In vitro and in vivo evaluation of seven 50 mg and 100 mg nitrofurantoin tablets

Abstract

Four 50 mg and three 100 mg marketed nitrofurantoin tablets were studied in 14 healthy male subjects. Urine was collected 1, 2, 3, 4, 6, 8, 12, and 23 h after each dose, and nitrofurantoin was assayed by HPLC. The in vitro dissolution of the tablets was determined using USP Apparatus 1 and 2, with 0.1 N hydrochloric acid and pH 7.2 buffer as the dissolution fluids. One of the 50 mg tablets was more rapidly and completely absorbed than the other six products. The incidence of side-effects for this product was as low or lower than the other products. It was determined that the use of the USP Apparatus 1, at 100 rev min-1, with sampling of the pH 7.2 fluid at 30 min, provided for the best overall relationship between the urinary excretion and in vitro dissolution.

Reduced Bioavailability of Moisture‐Exposed Carbamazepine Resulting in Status Epilepticus

“…In vitro studies demonstrated that increasing the moisture content of CBZ tablets by exposure to high humidity resulted in a lowering of the dissolution profile (Wang et al, 1990). Human studies show a strong relation between in vitro dissolution and in vivo bioavailability of CBZ (Wang et al, 1990) and other drugs (Skelly, 1976;Meyer et al, 1989). Therefore, it is not unexpected that tablets contaminated by direct exposure to water would dissolve poorly in vivo, resulting in reduced bioavailability and, as a consequence, low CBZ serum levels.…”