Describe the physiological basis for the positive inotropic effect of digoxin on the heart. How does this explain the therapeutic benefit of the drug?

Digoxin is a sodium potassium adenosine triphosphatase (Na+/K+ ATPase) inhibitor.

Digoxin is a group of drug that has most effects on cardiac tissues. Digoxin was first isolated from the plant Digitalis lantana that was found to be a sodium potassium adenosine triphosphatase (Na+/K+ ATPase) inhibitor. This drug when taken through mouth, gives a 60 to 80% bioavailability .

This drug blocks the sodium potassium adenosine triphosphatase (Na+/K+ ATPase) pumps of the myocardium. When the sodium pumps are closed, this leads to the increase in extracellular levels of sodium.

As the extracellular sodium increase, this indirectly blocks the sodium calcium exchanger which in normal conditions exchange 1 intracellular calcium in exchange of 3 extracellular sodium ions.

As this pump is blocked, this leads to increase in intracellular levels of calcium. This calcium levels also increase in the sarcoplasmic reticulum. Thus, the contractibility of the heart muscles per beat increase which helps to pump blood more effectively. Thus, the effect seen is positive intropic effect.

a- multicellular

b-eukaryotic

c-no cell wall

d-heterotrophic

e-autotrophic

silt loam

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