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What is the primary mechanism of action of cardiac glycosides on myocardial cells?
What is the primary mechanism of action of cardiac glycosides on myocardial cells?
What is the classification of cardiac glycosides based on their chemical structure?
What is the classification of cardiac glycosides based on their chemical structure?
What is the effect of cardiac glycosides on electrolyte balance in myocardial cells?
What is the effect of cardiac glycosides on electrolyte balance in myocardial cells?
What is the major source of cardiac glycosides?
What is the major source of cardiac glycosides?
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What is the toxic effect of excessive doses of cardiac glycosides?
What is the toxic effect of excessive doses of cardiac glycosides?
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What is the secondary effect of cardiac glycosides on the body?
What is the secondary effect of cardiac glycosides on the body?
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What is the effect of cardiac glycosides on the vagus nerve?
What is the effect of cardiac glycosides on the vagus nerve?
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What is the primary indication for the use of cardiac glycosides?
What is the primary indication for the use of cardiac glycosides?
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What is the direct consequence of inhibiting Na+/K+-ATPase enzyme by digoxin?
What is the direct consequence of inhibiting Na+/K+-ATPase enzyme by digoxin?
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Which of the following conditions increases the risk of digitalis-induced arrhythmia?
Which of the following conditions increases the risk of digitalis-induced arrhythmia?
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What is the characteristic of Cardenolides?
What is the characteristic of Cardenolides?
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What is the result of concurrent use of foxglove and calcium?
What is the result of concurrent use of foxglove and calcium?
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Which plant family is known to produce Bufadienolides?
Which plant family is known to produce Bufadienolides?
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What is the consequence of Na+/K+-ATPase inhibition on potassium levels?
What is the consequence of Na+/K+-ATPase inhibition on potassium levels?
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What is the effect of hypokalemia on digoxin binding?
What is the effect of hypokalemia on digoxin binding?
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Which of the following is NOT a medicinal plant source of cardiac glycosides?
Which of the following is NOT a medicinal plant source of cardiac glycosides?
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What is the effect of combining sugar with the aglycone in cardiac glycosides?
What is the effect of combining sugar with the aglycone in cardiac glycosides?
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What is the importance of the β-oriented lactone in cardiac glycosides?
What is the importance of the β-oriented lactone in cardiac glycosides?
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What happens to the activity of cardiac glycosides when the lactone ring is opened?
What happens to the activity of cardiac glycosides when the lactone ring is opened?
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What is the effect of changing the β-hydroxyl group at C-14 to the α-position?
What is the effect of changing the β-hydroxyl group at C-14 to the α-position?
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What is an early symptom of cardiac glycoside toxicity?
What is an early symptom of cardiac glycoside toxicity?
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What is the effect of acid hydrolysis on cardiac glycosides?
What is the effect of acid hydrolysis on cardiac glycosides?
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What is the effect of changing the cis junction of A/B and C/D rings?
What is the effect of changing the cis junction of A/B and C/D rings?
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What is the effect of changing the β-orientation of the C-3 OH and lactone at C-17?
What is the effect of changing the β-orientation of the C-3 OH and lactone at C-17?
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Study Notes
Cardiac Glycosides
- Combination of sugar with the aglycone increases both potency and toxicity of the active principle.
- The sugar affects physical properties such as water solubility and diffusion through semipermeable membranes, influencing the rate of absorption and transport of the compound to the site of action.
Structure-Activity Relationships
- Unsaturation of the β-oriented lactone is essential for activity.
- Opening of the lactone ring renders the glycosides inactive, and saturation results in a substantial decrease of activity.
- β-Orientation of the C-3 OH and lactone at C-17 is important; if it changes to α-orientation, the activity is weaker.
- Activity is stronger if A/B and C/D junctions are cis.
- The β-hydroxyl group at C-14 is important for activity; change to the α-position leads to loss of activity.
Toxicity
- Early symptoms of ingestion include nausea, vomiting, diarrhea, abdominal pain, mild hallucinations, delirium, and severe headache.
- Later symptoms may include irregular and slow pulse, tremors, convulsions, and various cerebral disturbances, especially of a visual nature.
- Digitalis poisoning can cause heart block or tachycardia, depending on the dose and the condition of one's heart.
Hydrolysis of Cardiac Glycosides
- Acid hydrolysis splits sugars from the aglycone, cleaving glycosidic linkages and giving aglycones and sugars.
Mechanism of Action of Cardiac Glycosides
- Cardiac glycosides inhibit Na+/K+-ATPase, the "sodium-potassium pump", causing more Na+ to remain inside myocardial cells.
- Increased intracellular Na+ stimulates Na+/Ca++ exchange, bringing more Ca++ inside heart cells to increase the force of contraction.
- This action indirectly increases the calcium concentration reaching the contractile proteins.
Effects of Administration of Electrolytes
- ↓K+, ↑Ca++, ↓Mg++ → toxicity
- Hypercalcemia increases the risk of digitalis-induced arrhythmia.
- Hypokalemia results in increased digoxin binding, increasing its therapeutic and toxic effects.
- Hypomagnesemia can sensitize the heart to digitalis-induced arrhythmias.
Occurrence
- Medicinally important glycosides are obtained from a limited number of plant families, including Scrophulariaceae, Apocyanaceae, Ranunculaceae, Liliaceae, and Ranunculaceae.
- Cardiac glycosides are classified into two types: cardenolides and bufadienolides, based on the type of lactone ring.
Cardio-Active Glycosides
- Definition: Cardiac glycosides are naturally occurring steroidal glycosides that act as cardiotonic agents.
- Cardiotonic drugs increase myocardial contractility without a corresponding increase in O2 consumption.
- They have a specific and powerful action on the cardiac muscle when administered into man or animal.
Congestive Heart Failure
- Definition: Contractile function is reduced below normal due to disease or lifestyle.
- Manifestation: Blood accumulates in the heart, lungs, abdomen, and lower extremities.
Medicinal Importance
- Cardiac glycosides are used to treat Congestive Heart Failure (CHF).
- They increase the force of contraction of cardiac muscles without increasing oxygen consumption.
- They also increase cardiac output and treat atrial arrhythmias, such as atrial fibrillation and atrial flutter.
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Description
This quiz explores the role of sugar units in cardiac glycosides, including their effects on potency, toxicity, and physical properties. Learn about the different types of sugar units found in these compounds.
