Drugs which reduce gastric acidity may result in a lower bioavailability of Cefuroxime compared with that of the fasting state and tend to cancel the effect of enhanced post-prandial absorption. In common with other antibiotics, Cefuroxime may affect the gut flora, leading to lower estrogen reabsorption and reduced efficacy of combined oral contraceptives. As a false negative result may occur in the ferricyanide test, it is recommended that either the glucose oxidase or hexokinase methods are used to determine blood/plasma glucose levels in patients receiving Cefuroxime. This antibiotic does not interfere in the alkaline picrate assay for creatinine. Probenecid reduces the renal clearance of Cefuroxime.