There are no drug interactions between nitrofurantoin (Macrobid) and fluconazole (Diflucan). This combination makes sense to use in urinary infections that are thought to be of bacterial and/or fungal origin.


Information About Nitrofurantoin

Nitrofurantoin is an antibiotic that is only approved for treatment of urinary tract infections. This is because nitrofurantoin is quickly and extensively concentrated in the urine. It has been approved by the FDA since 1953.

The half-life of nitrofurantoin is only about 20 minutes and typically reaches peak urinary concentrations in about 30 minutes.

Because nitrofurantoin is excreted in the urine, the manufacturer does not recommend use in patients with impaired renal function (creatinine clearance below 60 mL/min). In addition, nitrofurantoin is listed by the Beers Criteria as a medication to avoid in elderly adults with a creatinine clearance less than 30 mL/minute.


Information About Fluconazole

Fluconazole is an antifungal that can be used for a wide range of fungal infections. It has been approved by the FDA since January of 1990. In 1994, the FDA approved a single dose for the treatment of uncomplicated vulvovaginal candidiasis (yeast infection).

The half-life for Diflucan usually ranges between 20 and 50 hours (approximately 30 hours in most patients). Fluconazole is well absorbed via the oral route with a bioavailability of 90%. Peak concentration takes place in 1 to 2 hours with both oral and intravenous routes.

Fluconazole has been rarely associated with QT prolongation. This would be of concern in patients with proarrhythmic conditions or when taking other medications that prolong the QT interval. Nitrofurantoin has not been associated with an increased QT.