The early limb deformity caused by acetazolamide.

Histologic sections were made of the forelimbs of day 10 to 12.5 embryos removed 3, 16, 30, 36, 42, 45, 63 and 75 hours after the intraperitoneal injection of acetazolamide into C57Bl/6J pregnant females. A postaxial deformity was first visible in the right forelimb of day 10.9 embryos 36 hours after the second dose of acetazolamide 1,000 mg/kg on day 9 of gestation. The deformity was a postaxial deficiency of mesenchyme tissue without any evidence of cell necrosis. The deformity was present before aggregation of mesenchyme cells occurs as the first step in chrondrogenesis. The pattern of cell orientation in the adjacent mesenchyme aggregate of a deformed day 12.5 forelimb was normal. This means that the primary effect of acetazolamide is not on the formation of precartilage aggregates in the postaxial region, but involves other aspects of early limb development.