β-methyl-digoxin

Summary

The tissue/plasma ratio of β-methyl-digoxin for cardiac muscle in cats was about the same 24 h after a single dose of 30 μg/kg as after a loading dose of 30 μg/kg followed by 3 maintenance doses of 7.5 μg/kg at 24 h intervals. The ratio for the brain increased 2-fold during that time.

After the i.v. injection of a toxic loading dose of 70 μg/kg β-methyl-digoxin or digoxin, maintenance doses of as little as 15 μg/kg at 48 h intervals sufficed to maintain the minimum plasma glycoside concentrations determined by RIA at about 3 ng/ml. There was no difference in the plasma concentrations or in the severity of intoxication produced by both glycosides.

Cats vomited within 3 h after i.v. injection of 100 μg/kg β-methyl-digoxin, whereas a loading dose of 30 μg/kg followed by 3 injections of 7.5 μg/kg at 24 h intervals were well tolerated. The concentration of radioactivity in the brain 3 h after 100 μg/kg was less than 24 h after the last injection of 7.5 μg/kg in the experiments with repeated dosage.

Cerebral side-effects such as vomiting, loss of appetite and weight were better correlated with the glycoside concentrations in the plasma than with those in the brain.