Common names: Foxglove, Dead Men’s Bells, Dog’s Finger, Fairy Gloves, Ladies’ Glove, Witches’ Gloves, Fairy Thimbles
The drug Digitalis, an extract of Digitalis purpurea, Foxglove plant, is in use since long. Medical practitioners, namely, WilliamWithering, 1785 and Hahnemann, 1803, had introduced the drug in their respective systems of medicine. Out of about thirty known organic compounds of Digitalis purpurea only 4–6 are medicinally active components comprising of Digoxin, Digitoxigenin, Digoxigenin, and Saponins.
Digitalis purpurea derivatives are used in treatment of diseases like heart failure, arrhythmia, neurological diseases and also being tried as antitumor. Digoxin (C41H64O14) is 300 times more potent than the powder prepared from Digitalis purpurea. It has a molecular weight of 780.95, and the absolute bioavailability of Digoxin intravenous injection is 100%.
In its first year, this biennial plant produces a rosette of large, oval, textured green leaves covered with a downy silvery hair from which the flowering spike emerges a year later. In its Second year it flowers the whole summer, from June to August.
Reaching 1.5m, it can have from 20-80 hanging blooms in clusters on one side of the stem. Its 4-5cm bell shaped flowers are pinky-purple with spotted throats. Relying on honey bees and bumble bees for pollination, the projecting lower lip of the flowers are perfect landing platforms.
Every part of this native wild flower is known to be poisonous and people were afraid to bring it into their houses or even pick it. It was however used by herbalists as a treatment for different ailments, poultice to reduce swelling, an ointment in treating of open sores and taken boiled in wine as an expectorant.
Botanical Name: Digitalis purpurea (Linn.)
Family: N.O. Scrophulariaceae
Indian Name: Tilpushpi
Health benefits of Digitalis
Digitalis is of value in irritable heart with palpitation from overwork, heart strain, and the arrhythmia of simple dilatation, in moderate degrees of ventricular dilatation, and cardiac asthenia. It is especially commended for the irritable heart of soldiers brought on by long marches and fighting whereby the inhibitory-control is lost or lessened and exhaustion of the heart-muscle is imminent. When palpitation is purely nervous, it is of little value; cactus is then a better remedy. It also fails often in paroxysmal tachycardia, which is also mostly a nervous phenomenon.
In Grave’s disease, it is not curative, but sometimes rectifies the cardiac irregularity. In functional palpitation arising from imperfect digestion it sometimes controls the heart symptoms, but gives little or no relief if the trouble is purely nervous, nor does it aid the stomachic disorder.
Digitalis is a classic example of a drug derived from a plant formerly used by folklorists and herbalists: herbalists have largely abandoned its use because of its narrow therapeutic index and the difficulty of determining the amount of active drug in herbal preparations. Once the usefulness of digitalis in regulating pulse was understood, it was employed for a variety of purposes, including the treatment of epilepsy and other seizure disorders, now considered inappropriate.
Congestive heart failure
Digitalis glycosides have been used clinically for the treatment of CHF for more than 200 years. Digitalis is mainly used in treating heart diseases. In case of congested heart failure, it promotes and stimulates the activity of all muscle tissues.
The herb forces more blood into the coronaries thereby improving the nourishment to the heart. When blood circulation gets impaired and dropsy sets in, digitalis help in restoration and regulation of the function of the heart. It helps urination by improving the blood supply to the kidneys and removes obstructions within the kidneys.
Digitalis is used with gratifying results in some ointment for local application on wounds and burns. In cases of burns, it is very effective in preserving severely damaged cells.
Primary data also reveal potential applications of cardiac glycosides for the treatment of cystic fibrosis. The profound lung inflammation that characterizes cystic fibrosis is mainly attributed to an overproduction of Il8 in the lung. Interestingly, oleandrin has been shown to inhibit Il8-mediated biological responses in diverse cell types by modulating Il8 receptors through altering membrane fluidity and microviscosity.
In agreement with this, therapeutic concentrations of digitoxin were enough to not only suppress hypersecretion of Il8 from cystic fibrosis lung cells in vitro, but to potentially mimic gene therapy with wild-type CFTR. Indeed, comparative gene-expression analysis showed that the majority (62%) of the ‘informative’ genes affected by CFTR gene therapy were similarly affected upon treatment with non-toxic doses of digitoxin
In a recent chemical genetic screen, Wang et al. identified cardiac glycosides — neriifolin, digoxin, digitoxin and ouabain as the molecules with the most potent neuro protective effects in two ex vivo brain explantbased experimental models of ischaemic stroke, as well as in two independent animal models for clinical stroke.
At the same time, studies by Pierre et al. investigating the cardioprotective effects of diaxozide reported that certain compounds, including cardiac glycosides that can cause opening of the mitochondrial ATP-sensitive potassium channels (KATP) might have therapeutic potential for the protection of ischaemic heart tissue.
Indeed, ouabain was shown to protect rat hearts against ischaemia–reperfusion injury. Taken together, these new findings suggest that cardiac-glycoside-based agents might have potential as novel therapies for stroke and heart ischaemia.
In the 1980s, Stenkvist and colleagues reported that breast cancer cells obtained from women on digitalis therapy were characterized by a series of more benign features compared with cancer cells from control patients.
Moreover, 5 years after mastectomy, the recurrence rate of breast cancer among patients on digitalis treatment was 9.6-times lower compared with patients not on digitalis. Around the same time, a second confirmation came from Goldin and colleagues, who studied the effects of digitalis treatment in 127 patients with cancer.
Among the 21 deaths attributed to cancer, only one patient belonged to the digitalis group. However, these encouraging results did not trigger much attention at the time. More recently, Stenkvist reported on 20 years of follow-up data and demonstrated that patients receiving digitalis had a significantly reduced mortality rate (6%, 2/32) compared with the control group (34%, 48/143)73.
The already well-established pharmacodynamics and pharmacokinetics of these compounds provide a shorter pathway to clinical trials. In April 2000, the US Food and Drug Administration (FDA) approved a Phase I study of Anvirzel in patients with advanced solid tumours. Anvirzel is an aqueous extract of the plant Nerium oleander. It contains a variety of compounds including polysaccharides, proteins, sugars and cardiac glycosides — mainly oleandrin and its aglycone oleandrigenin.
It has been demonstrated that Anvirzel inhibits the export of FGF from prostate cancer cells through sodium-pump inhibition by oleandrin. Furthermore, Pathak et al. investigated the mechanisms of Anvirzelinduced cancer cell death in various cancer cell lines of human, murine and canine origin and found that human cells are more susceptible to the effects of this drug. The results of Phase I trials show that Anvirzel can be safely administered to patients with solid tumours.
All parts of the plant are toxic. Animal toxicity occurs during grazing. Children have been made ill by sucking the flowers or ingesting seeds or parts of the leaves. Deaths have been reported among persons who drank tea made from digitalis mistakenly identified for comfrey, although the bitter taste often deters ingestion or its emetic properties can induce vomiting.
Digitalis glycosides are excreted slowly and accumulate; therefore, intoxications during therapy are common. The incidence of digitalis toxicity has been estimated to range from 5% to 23%. More stringent dosing guidelines and monitoring techniques have dramatically reduced the incidence of therapeutic overdose. Digitalis poisoning often is associated with intentional ingestion by adolescents and adults, sometimes with suicidal intent.
Signs of poisoning by the plant or purified drug include contracted pupils, blurred vision, strong but slowed pulse, nausea, vomiting, dizziness, excessive urination, fatigue, muscle weakness, and tremors; in severe cases, stupor, confusion, convulsions, and death occur. Cardiac signs include atrial arrhythmias and atrioventricular block. The cardiac effects are the most dangerous. Chronic digitalis intoxication is characterized by visual halos, yellow-green vision, and gastrointestinal upset. In mild cases of toxicity (atrial fibrillation with a slow ventricular response or occasional ectopic beats), temporary withdrawal of the drug and electrocardiogram monitoring is sufficient.
Gastric lavage or emesis together with supportive measures, such as electrolyte replacements, antiarrhythmics (eg, lidocaine, phenytoin), atropine, and other agents that can antagonize the cardiovascular effects of the glycosides, have been used to manage acute poisonings. Digoxin-specific Fab antibody fragments (Digibind) are effective in managing acute intoxications caused by digitalis and related cardioactive glycosides. This therapy is revolutionary for the severely poisoned patient. Digoxin Fab fragment antibodies by infusion are an effective antidote for some plant cardiac glycosides, but not always for digitalis.