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November 11, 1974

Interference With Urinary Glucose Determination by Cephalothin

Author Affiliations

Stanford Medical Center Palo Alto, Calif

JAMA. 1974;230(6):822-823. doi:10.1001/jama.1974.03240060012010

To the Editor.—  Cephalothin is one of the more frequently used antibiotics in clinical medicine today. In recent years, there have been reports indicating its interference in urine glucose determinations by the copper reduction method (Clinitest). Feldman et al1 reported in an in vitro study that cephalothin (5 mg/ml) reduced Clinitest tablets while not affecting glucose oxidase tests. No mention was made, however, to the specific color change. A previous study2 noted a confusing reaction for glucose in three cases during routine urine testing with Clinitest. In two of these patients (one being a diabetic), while they were receiving cephalothin, a resulting reaction was characterized by a confusing brown-black color. A third patient, also a diabetic and receiving cephalothin, showed a urine glucose reaction interpretable as possibly 2+ or 4 +.To clarify the significance of the cephalothin-Clinitest interaction, we used urine samples from 22 nondiabetic postsurgical patients. Patients