Summary
The tissue distribution and the positive inotropic effect of α- and β-methyl-digoxin, digoxin, and digitoxin were investigated in cats under pentobarbital anaesthesia, the emetic effect of β-methyl-digoxin and digoxin in unanaesthetized animals.
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1.
The distribution volume calculated by dividing the injected dose by the concentration in the plasma water after 60 min decreased in the order digitoxin > β-methyl-digoxin ≥ α-methyl-digoxin > digoxin.
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2.
The distribution coefficients between tissue and plasma water decreased for all glycosides in the order kidney > liver > heart > diaphragm > erythrocytes > perirenal fat > brain.
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3.
α-Methyl-digoxin and digoxin were metabolized to a larger extent than were β-methyl-digoxin and digitoxin.
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4.
200 nmoles/kg digoxin produced arrhythmias, whereas equimolar doses of the other glycosides were well tolerated.
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5.
Except for α-methyl-digoxin, there was a close relation between the increase in dp/dt max and the concentration in the plasma water 60 min after the injection. The differences in the equieffective doses of β-methyl-digoxin, digoxin, and digitoxin can therefore be explained by the differences in tissue distribution.
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6.
Although higher concentrations of β-methyl-digoxin than of digoxin were found in the brain, there was no difference in the central activity of the two glycosides.
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Schaumann, W., Koch, K. β-Methyl-digoxin. Naunyn-Schmiedeberg's Arch. Pharmacol. 286, 195–210 (1974). https://doi.org/10.1007/BF00501612
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DOI: https://doi.org/10.1007/BF00501612