GENTAMICIN DETERMINATION IN BIOLOGICAL-FLUIDS BY HPLC, USING TOBRAMYCIN AS INTERNAL STANDARD

An improved procedure to quantify gentamicin in biological fluids is presented. The antibiotic is isolated from plasma and urine by using a silica column, and measured by reversed-phase chromatography. Pre-column derivatization with ophthalaldehyde to form fluorescent products for detection is used. The method can accurately measure 0.3 mg of gentamicin per liter, and standard curves showed a linear response in plasma and urine at concentrations ranging from 0 to 10 mg/liter. The different processes described in the literature for aminoglycoside isolation are discussed and evaluated with reference to the present results. Moreover, the use of several antibiotics as internal standards is described. This procedure is useful to quantify plasma and urine concentrations of gentamicin administered free or encapsulated in liposomes.