In vitro release and in vivo absorption of nitrofurantoin and nalidixic acid from ethylcellulose microcapsules.

Ethylcellulose was used as an efficient retarding material to prepare nitrofurantoin or nalidixic acid microcapsules. The dissolution rates of the different preparations have found to increase in alkaline rather than in acidic media. Considerable retardation in the rate and extent of release from 2:1, 1:1 and 1:2 drug-polymer ratios were observed as compared with those of the plain drugs. Absorption study in man proved that formulations containing 2:1 ratios have delayed urinary excretion rates by 2 h, however, the total cumulative amounts excreted from all samples remained almost constant. Man volunteers administered the 2:1 drug-polymer microcapsules did not suffer gastric irritation, usually produced after three consecutive d from taking the plain drugs. Experiments in male albino rats showed that the coated drugs did not produce gastric hemorrhage seen with the same doses of the uncoated ones.