Key result
Methyldigoxin yields greater contractility and a higher arrhythmia threshold than digoxin in guinea pig atria.
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In isolated guinea pig atria, methyldigoxin requires higher concentrations to cause arrhythmias and produces greater contractility than digoxin at equivalent tissue levels.
The chronotropic and inotropic effects as well as the tissue levels of digoxin and methyldigoxin were studied in isolated guinea pig atria. Higher concentrations of methyldigoxin than of digoxin were required to cause arrhythmias. The inotropic potencies of the two glycosides did not differ from each another in equimolar concentrations in the organ bath. The increase in contractility correlated with the level of the glycoside in the organ bath and in the tissue. Digoxin was more effectively taken up by the heart tissue than methyldigoxin. Thus, when the tissue levels of the glycosides were the same, the contractility was greater after methyldigoxin than after digoxin.
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Allonen et al. (1977) studied this question. Methyldigoxin vs. Digoxin was evaluated on Chronotropic and inotropic effects, tissue levels, and arrhythmias. In isolated guinea pig atria, methyldigoxin required higher concentrations to cause arrhythmias than digoxin, but produced greater contractility at equivalent tissue levels.
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