Digitoxin
Synonyms
Cardiac glycosides
definition
Digitoxin is an active ingredient that belongs to the group of cardiac glycosides. Among other things, it improves the beating power of the heart and is therefore prescribed for heart failure, for example.
origin
Digoxin and Digitoxin can be extracted from the same plant: Dem thimble (Latin: digitalis), which is why they are sometimes synonymous with the term digitalis or Digitalis glycosides described.
Effect and mechanism of action
Digitoxin affects the heart as follows:
- Increase there the contact force of the heart muscle (positive inotropic)
- Delay in the transmission of excitation from the area of the atrium (antrum) to the chambers of the heart (ventricle) (negative dromotropic)
- Reduction in beat frequency (negative chronotropic effect).
physiology
The increase in the contraction force of the heart occurs through the following mechanisms:
- Sodium-Potassium ATPase - 3 sodium ions to the outside, 2 potassium ions to the inside (each against the natural concentration gradient, i.e. energy-consuming)
- Sodium-calcium exchanger - 3 sodium per natural gradient inwards, 1 calcium against the natural gradient outwards.
- Cardiac glycosides - Inhibition of sodium-potassium-ATPase, thus less sodium outside. This leads to an indirect inhibition of the sodium-calcium exchanger, which ultimately leads to an increased intracellular calcium concentration.
Pharmacokinetics
Digoxin and Digitoxin differ in terms of their pharmacological properties.
Digitoxin: Its bioavailability when taken as a tablet is almost 100%. It will share about that kidney (renal) and in part via the liver (hepatic) eliminated. His Half-life is 5-7 days.
Indications
Digitoxin is used for the following indications:
- Heart failure (Pumping weakness of the heart)
- Atrial flutter and flicker (by delaying the conduction of excitation)
Side effects
Digitoxin has a narrow therapeutic index. That means it's very easy to overdose on them, resulting in a poisoning (Intoxication) leads. The sodium-potassium pump should only be inhibited in moderation, as otherwise the entire cell stability will be shaken. Symptoms of overdose can include:
- at the Hearts: Cardiac arrhythmias how Ventricular fibrillation, Extrasystoles in the ventricular muscles, AV block
- in the central nervous system: Color vision problems, tiredness, confused states
- in the Gastrointestinal tract: Nausea, Vomit
The therapy one Digitoxin intoxication consists in the gift of Potassium-containing infusion solution (because an increased potassium concentration displaces the cardiac glycosides from the sodium-potassium-ATPase and thus inhibits their effect), Antiarrhythmics (Drugs that limit the cardiac arrhythmias that may be triggered), Digitalis antibodies (which specifically capture free cardiac glycoside molecules and thus render them ineffective).
Interactions
Many factors and the parallel administration of other drugs can reduce the risk Digitoxin effect influence, therefore a precise anamnesis (systematic questioning of the patient about previous illnesses, medication intake, etc.) must be carried out before prescribing and taking. Factors that can cause interactions include:
Potassium concentration – Hyperkalemia (increased potassium concentration) leads to reduced effectiveness, Hypokalemia (reduced potassium concentration), on the other hand, intensifies the effect and can thus - if a normal dose is given - lead to symptoms of intoxication
Renal failure - Patients with dysfunction of the kidneys should not be treated with digoxin; digitoxin should be used here, as it is less excreted via the kidneys
Medication, the drug-degrading enzymes of the liver activate or inhibit (Induction or repression of CYP enzymes). These include some Antibiotics, Anti-epileptic drugs, Johannis herbs and antiarrhythmics.
