medicinal herbs

Digitalis Purpurea - therapeutic uses and toxicity

Introduction

The digitalis - pharmacological products made up of digitalis molecules of natural derivation ( Digitalis purpurea ) or synthetic - have a very low therapeutic index: in simple words, it means that the limit between the therapeutic dose and the toxic dose is very thin, consequently the dosages must be scrupulous and careful, and the patient who undergoes digital treatment must be constantly monitored.

However, the toxicity symptoms induced by the administration of Digitalis purpurea are very frequent.

Digitalis purpurea: toxicity

FUI indicates that the leaves of Digitalis purpurea cannot contain less than 0.3% of cardenolidic heterosides, expressed as digitoxin (drug marker), calculated on a dry drug.

It is estimated that only 40 grams of fresh leaves of Digitalis purpurea can kill a man: the fatal dose drops to 10 grams for the dried drug.

A fresh leaf, containing about 80% water, may consist of a variable amount of heterosides, generally between 1.6 and 4.8 mg, as well as saponoside molecules (capable of altering the absorption of heterosides at the intestinal level).

Medical use and properties

Despite the existence of numerous species belonging to the genus Digitalis, only D. purpurea and D. lanata are used in the medical field for the extraction of cardiotonic active substances.

The most important activity is certainly the cardiotonic one, whose mechanism of action is summarized as follows:

Increased myocardial cell contraction → sodium potassium pump block →

↓ intracellular sodium concentration and ↑ availability of calcium inside the cell

  • Positive inotropic action (↑ contraction force)

Other actions included in the Digitalis purpurea include:

  • Bradycardia, negative chronotropic activity (↓ heart rate)
  • Positive batmotropic effect (↑ excitability of cardiac fibers)
  • Negative dromotropic action (↓ of the impulse transmission speed)

The immediate consequences deriving from the administration of Digitalis purpurea (respecting the prescribed posology) result in the improvement of cardiac function, followed by the strengthening of both the renal plasma flow and the glomerular filtration (diuretic properties). The venous return to the heart, due to vasoconstriction, is weakened.

The use of extracts of Digitalis purpurea is generally recommended for the treatment of congestive cardiac alterations, fibrillation and paroxysmal supra-ventricular tachycardia. [from E. Campanini's Dictionary of herbal medicine and medicinal plants ]

In homeopathy, the mother tincture of fresh leaves of Digitalis purpurea is used to counteract arthritis and digestive difficulties.

Intoxication

Given the dangerousness of the plant it is good to repeat it again: the extracts of Digitalis purpurea can only be administered by the doctor, and their use in phytotherapy or as a "do-it-yourself" natural remedy is absolutely banned. The active ingredients obtained from the leaves - following prolonged therapies or excessive dosages - can generate a series of extremely dangerous effects for the organism; among all are arrhythmias, abdominal pains, nausea, vomiting, anorexia and gastrointestinal disorders in general, dizziness, insomnia, mental confusion, visual deficits, palpitations and syncope (sudden loss of consciousness).

The clinical-toxicological picture can be aggravated when the subject also suffering from renal-hepatic diseases, hypoxia, alkalosis, hypomagnesemia and hypocalcemia, takes at the same time extracts of Digitalis purpurea.