1989 Volume 4 Issue 6 Pages 793-804
Plasma levels, distribution, excretion and metabolism of [14C] zonisamide was studied in rats of different age (1-, 14-, 28 and 49-days old).
After oral administration of 20mg/kg to 1-and 14-days old rats, the elevation of plasma levels was slightly delayed in comparison with rats of other ages. However, maximal plasma levels were similar to each other (13-18μg eq. /ml) in all ages studied. Disappearance half life of plasma radioactivity in 1-day old rats was 133 hr, which was markedly longer than that in elder rats(6-12 hr). Zonisamide concentration in erythrocytes was lower in younger rats. This was found to be correlated with the activity of erythrocyte carbonic anhydrase, a component for zonisamide binding. Radiometric and autoradiographic studies revealed that distribution pattern of radioactivity in tissues was similar to each other in all ages studied. Radioactivity was mostly excreted in urine of 14-, 28 and 49-day old animals. Composition of urinary metabolites was qualitatively similar to each other in 14-, 28-and 49-day old rats but from quantitative point of view was different.
