Toxicological evaluation of new calcium antagonists: 2-substituted 3-dimethylamino-5,6-methylenedioxyindenes

The 2-n-propyl (pr) and 2-n-butyl (bu) methylenedioxyindenes (MDIs) developed in our laboratories are intracellular calcium antagonists with coronary dilating and antiarrhythmic actions. Acute toxicity studies resulted, in mice, in an iv LD50 of 40 and 32 mg/kg for pr-MDI and bu-MDI, respectively, and an ip LD50 of 185 mg/kg for both MDIs. In rats, the ip LD50 was 175 and 240 mg/kg for pr-MDI and bu-MDI, respectively. An iv dose of 16 mg/kg decreased motor activity and prolonged barbiturate sleeping time in mice, but did not affect conditioned avoidance behavior or motor coordination tests. In sub-acute toxicity studies, rats received daily for 4 weeks 26.25 or 52.5 mg/kg ip of either MDIs, while mice received 23.13 or 46.25 mg/kg ip of either MDIs. No alterations were observed in serum alkaline phosphatase, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase, creatine phosphokinase, bilirubin, chloride, cholesterol, uric acid, prothrombin time, and bromsulphalein retention. Blood glucose was slightly lowered. Serum calcium was slightly lowered in male mice. The higher dose of pr-MDI elevated serum lactate dehydrogenase in rats. Both MDIs elevated serum isocitric dehydrogenase in male rats. Light microscopic examination of brain, kidney, liver, spleen, intestine, stomach, and myocardium showed no anomalies resulting from the 4-week MDI treatment, and electron microscopic examination of hepatocytes revealed no deleterious effects of either MDIs.