Products
Preparations from the leaves of foxglove are rarely used medicinally today. Medicines containing the ingredient digitoxin are available in some countries. Digoxin, the pure substance extracted from foxglove, is commercially available in many countries in the form of tablets (Digoxin Sandoz).
Stem plant
Red foxglove, a member of the plantain family (Plantaginaceae), is native to Europe. Used is also the woolly foxglove . Previously, the plants were assigned to the family Scrophulariaceae.
Medicinal drug
Digitalis purpurea leaves (Digitalis purpurea folium) are used as a medicinal raw material. It is the dried leaves of . The pharmacopoeia requires a minimum content of cardenolide glycosides, calculated as digitoxin. Adjusted extracts, powders and tinctures are prepared from the leaves.
Ingredients
The leaves contain cardiac glycosides of the cardenolide type, also known as digitalis glycosides. Digitoxin is a typical example, but not digoxin. Incidentally, the two substances differ only in a single oxygen atom.
Effects
Digitalis glycosides have the following properties:
- They increase the contractile force and speed of the heart (positive inotropic).
- They decrease the heart rate (negative chronotropic).
- They delay the conduction of excitation (negative dromotropic).
- They increase excitability, especially in the ventricular muscles (positive bathmotropic).
The glycosides remain in the body for a long time. Digitoxin has a half-life in the range of 7 to 8 days. Digoxin’s half-life is shorter at 40 hours.
Indications for use
- For the treatment of heart failure.
- For the treatment of cardiac arrhythmia.
Dosage
Caution: foxglove is a poisonous plant. Only finished medicines should be taken. The leaves or other parts of the plant should not be prepared as a tea or administered in any other form. Relevant cases of poisoning have been documented in the literature.
Abuse
Foxglove has been abused for poisoning and suicide in the past.
Contraindications
For complete precautions, see the drug label.
Adverse effects
The most common possible adverse effects include headache, drowsiness, fatigue, weakness, cardiac arrhythmias, drowsiness, nausea, vomiting, diarrhea, and poor appetite. These indications refer to cardiac glycosides. The active ingredients have a narrow therapeutic range. Overdose, accidental ingestion of plant parts, or confusion with edible plants is life-threatening. It can lead to dangerous cardiac arrhythmias, ventricular fibrillation, heart block and cardiac arrest. In addition, digestive disorders (e.g., nausea, vomiting), hyperkalemia, and neurotoxic effects often occur. However, poisoning is rare due to the bitter taste. Foxglove can be confused with comfrey (see literature). The Fab fragment of an antibody is available as an antidote (DigiFab).
