Effect of Aging on the Bioavailability of Nitrdfurantoin Tablets Containing Carbopol 934

Abstract

This article reports a study of two nitrofurantoin tablet formulations differing in the percentage of Carbopol 934 used as binder. The tablets of both formulations each contained 50 mg of nitrofurantoin. Those of formulation A contained 0.625 mg of Carbopol 934, and those of formulation B 1.25 mg. When freshly prepared, tablets of both formulations were bioequivalent to capsules containing 50 mg of nitrofurantoin, but a year's storage at 40°C and 60% relative humidity caused a significant decrease in the bioavailability of nitrofurantoin from formulation B, whereas formulation A was still bioequivalent to capsules. USP XXI Ed. Method II successfully reflected the observed variations in bioavailability, but not Method I.