Glycoside cardiotonic

The glycosides cardiotonics are Médicament S used in the treatment of the Cardiac failure or the cardiac arrhythmia, by inhibition of the Pompe sodium/potassium. This inhibition increases the quantity of Ca⁺⁺ ions available for the contraction, improves the cardiac flow and reduces the distension of the heart.

The glycosides cardiotonics are extracted from plants:

Digitalis lanata and Digitalis purpurea (the Digoxine, the Métildigoxine and the Digitoxine used into therapeutic)
for memory:

the Strophantus (the Ouabain used mainly for the medical research)
the maritime Squill ( Scilla maritima ) (the proscillaridine A)
the Lily of the valley of May ( Convalaria majalis ) (convalatoxine).

They have an effect Antiarythmique by prolongation of the refractory period of the auriculo-ventricular Nœud, thus reducing the frequency of the impulses. The cardiac flow is restored without the auricular Fibrillation not being removed. Their use is very delicate and requires an assiduous medical supervision.

The overdose led to the digitalic Intoxication.

Mode of action at the cardiac level

Heterosides cardiotonics function while interacting with a pump/membrane enzyme, Na⁺/K⁺ ATPase. This pump is charged to restore and/or maintain the distribution nonsymmetrical of the ions on both sides of the plasmic membrane of the cells person in charge of the hyperpolarisation (electric) negative of the interior of the cellule.
At the time of a potential of action (brutal depolarization of the membrane), which will involve a muscular contraction (or cardiac for example), the contraction will be all the more intense as the potential of action will be prolonged, on the other hand, the muscular fabric (and highly-strung person) will be refractory has a new potential of action as long as Na⁺/K⁺ ATPase will not have restored a negative potential of membrane. In addition a cell whose potential of rest will be higher than the normal will be more excitable.
Heterosides cardiotonics inhibit Na⁺/K⁺ ATPase and thus cause an increase in the muscular force of contraction, but slow down the repolarization by thus delaying the following cardiac contraction. Their effects are thus known as:

positive Inotrope (increase in the force of contraction)
Chronotropic negative (reduction in the heart rate)
negative Dromotrope (reduction the speed of conduction atrio-ventricular)

positive Bathmotrope (increase in muscular exitability)

Effect on other Na⁺/K⁺ ATPases

Renal

how will operate cardiotonic the tube renal

Retina

Muscle