In vitro effect of penicillins and aminoglycosides on commonly used tests for glycosuria

The effect of penicillins (ampicillin, carbenicillin, penicillin G, and penicilloic acid) and aminoglycosides (amikacin, gentamicin, streptomycin, and tobramycin) on the accuracy of Clinitest, Diastix, and TesTape determinations of glycosuria was studied. Solutions of each of the drugs were prepared in urine in a range of clinically obtainable drug concentrations. In addition, urine solutions were prepared that contained the same drug concentrations and sufficient glucose to give final concentrations of 0.5, 1, and 2%. All solutions were tested in triplicate using the five-drop Clinitest method, Diastix, and TesTape. Falsely elevated and falsely decreased Clinitest readings were obtained with the penicillins. These readings were influenced by the concentration of the penicillins and of glucose. The aminoglycosides had no effect of Clinitest determinations. Neither drug class interfered with Diastix or TesTape readings. The Clinitest-penicillin interaction is unpredictable. If Clinitest is used as a quantitative test for glycosuria in patients receiving penicillins, the results should be rechecked using a qualitative method such as the glucose oxidase tests, Diastix or TesTape. All three tests can be used to test for glycosuria in patients receiving aminoglycosides.