Effect of mixing on the bioavailability of nitrofurantoin capsules.

The effect of blending time on the "in vivo" absorption of powder mixtures of similar composition, containing nitrofurantoin (NF), both in crystalline (10-50 u diameter) and macrocrystalline (70-80 u diameter) forms, was studied. The blending operations were performed using a Twin-Shell Blender (V-Type). The ingredients were blended long enough to obtain homogeneity, and this point was considered as "zero time". The mixing was continued and a intensifier bar was placed inside the blender. Samples were collected at 0; 30 and 45 minutes of blending and hard gelatin capsules were filled with these samples. A bioavailability study was performed in six healthy male volunteers. The experiments were conducted in a crossover fashion and each volunteer took one capsule of each time of blending of both microcrystalline and macrocrystalline nitrofurantoin. Urine samples were collected after the administration of the drug, and assayed by a spectro-fluorometric method. The total nitrofurantoin (NF) amount excreted in urine showed statistically significant differences at different times of blending only when capsules containing microcrystalline drug were administered.