Radioimmunoassay of Iodinated Tobramycin

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An aminoglycoside antibiotic and carbenicillin or ticarcillin are widely used in the treatment of patients with gram-negative bacillus infections. This study evaluated the effect of time upon in vitro interaction between mixtures of four aminoglycosides at two concentrations with carbenicillin or ticarcillin at four concentrations. By linear regression analysis, the inactivation of each aminoglycoside was shown to be directly proportional to the concentration of carbenicillin ( P < 0.001). Inactivation was significantly ( P < 0.01) greater for gentamicin and tobramycin than for amikacin or netilmicin at all carbenicillin concentrations. At carbenicillin concentrations of 300 and 600 μg/ml, significantly ( P < 0.005) less inactivation of amikacin occurred when compared to netilmicin. Ticarcillin produced a significant ( P < 0.025) inactivation of gentamicin and tobramycin, with inactivation being directly proportional to ticarcillin concentration. No inactivation of amikacin or netilmicin activity occurred unless the ticarcillin concentration was 600 μg/ml. No significant change in aminoglycoside activity occurred when stored with ticarcillin or carbenicillin at concentrations ranging from 100 to 600 μg/ml at −70°C for 56 days. When an aminoglycoside and carbenicillin or ticarcillin are indicated in patients with renal failure, this study supports the use of ticarcillin with either amikacin or netilmicin.

Section: Pickering and Gearhartmentioning

confidence: 99%

mentioning

confidence: 99%

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Effect of Time and Concentration Upon Interaction Between Gentamicin, Tobramycin, Netilmicin, or Amikacin and Carbenicillin or Ticarcillin

Pickering

Gearhart

1979

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“…Therapeutic treatment requires frequent monitoring of gentamicin in the blood (8), the assays commonly used being the microbiological disk test (10) and a radioimmunoassay (RIA) (2,3). This assay has great sensitivity and a high degree of specificity.…”

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confidence: 99%

Radioimmunoassay of gentamicin in Micromonospora medium extracts

Rosner¹,

Aviv²

1980

“…To insure adequate patient treatment, frequent monitoring of aminoglycoside serum drug levels has been advocated to avoid either inadequate or excessively high serum concentrations of the antibiotic (3,9,11,14). Numerous methods have been described for assaying tobramycin serum concentrations including: bioassay (8,10,12), enzymatic assays (13), gas-liquid chromatography (6, 7), high-pressure liquid chromatography (1), and radioimmunoassay (RIA) (2).…”

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confidence: 99%

Comparison of radioimmunoassay with a new immunofluorescent method (FIAX) for measuring tobramycin in serum

Bruckner¹,

Hindler²,

Martin³

et al. 1982

A new immunofluorescent method (FIAX) was compared with a radioimmunoassay procedure for the determination of tobramycin serum concentrations. When assaying three tobramycin control sera repeatedly, within-run and run-to-run variations by the FIAX method were all within acceptable limits, and no statistically significant differences were found. Results (3,9,11,14). Numerous methods have been described for assaying tobramycin serum concentrations including: bioassay (8, 10, 12), enzymatic assays (13), gas-liquid chromatography (6, 7), high-pressure liquid chromatography (1), and radioimmunoassay (RIA) (2).In this study, the FIAX immunofluorescent assay method was compared with RIA to determine the following: (i) within-run precision; (ii) run-to-run reproducibility; (iii) accuracy of determinations by comparison with expected values; and (iv) the reliability of the FIAX method in determining tobramycin levels in patient sera. MATERIALS AND METHODSThis study employed 155 selected serum samples from patients who had been under treatment with tobramycin. Specimens that could not be assayed on the day they were obtained were frozen and stored at -20°C until tested.RIA. Tobramycin RIA kits were obtained from Diagnostic Products Corp., Los Angeles, Calif. All samples were assayed according to their recommended protocol.FIAX. All reagents used for the FIAX assay procedure were supplied by International Diagnostic Technology, Santa Clara, Calif.The solid-phase immunofluorescence method primarily involves competition between a fluoresceinlabeled and an unlabeled antigen for a fixed amount of antibody immobilized on a reactive surface. In this case, specific anti-tobramycin antibody was immobilized on a defined polymeric surface such as that which is present on the StiQ sampler. This sampler was immersed sequentially into a mixture of fluorescein-labeled tobramycin and a sample (standards, controls, or unknown) containing unlabeled tobramycin. Thus, the amount of fluorescein-labeled tobramycin that attaches to the specific anti-tobramycin antibody is inversely proportional to the concentration of unlabeled tobramycin in the sample.The following procedure outlines the assay protocol used in this study: 700 gul of fluorescein-labeled tobramycin was dispensed into 12-by 75-mm glass tubes to which 10 ,ul of sample (standard, control, or unknown) was added; each sample was tested in duplicate. All tubes were shaken briefly by hand. StiQ samplers were placed into these tubes and then mixed on a mechanical shaker for 25 min at room temperature. The tubes and StiQ samplers were removed from the shaker and allowed to equilibrate for an additional 5 min before reading. Fluorescence is measured on a fluorometer set at 995 nm (excitation) and 530 nm (emission). The degree of fluorescence was expressed in fluorescence signal units. The fluorometer was adjusted to read 190 fluorescence signal units with a reference solution containing 1 ,ug of tobramycin per ml.A standard curve was constructed with tobramycin standards (included in t...