Antacids containing magnesium trisilicate, when administered concomitantly with nitrofurantoin, reduce
both the rate and extent of absorption. The mechanism for this interaction probably is adsorption of nitrofurantoin
onto the surface of magnesium trisilicate.
Uricosuric drugs, such as probenecid and sulfinpyrazone, can inhibit renal tubular secretion of
nitrofurantoin. The resulting increase in nitrofurantoin serum levels may increase toxicity, and the decreased
urinary levels could lessen its efficacy as a urinary tract antibacterial.
Drug/Laboratory Test Interactions
As a result of the presence of nitrofurantoin, a false-positive reaction for glucose in the urine may
occur. This has been observed with Benedictís and Fehlingís solutions but not with the glucose