Cardiac Glycosides

Cardiac glycosides consist of a non-sugar part ( aglycon or genin) and sugars (glycon). The basis of aglycon is a steroid ( cyclopentaneperhydrophenanthrene ) structure, which is associated in most glycosides with an unsaturated lactone ring. Glycon can be represented by different sugars: D-digitoxose, D-glucose , D-cymarose, D-ramnose , etc. Sometimes, the residue of acetic acid is attached to the sugar part. The cardiotonic effect of cardiac glycosides is associated with the aglycon portion of the molecule. The sugar part is responsible for the solubility and retention of the molecule in the tissues. Glycon also affects the activity and toxicity of compounds.

Cardiac glycosides easily undergo enzymatic , acidic and alkaline hydrolysis . The enzymes that break down cardiac glycosides are found in plants, which makes possible the breakdown of primary (genuin) glycosides in medicinal raw materials during storage, transportation and preparation for processing. Enzymes can be inhibited to prevent this process.

• cardiac glycosides obtained from digitalis purpurea (Digitalis purpurea):
  • digitoxin
  • cordigit .
• cardiac glycosides obtained from digitalis woolly (Digitalis lanata):
  • digoxin
  • acetyldigitoxin ,
  • acetyldigoxin
  • acetylgitoxin
  • Gitoxin
  • celanide
  • lantoside .
• cardiac glycosides obtained from strophanthus Combe (Strophanthus Kombe):
  • strophanthin K.
• cardiac glycosides derived from May lily of the valley (Convallária majális):
  • korglikon
  • tincture of lily of the valley.
• cardiac glycosides derived from spring adonis (Adonis vernalis):
  • infusion of adonis herb,
  • dryflower extract ,
  • adoniside
  • adonis bromine .

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  Digitalis purple

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  Digitalis woolly

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  Strofant Combe

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  May lily of the valley

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  Adonis spring

The main mechanism of action is the inhibition of the enzyme Na ⁺ / K ⁺ ATPase , which is responsible for the removal of 3 sodium ions from cardiomyocytes into the extracellular matrix and 2 potassium ions in the opposite direction. The resulting increase in the concentration of sodium ions in cardiomyocytes leads to inhibition of the sodium-calcium exchanger , which removes 1 calcium ion from the cardiomyocyte in exchange for 3 sodium ions from the extracellular fluid into the cardiomyocyte. The consequence of this is an increase in the level of calcium in the cytosol of cardiomyocytes, a better activation of the actomyosin complex and an increase in the effectiveness of contraction.

Cardiac Glycoside Effects

• Positive inotropic effect (cardiotonic effect) arising due to an increase in the concentration of calcium in cardiomyocytes and an increase in actin with myosin .
• The negative chronotropic effect associated with the excitation of the baroreceptor depressor reflex due to the excitation of the amplified systolic wave of baroreceptors of the aortic arch and synocarotid zone. The consequence of this is an increase in the tone of the vagus nerve and a slowdown in the generation of action potentials in the sinoatrial node. The tone of the vagus nerve is also increased due to the cardio-cardial reflex. The baroreceptors of cardiomyocytes capture increased contraction of cardiomyocytes and transmit this information via afferent nerve fibers to the dorsal nucleus of the vagus nerve.
• A negative dromotropic effect also occurs due to an increase in the tone of the vagus nerve and a slowdown in conductivity in the atrioventricular node.
• Positive batmotropic effect (undesirable effect) associated with the blockade of Na ⁺ / K ⁺ ATPase, delay of Na ⁺ ions in the cell and a decrease in the level of resting potential. Because of this, cardiac glycosides cause arrhythmias: translate atrial flutter into their fibrillation ( fibrillation ), cause ventricular extrasystole, and in case of an overdose, ventricular fibrillation .

• Glycosides
• Digoxin

• Ed. prof. R.N. Alayautdina. Pharmacology: a textbook. - 4th ed., Revised. and additional .. - Moscow: "GEOTAR-Media", 2010. - S. 377, 423-431. - 832 s. - ISBN 978-5-9704-1428-6 .

• Small medical encyclopedia. Cardiac glycosides. // dic.academic.ru