Open AccessEffects of Radiopharmaceuticals on Radioenzymatic Assays of Aminoglycoside Antibiotics: Interference by Gallium-67 and Its Elimination
Author(s) -
Ishan Bhattacharya,
Robert Seligsohn,
Stephen A. Lerner
Publication year - 1978
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.14.3.448
Subject(s) - gentamicin , aminoglycoside , diisopropyl ether , chemistry , amikacin , tobramycin , chromatography , extraction (chemistry) , antibiotics , radiochemistry , microbiology and biotechnology , ether , biochemistry , biology , organic chemistry
Radionuclides currently used in clinical medicine were evaluated for their possible interference with radioenzymatic assays of aminoglycoside antibiotics. Of the radiopharmaceuticals tested, only67 Ga citrate interfered with the radioenzymatic assay of gentamicin. Radioenzymatic assay of serum samples obtained from patients receiving67 Ga yielded gentamicin concentrations falsely elevated by more than 1 μg/ml for approximately 1 week after67 Ga administration. A procedure was developed to eliminate67 Ga interference with radioenzymatic assays of aminoglycoside antibiotics. After67 Ga citrate was spotted onto phosphocellulose filter disks, the filters were immersed in 7.2 N HCl, and radioactivity was removed by successive extractions of the acid phase with diisopropyl ether. After three extractions, less than 0.1% of the original radioactivity remained. Similar extraction of disks containing14 C-adenylylated gentamicin or tobramycin or14 C-acetylated amikacin had no effect on14 C radioactivity. The concentrations of aminoglycosides in serum standards supplemented with67 Ga citrate were determined accurately by radioenzymatic assays followed by extraction with diisopropyl ether. Concentrations of gentamicin in six serum samples from patients injected with67 Ga during gentamicin therapy, as determined by radioenzymatic assay and extraction, were within 9% of the results obtained by reassay of the same samples after the decay of67 Ga.