Urinary excretion reflects lung deposition of aminoglycoside aerosols in cystic fibrosis

Using nebulization to deliver aminoglycosides may be of benefit in cystic f ibrosis (CF) patients colonized by Pseudomonas aeruginosa. However, one pro blem with this route is the absence of clinical parameters allowing estimat ion of the mass of drug deposited in the lungs (MDL). The aim of this study was to assess whether aminoglycoside excretion in the urine reflects the M DL. Fourteen studies were performed in seven CF patients. Amikacin was mixed wi th albumin labelled with Tc-99m and nebulized with an ultrasonic nebulizer. The MDL was determined by the mass-balance technique. Urine was collected during the 24 h following inhalation and was assayed for amikacin by fluore scence polorization immunoassay (FPIA). The mean SEM MDL was 14.0 +/-2.2% o f the nebulizer charge. The mean SEM amount of amikacin excreted in the urine was 20.9 +/-4.5 mg an d correlated with the MDL (r=0.93; p=0.0001). There was, however, wide inte rsubject variability in both deposition and excretion in the urine. Monitoring excretion of aminoglycosides in the urine allows noninvasive est imation of the mass of drug deposited in the lung in cystic fibrosis patien ts, which might be useful to assess the dose-response relationship in group s of patients, but intersubject variability prevents its use for individual follow-up.