Cardiac Glycosides: Applications and Mechanisms

Cardiac Glycosides: Applications and Mechanisms

Cardiac glycosides are a group of drugs widely used in the treatment of heart failure. The main principle of heart failure treatment is to enhance the contractility of the heart, and glycosides play a crucial role in this.

Origin and commonly used types:

• The two most common sources of glycosides are the foxglove plant (Digitalis) and the Ouabain plant.

• Digitalis (Digitoxin, Digoxin) is more commonly used due to its prolonged action.

Structure and lipid solubility:

• The structure of glycosides consists of two parts: the sugar part (increases bioavailability) and the non-sugar Aglycone part (has anti-heart failure effects).

• Ouabain has the lowest lipid solubility among the three types (Digoxin, Digitoxin, Ouabain) and is only used orally.

Pharmacokinetics:

• The absorption of glycosides is affected by diarrhea and dysentery.

Mechanism of action:

• Glycosides act on the Na/K ATPase pump, inhibiting its activity.

• This inhibition leads to calcium accumulation in cardiac muscle cells, stimulating the calcium pump and enhancing heart contractility.

Effects on the body:

• Heart: Slows, strengthens, and regularizes the heartbeat.

• Blood vessels: In healthy individuals, it causes vasoconstriction and reduces cardiac output; in heart failure patients, it causes vasodilation and increases cardiac output.

• Kidneys: Diuretic effect, increases sodium, potassium, and water excretion.

• Smooth muscle: Increases smooth muscle contraction, which can lead to shortness of breath, abdominal pain, vomiting, diarrhea, and premature birth.

• Nervous system: Causes vomiting, stimulates skeletal muscle.

Indications:

• Congestive heart failure: The most common indication for cardiac glycosides.

• Paroxysmal tachycardia: Digoxin.

• Supraventricular tachycardia: Digitoxin.

Side effects and toxicity:

• Toxicity: Due to glycoside overdose.

• Symptoms of toxicity: Gastrointestinal disturbances, central nervous system disturbances, heart problems.

• ECG: Inverted T wave, ST segment depression, prolonged P-Q interval.

Dosage:

• Digoxin: 0.5-2 ng/ml.

• Digitoxin: 14-26 ng/ml.

Note:

• Glycosides are potent drugs and can cause toxicity if not used correctly.

• The use of glycosides should be closely monitored by a cardiovascular specialist.

• The dosage and method of administration should be strictly followed as instructed by the doctor.