Origin and Chemical Properties
Cardiac glycosides of this group are of plant origin, but they are extracted from different raw materials:
- Strophanthine (also known as ouabain or strophanthin G) is a glycoside extracted from the seeds of tropical plants of the genus Strophanthus, specifically Strophanthus gratus and Strophanthus kombe.
- Corglycon is a preparation containing a mixture of glycosides isolated from the leaves of lily of the valley (Convallaria majalis).
From a physicochemical standpoint, their key characteristic is that they are polar compounds. This high molecular polarity fundamentally determines their pharmacokinetics, routes of administration, and clinical use in emergency therapy.
Pharmacokinetics of Polar Glycosides
The pharmacokinetic profile of strophanthine and corglycon stems directly from their polar structure. They behave quite differently in the body compared to lipophilic glycosides.
Absorption and Distribution Polar molecules are practically incapable of being absorbed from the gastrointestinal tract. Therefore, oral administration is ineffective — the route of administration must be intravenous only. Upon entering the systemic circulation, the drugs bind to plasma proteins at a relatively low rate of approximately 40%.
Metabolism and Elimination Unlike many other cardiovascular agents, polar glycosides do not undergo biotransformation and are not metabolized by enzyme systems. Elimination occurs entirely via renal excretion, with the drugs eliminated in an unchanged form.
The Issue of Cumulation The potential for material cumulation (accumulation in the body) is significantly lower for strophanthine and corglycon compared to classic digitalis glycosides. This is explained by their short circulation time in the bloodstream. Nevertheless, despite the reduced risk, the danger of glycoside toxicity remains present, requiring strict dosage control.
Time Parameters and Nature of Action
Because these drugs are administered directly into a vein and do not require intestinal absorption, they function as typical emergency medications.
For strophanthine (ouabain), the time intervals are as follows:
- Latent period: extremely short. The first signs of a therapeutic effect develop between 2 and 20 minutes after injection.
- Peak effect: maximum intensity is reached within 30–120 minutes.
- Duration: total duration of action ranges from 1 to 3 days.
Comparison with Corglycon: In terms of pharmacological action and basic pharmacokinetic parameters, corglycon is very similar to strophanthine. Their main difference lies in the duration of action: corglycon exerts a slightly more prolonged effect on the myocardium.
Indications and Administration Guidelines
The primary niche for polar cardiac glycosides is acute situations requiring immediate intervention to support cardiac function.
Indications for Use:
- Primarily acute heart failure (AHF), which is the main indication for both strophanthine and corglycon.
- Severe stages of chronic heart failure (CHF), specifically New York Heart Association (NYHA) functional classes III–IV (strophanthine is used).
- Tachyarrhythmic form of atrial fibrillation (also an indication for strophanthine).
Route of Administration: Administration requires adherence to safety rules. Injections must be performed intravenously and very slowly. To ensure uniform and safe delivery into the bloodstream, the glycosides are pre-diluted in a glucose solution. Rapid administration is strictly prohibited due to the risk of severe complications.