Nitrofurantoin 100 mg (SR) Film Coated · Tablets

Nitrofurantoin is an antibacterial drug [see Microbiology (12.4)].

Absorption — Orally administered nitrofurantoin oral suspension is readily absorbed. Blood concentrations at therapeutic dosage are usually low.

Effect of Food — The presence of food or agents delaying gastric emptying can increase the bioavailability of nitrofurantoin oral suspension.

Distribution — Nitrofurantoin is highly soluble in urine. Nitrofurantoin lacks the broader tissue distribution of other therapeutic agents approved for urinary tract infections.

Excretion — Nitrofurantoin is rapidly excreted in urine, to which it may impart a brown color.

Following a dose regimen of 100 mg four times a day for 7 days, average urinary drug recoveries (0 hour to 24 hours) on Day 1 and Day 7 were 42.7% and 43.6%.

Specific Populations — The pharmacokinetics of nitrofurantoin oral suspension are unknown for the geriatric patients, pediatric patients, patients with hepatic impairment, or pregnant women. Differences between male and female patients, and racial or ethnic groups are unknown.

Patients with Renal Impairment — The reported urinary recoveries of nitrofurantoin after a single 100 mg oral dose and 100 mg four times a day in patients with varying renal function showed approximate linear relationship between the amount of nitrofurantoin recovered and creatinine clearance.

Antacids such as magnesium trisilicate — In a cross-over study, the in vivo absorption characteristics of nitrofurantoin and nitrofurantoin-magnesium trisilicate combination were evaluated in 6 healthy males. The administration of 5 g magnesium trisilicate with 100 mg nitrofurantoin reduced the rate and extent of nitrofurantoin excretion reflecting decrease in both rate and extent of its absorption [see Drug Interaction (7.1)].

Propantheline — In a crossover study, the in vivo absorption characteristics of nitrofurantoin and propantheline (an anticholinergic agent) combination were evaluated in six subjects. Administration of 30 mg of propantheline 45 min prior to nitrofurantoin 100 mg administration resulted in a statistically significant increase in nitrofurantoin excretion, however, the clinical significance of this effect is unknown.