods, there were no differences in urea metabolism or renal function between these patients and those in whom urea degradation was not suppressed. If ammonia derived from urea degradation is converted back to urea in the liver, then suppression of degradation would lead to an equal decrease in urea production, and the difference between production and degradation ("appearance") would remain constant. However, if urea-derived ammonia is used for protein synthesis, suppression of degradation would permit the formerly degraded urea to appear in urine and body fluids and thus to increase urea appearance. In these seven experiments, we found no change in urea appearance during antibiotic administration. We conclude that portal ammonia is reincorporated into urea in chronic renal failure and is not utilized significantly for protein synthesis.