Radioimmunoassay for serum tobramycin levels using 125I-labeled tobramycin

A radioimmunoassay is described for the measurement of tobramycin in serum or plasma. The technique has advantages over other assay techniques with regard to precision, specificity, sensitivity and rapidity. The radioimmunoassay uses a tracer labelled with 125Iodine. The iodination technique is simple and gives tracer in high yield, at high specific activity and with complete immunological identity to unlabelled tobramycin. There is a significant correlation between the results obtained by this radioimmunoassay and by the disc-plate assay. Such knowledge of serum levels of tobramycin assists the clinician in regulating drug dosage to obtain an optimum therapeutic effect, and yet avoids toxic serum levels.