Cardiac glycosides are medicines for the heart that are developed from certain poisonous plants, such as lily of the valley, Christmas rose, foxglove, oleander, and white water lilies. From these plants, medicines have been developed to control tightening contractions in a heart condition known as angina, as these compounds, developed from a plant hormone, relax the heart contractions by boosting the cells of the heart to become better at absorbing electrolytes such as sodium. Improved sodium absorption also leads to subsequent assistance towards better calcium absorption for both the heart and kidneys. Digitonin, developed from the purpurea plant, is used to improve the systolic or maximum blood pressure during a heartbeat. Digitonin also increases the length of diastolic or minimum blood pressure phases, when the heart is between beats, to assist in conditions of congestive heart disease.
Glycosides are actually compounds containing non-carbohydrate and carbohydrate residues and bond with non-sugar components known as aglycone and sugar components known as glycone. When the carbohydrate is dominantly glucose, it becomes known as a glucoside or glycoside. Some glycosides turn to cortisol and cortisone steroids in the kidney and help to stabilize enzymes that are healthy for the heart.
The cardiac glycoside digitalis and all of its forms is the most common prescription medication for congestive heart failure (CHF) disease. Digoxin helps the heart to become a more efficient pump, as it boosts the strength and force of myocardial contractions and helps to keep CHF patients from developing enlarged hearts. A tropical plant called strophanthus has a milky poisonous substance that in minute quantities can produce heart failure and death; however, as a medicine, it takes effect quicker and lasts longer than digitalis. For patients with weak, enlarged hearts that don’t pump well, strophanthin effects more force to the maximum pressures during a heartbeat to improve the heart’s sufficiency. Dosage differences between assistance and life-threatening damage are very slight in all these medications, so caution is advised.
There are two special receptors in heart muscles where cardiac glycosides bond and aid in boosting the force of contractions. One receptor is considered high affinity and the other is low affinity, according to some studies. These receptor sites also bear a relation to conditions of hyperthyroidism when the thyroid overworks, and some ischemic heart disease conditions. Some people have been found to have a mutated gene that makes them resistant to help from cardiac glycosides at these receptor sites.
Some cardiac glycosides have effects on the heart other than those already listed, yet related. Due to the systolic and diastolic blood pressure improvements, there is a slower, more stable, heartbeat. This stability signals renewed vitality in the heart and, thus, a flow of impulses to vascular nerves returns to improve overall blood circulation.