Origin and chemical properties
Cardiac glycosides of this group are of plant origin, yet they are extracted from different raw materials:
- Strophanthin (also known as ouabain or strophanthin G) is a glycoside extracted from the seeds of tropical Strophanthus plants, specifically the species Strophanthus gratus and Strophanthus kombe.
- Corglycone is a drug containing a sum of glycosides isolated from the leaves of the lily of the valley (Convallaria majalis).
From a physicochemical standpoint, a key characteristic of these drugs is that they are polar compounds. It is precisely the high polarity of the molecules that fundamentally dictates their entire subsequent pharmacokinetics, routes of administration into the body, and the specifics of their clinical use as emergency therapy.
Pharmacokinetics of polar glycosides
The pharmacokinetic profile of strophanthin and corglycone directly stems from their polar structure. They behave in the body quite differently from lipophilic glycosides.
Absorption and distribution Polar molecules are practically incapable of being absorbed from the gastrointestinal tract. For this reason, oral administration of these medications is pointless — the route of administration can be intravenous only. Upon entering the systemic circulation, the drugs bind to plasma proteins at a relatively low level — approximately 40%.
Metabolism and elimination Unlike many other cardiovascular drugs, polar glycosides do not undergo biotransformation. They are completely un-metabolized by enzyme systems. Elimination occurs via renal function: the drugs are excreted in an absolute unchanged form.
The problem of accumulation The capacity for material accumulation (buildup in the body) for strophanthin and corglycone is significantly less pronounced compared to classic digitalis glycosides. This is explained by their short-lived circulation in the bloodstream. Nevertheless, despite the reduced risk, the danger of developing glycoside intoxication during their use persists entirely, requiring strict dosage control.
Time parameters and character of action
Because the drugs are administered directly into a vein and do not require time for absorption from the intestine, they act as typical emergency medical treatments.
For strophanthin (ouabain), the following time intervals are characteristic:
- Latent period: extremely short. The first signs of a therapeutic effect develop within 2 to 20 minutes after injection.
- Peak of action: maximum intensity of effect occurs in 30–120 minutes.
- Duration: the total duration of the drug's action ranges from 1 to 3 days.
Comparison with corglycone: Corglycone is very close to strophanthin in its pharmacological action and main pharmacokinetic parameters. Their main difference lies in the duration of action: corglycone exerts a somewhat more prolonged effect on the myocardium.
Indications and administration rules
The primary niche for polar cardiac glycosides is situations requiring immediate intervention to support cardiac function.
Indications for prescribing:
- First and foremost, this is acute heart failure (AHF) — the main indication for both strophanthin and corglycone.
- Chronic heart failure (CHF) of severe stages, specifically functional classes III–IV (strophanthin is used).
- Tachy-form of atrial fibrillation (also an indication for strophanthin administration).
Method of administration: Drug administration is associated with certain safety rules. The injection must be performed intravenously and very slowly. To ensure uniform and safe entry of the drug into the bloodstream, the glycosides are preliminarily diluted in a glucose solution. Rapid administration is strictly prohibited due to the risk of developing severe complications.
Briefly: answers to topical questions
Which specific blood plasma proteins do strophanthin and corglycone bind to, and what is the percentage of this binding?
Strophanthin binds to blood plasma proteins by approximately 40%. The exact names of the specific plasma proteins it binds to are not indicated in the presented materials. For corglycone, it is noted that it is close to strophanthin in its character of action and pharmacokinetics, but the exact percentage of plasma protein binding and the names of specific proteins are not provided in the sources. Strophanthin is a polar compound, practically unabsorbed from the gastrointestinal tract, not metabolized, and excreted by the kidneys unchanged.
What clinical symptoms are characteristic of strophanthin glycoside intoxication?
A detailed list of clinical symptoms of intoxication specifically from strophanthin is absent in the presented materials. For strophanthin, it is indicated that accumulation is less pronounced compared to digitalis glycosides, but the risk of intoxication persists. The materials also indicate that nausea and vomiting may be signs of glycoside intoxication in digoxin overdose.
What contraindications exist for prescribing strophanthin and corglycone?
In the presented materials, contraindications for prescribing cardiac glycosides, including digoxin, strophanthin, and corglycone, are indicated in the context of treating circulatory failure in congenital heart defects. These include:
- conduction and rhythm disorders: bradycardia, atrioventricular blocks, paroxysmal ventricular tachycardia;
- severe renal pathology: anuria;
- specific anatomical defects: aortic coarctation, aortic stenosis, Tetralogy of Fallot.
Which drugs are used as antidotes in strophanthin poisoning?
As antidote therapy for cardiac glycoside therapy complications, the presented materials list:
- Digibind — monoclonal antibodies that bind cardiac glycosides into inactive complexes.
- Unithiol — a sulfhydryl group donor; forms disulfide bridges with the glycoside molecule, frees up the intrinsic thiol groups of Na+,K+-ATPase, and restores the transport function of the enzyme.
Trilon B, potassium chloride, Panangin, and Asparkam are indicated as treatments for complications of cardiac glycoside therapy, but are not named as antidotes in the sources.
Remembering the origin by first letters: Strophanthin is obtained from Strophanthus Seeds, while korglykon (recall the root “glykon” and lily of the valley) is extracted from Lily of the Valley Leaves.
Class and exam questions
Why are strophanthin and corglycon not prescribed in tablet form?
These drugs are pronounced polar compounds. Due to their chemical structure, they are practically unabsorbed from the gastrointestinal tract, so oral administration will not yield any therapeutic effect.
Which organ is responsible for the elimination of these drugs from the body?
Elimination is carried out exclusively by the kidneys. At the same time, the drugs leave the body in a completely unchanged form, as they do not undergo metabolism.
What is the main clinical difference between corglycon and strophanthin?
Both drugs are very close in action and pharmacokinetics, however, the clinical effect of corglycone administration persists slightly longer than that of strophanthin.
How to properly administer these glycosides intravenously?
The drugs must be administered intravenously very slowly. A glucose solution must be used as a solvent for infusion or slow injection.
What else to study on this topic
- Mechanisms of development of glycoside intoxication using polar glycosides.
- Comparative characteristics of the pharmacokinetics of digitalis and strophanthus glycosides.
- Features of strophanthin use in the tachy-form of atrial fibrillation.
- Criteria for determining functional classes III and IV of chronic heart failure.
- The role of glucose solution in the intravenous administration of cardiac glycosides.
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