Homogeneous enzyme immunoassay for netilmicin

Adsorptive stripping voltammetric determination of netilmicin in the presence of formaldehyde

A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde has been proposed for the first time. In the presence of 3.0 x 10(-3) g ml(-1) formaldehyde, netilmicin exhibits a sensitive cathodic peak at -1.30 V (vs. the saturated calomel electrode, SCE) in a medium of Britton-Robinson buffer (pH 8.7) with a scan rate of 100 mV s(-1) after a preconcentration period of 120 s at -1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin concentration over the range 4.2 x 10(-9)-1.0 x 10(-7) g ml(-1). The achieved limits of detection and quantitation were 1.0 x 10(-10) and 3.3 x 10(-10) g ml(-1) netilmicin, respectively. It was deduced from the experiments that the amine-aldehyde condensation product formed between netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable formulations and spiked human urine and serum samples.

Comparison of a fluorescence polarization immunoassay of netilmicin in plasma, peritoneal dialysate, and urine with a high-performance liquid chromatographic method

The quantitative analysis of netilmicin in plasma, peritoneal dialysate, and urine using the fluorescence polarization immunoassay (FPIA) of the Abbott TDx system is compared with the modified high-performance liquid chromatography (HPLC) method of Peng et al., which was chosen as a reference. Using the least square method, we found that the results of the FPIA (y) correlated well with those obtained with HPLC (x). The three regression equations for the plasma, peritoneal dialysate, and urine samples, respectively, were y = 0.71x + 0.44 with r = 0.88 and n = 45; y = 0.94x + 1.22 with r = 0.93 and n = 95; and y = 0.92x + 0.70 with r = 0.93 and n = 61. The corresponding mean errors (FPIA-HPLC) with their 95% confidence intervals were -0.19 (-0.38 to -0.02), 0.69 (-0.42 to 1.81), and -0.13 (-1.13 to 0.87) microgram/ml. According to results of the Wilcoxon matched-pairs signed-ranks test, these errors did not represent a significant bias. The FPIA is thus suitable for analyzing netilmicin in the three biological fluids studied except when dialysate is contaminated with Amuchina. In this case, HPLC should be used.

Netilmicin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Netilmicin is a semisynthetic aminoglycoside derived from sisomicin. It is active against most Gram-negative and some Gram-positive bacteria, including many gentamicin-resistant strains. Netilmicin has proved to be effective in Gram-negative infections of the urinary tract, skin and skin structure, and lower respiratory tract, as well as in intra-abdominal infections, septicaemia and other miscellaneous infections. In some trials, the more easily implemented once daily administration of netilmicin has been as effective as multiple dosing regimens. However, further investigation is required to confirm that efficacy and safety are not compromised with once daily administration. Comparative studies have generally revealed similar clinical and bacteriological efficacies between netilmicin and gentamicin, amikacin or tobramycin. As with other aminoglycosides, the principal adverse effects of netilmicin are nephrotoxicity and ototoxicity. Although animal studies strongly suggest that these are less common with netilmicin than with related drugs, there appears to be no difference in their incidence in clinical use; in clinical trials the incidence of nephrotoxicity and ototoxicity has been low, with the symptoms in many cases being minor and reversible. Netilmicin is, therefore, an effective antibacterial drug for the parenteral treatment of severe infections, offering theoretical advantages in safety which may indicate its use for patients believed to be at risk of adverse effects.

High-performance liquid chromatographic determination of netilmicin in guinea-pig and human serum by fluorodinitrobenzene derivatization with spectrophotometric detection

A high-performance liquid chromatographic procedure for netilmicin determination in guinea-pig and human serum using pre-column derivatization with 1-fluoro-2,4-dinitrobenzene and UV detection is described. Linearity was established over the range 0.5-40 micrograms/ml using only 50 microliters of serum. Accuracy and precision were good, with a mean coefficient of variation less than 5% and a mean relative error less than 4%. This procedure correlates well with an enzyme multiplied immunoassay technique and has a sensitivity similar to those of published fluorescence derivatization methods.

Effect of cardiopulmonary bypass on vancomycin and netilmicin disposition

The effect of cardiopulmonary bypass (CPB) on the disposition of vancomycin (15 mg/kg) and of netilmicin (3 mg/kg) was studied in 10 adults. The concentration-time profile of the drug in serum and renal clearance were characterized pre-CPB, during CPB, and post-CPB. Vancomycin and netilmicin exhibited initial decreases in mean concentrations in serum of 4.0 mg/liter (16.8%) and 2.2 mg/liter (29.1%), respectively, upon initiation of CPB. Netilmicin concentrations in serum rebounded to a mean of 0.6 mg/liter (15.4%) within 90 min on CPB and then continuously decreased. Vancomycin concentrations in serum demonstrated a rebound increase of 2.3 mg/liter (23.5%) at the end of CPB when the aorta was unclamped. Mean renal clearance throughout CPB was decreased for vancomycin (58.4 to 43.4 ml/min per m2) and netilmicin (53.4 to 31.5 ml/min per m2). The rebound in vancomycin concentration in serum strongly correlated with the length of time between unclamping the aorta and coming off CPB (r = 0.94), as well as with the increase in temperature upon rewarming (r = 0.92).

Antimicrobial therapy of Pseudomonas pulmonary exacerbations in cystic fibrosis. A prospective evaluation of netilmicin plus azlocillin versus netilmicin plus ticarcillin

High-dose anti-Pseudomonas chemotherapy is mandatory in the treatment of acute pulmonary exacerbations in patients with advanced cystic fibrosis and Pseudomonas aeruginosa isolated from their sputum. However, neither the regimen itself nor its objective evaluation have been optimized yet. In a prospective controlled evaluation 42 such exacerbations were treated for two weeks with netilmicin combined by randomisation with either azlocillin or ticarcillin. Other aspects of therapy were constant. The two therapy groups were comparable in all aspects. Both regimens produced similar improvements in clinical, radiological, laboratory, bacteriological and pulmonary function measurements. Concentrations of sputum bacteria were significantly reduced; transient eradication was documented in 29% and correlated with antibiotic susceptibility of the initially isolated Pseudomonas strains. The highly dosed antibiotics were well tolerated and emergence of resistance was rarely observed. It is concluded that both antibiotic combinations are beneficial and safe in cystic fibrosis. Monitoring of such intensive hospital treatment must include multiple parameters.

Antibiotic monitoring in body fluids

Analytical procedures recently described for the quantitative determination of antibiotics in body fluids are reviewed. High-performance liquid chromatography (HPLC) and immunoassays appear as an alternative to current microbiological assays. HPLC has been applied to most antibiotics in clinical use and a major part of the review deals with this technique. Attention is given to sample pretreatment, characteristics of chromatography and detection, and limit of sensitivity. Non-isotopic immunoassays have been essentially applied to aminoglycosides and vancomycin and are also reviewed. Advantages and drawbacks of HPLC and immunoassays are presented.

Serum level monitoring of antibacterial drugs. A review

Serum concentration measurements of antibacterial agents are increasingly used to optimise drug dosage regimens. However, this approach is only justified for drugs with a low therapeutic index and poor predictability of serum concentrations, such as the aminoglycosides, chloramphenicol and vancomycin, whereas the penicillins and cephalosporins can safely be applied well above their minimum inhibitory concentrations. Wide interpatient variation in distribution and elimination are the main reasons for the unpredictability of aminoglycoside serum concentrations. It has been shown that in patients with normal creatinine clearance, the apparent elimination half-life of gentamicin varies from 0.4 to 7.6 hours. The pharmacokinetics of the aminoglycosides are most adequately described by a 3-compartment open model where the slow terminal half-life reflects elimination from the deep tissue compartment. The accumulation of the aminoglycosides in this compartment, which includes the kidneys and inner ear, is probably an important factor in their potential toxicity in these organs. Careful serum level monitoring may reduce, but cannot totally avoid, the risk of side effects. However, maintenance of effective drug levels appears to be at least an equally important goal of aminoglycoside serum level monitoring. Chloramphenicol is also a potentially toxic antibacterial agent. Its therapeutic range is usually considered to be 15 to 25 mg/L. The most important side effects are the 'grey baby syndrome' and bone marrow toxicity. Chloramphenicol is metabolised to several microbiologically inactive products. It also shows wide interpatient variability of its pharmacokinetics, especially in young children, and serum levels should therefore be followed in these patients. Vancomycin, a highly effective agent for staphylococcal and enterococcal infections, may also exhibit nephrotoxic and ototoxic side effects. A well-defined therapeutic range has not yet been established but in view of its minimum inhibitory concentrations it seems reasonable to maintain vancomycin serum concentrations between 15 and 50 mg/L. Since this drug is excreted unchanged in the urine, serum levels should particularly be monitored in patients with impaired renal function. The advances in routine therapeutic drug monitoring are directly related to rapid developments in technologies associated with the quantification of these agents. Microbiological plate diffusion assays are now often replaced by more specific immunoassays (radioimmunoassay, enzyme immunoassay, and fluorescence immunoassay) and chromatographic techniques.

Netilmicin sulfate: a comparative evaluation of antimicrobial activity, pharmacokinetics, adverse reactions and clinical efficacy

Netilmicin, the 1-N-ethyl derivative of sisomicin, is a new aminoglycoside antibiotic that was recently marketed in the United States. Its role in therapeutics is not yet established. The pharmacokinetic profile of netilmicin is very similar to that of gentamicin. Its antimicrobial spectrum and clinical efficacy is similar to that of gentamicin, tobramycin and amikacin. It is less active in vitro against Pseudomonas aeruginosa that gentamicin and tobramycin, but in clinical trials the efficacy of netilmicin against the organism has been similar to other aminoglycosides. Netilmicin is active against some gentamicin and tobramycin-resistant strains of gram-negative bacilli, particularly those harboring adenylating and phosphorylation enzymes. Most of these strains are sensitive to amikacin as well, and amikacin is also active against most netilmicin-resistant strains of these bacteria. Therefore, amikacin remains the aminoglycoside of choice against gentamicin tobramycin and netilmicin-resistant gram-negative bacilli. In comparison to other currently available aminoglycosides, a lower frequency of nephrotoxicity and ototoxicity has been observed in laboratory animals given netilmicin. This has not been unequivocally demonstrated in humans. The frequency of nephrotoxicity in humans has been similar to that of other aminoglycosides. The frequency of ototoxicity associated with netilmicin in humans has been low but not significantly less than in other aminoglycosides, except in one trial. If further studies document a significantly lower frequency of ototoxicity with netilmicin, it may become the aminoglycoside of choice for patients with significant risk factors for ototoxicity, such as advanced age, renal impairment, concomitant ototoxic drug therapy and prolonged aminoglycoside administration.