Found in the leaves of plants (eg. Foxglove). Contain compound glycoside.
Cardiac Glycoside- Used For
Primarily Tx of CHF
Cardiac Glycoside- Pharmacological Effects
Increased force of myocardial contraction (does not appreciably increase O2 consumption), improving efficiency of the heart. Decreases HR and AV conduction speed, stimulation of vagus nerve and depressing action of AV node.
Cardiac Glycoside- Characteristic ECG changes
Therapeutic doses: ST depression, T wave alteration, increased PR interval=lengthened conduction time. Higher doses: Potential for heart conduction blockages.
Cardiac Glycoside- Mycardium Contractility
Inhibits ATPase=no ATP to power Na+/K+ pump. Na+ accumulates inside the cell, resulting in more activity of the Na+/Ca++ pump bringing more Ca++ inside the cells. Allows for better contraction of the heart muscle. Contractions will also be SHORTER d/t alteration in Ca++ levels.
Cardiac Glycoside- AV Conduction
Interference with Na+/K+ pump slows the return of K+ back into contractile cells after action potential. Slowed repolarization and prolonged REFRACTORY period.
(Lanoxin) Cardiac Glycoside.
(Digitoxinum) Cardiac Glycoside.
"front loading" of a drug. Drug given at higher and more frequent doses in order to rapidly achieve therapeutic levels.
Low term usage. Lower and less frequent levels to maintain the therapeutic level.