Routine methods in toxicology and therapeutic drug monitoring by high performance liquid chromatography: III. A rapid microscale method for determination of furosemide in plasma and urine.

A highly specific, sensitive, and rapid microscale method is described for determining furosemide levels in plasma and urine. Monitoring furosemide levels has been recommended in patients with impaired renal function and in premature infants since furosemide has been known to cause ototoxicity. The method described here is simple, easy to run, takes only 7 min per sample, and can be set up for routine monitoring of furosemide by clinical laboratories. The method uses ion-pairing high performance liquid chromatography and detection of furosemide by fluorescence, which gives excellent separation and high sensitivity with minimal sample preparation. The method requires only 25 microliters of plasma or urine and, thus, is suitable for use in newborn intensive care units.