What is/are Lanoxin Tablets?
DIGOXIN is used to treat congestive heart failure and heart rhythm problems. This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.
What should I tell my health care providers before I take this medicine?
They need to know if you have any of these conditions:
- certain heart rhythm disorders
- heart disease or recent heart attack
- kidney or liver disease
- an unusual or allergic reaction to digoxin, other medicines, foods, dyes, or preservatives
- pregnant or trying to get pregnant
How should I use this medicine?
Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. It is best to take this medicine on an empty stomach, at least 1 hour before, or 2 hours after meals. Take your doses at regular intervals. Do not take your medicine more often than directed.
Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.
Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.
Note: This medicine is only for you. Do not share this medicine with others.
What if I miss a dose?
If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.
What may interact with this medicine?
- agents used to treat cancer
- beta blockers or calcium-channel blockers, often used for high blood pressure or heart problems
- calcium, magnesium, or potassium salts
- certain medicines used to decrease cholesterol, including cholestyramine or colestipol
- clarithromycin or erythromycin
- diet pills (stimulants) or drugs used to control weight
- medicines to control heart rhythm like dofetilide, amiodarone, sotalol, and others
- sodium polystyrene sulfonate
- tetracycline antibiotics like doxycycline and tetracycline
- thyroid hormones
This list may not describe all possible interactions. Give your health care providers a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.
What side effects may I notice from this medicine?
Side effects that you should report to your doctor or health care professional as soon as possible:
- allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
- changes in behavior, mood, or mental ability
- changes in vision
- fast, irregular heartbeat
- feeling faint or lightheaded, falls
- nausea, vomiting
- unusual bleeding, bruising
- unusually weak or tired
Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
- breast enlargement in men and women
This list may not describe all possible side effects.
What should I watch for while using this medicine?
Visit your doctor or health care professional for regular checks on your progress. Do not stop taking this medicine without the advice of your doctor or health care professional, even if you feel better. Do not change the brand you are taking, other brands may affect you differently.
Check your heart rate and blood pressure regularly while you are taking this medicine. Ask your doctor or health care professional what your heart rate and blood pressure should be, and when you should contact him or her. Your doctor or health care professional also may schedule regular blood tests and electrocardiograms to check your progress.
Watch your diet. Less digoxin may be absorbed from the stomach if you have a diet high in bran fiber.
Do not treat yourself for coughs, colds or allergies without asking your doctor or health care professional for advice. Some ingredients can increase possible side effects.
Where should I keep this medicine?
Keep out of the reach of children.
Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Protect from light and moisture. Throw away any unused medicine after the expiration date.
The occurrence of adverse drug reactions is common, owing to its narrow therapeutic index (the margin between effectiveness and toxicity). Adverse effects are concentration-dependent, and are rare when plasma digoxin concentration is <0.8 μg/l. They are also more common in patients with low potassium levels (hypokalemia), since digoxin normally competes with K+ ions for the same binding site on the Na+/K+ ATPase pump.
Common adverse effects (≥1% of patients) include loss of appetite, nausea, vomiting and diarrhea as gastrointestinal motility increases. Other common effects are blurred vision, visual disturbances (yellow-green halos and problems with color perception), confusion, drowsiness, dizziness, insomnia, nightmares, agitation, and depression, as well as a higher acute sense of sensual activities. Less frequent adverse effects (0.1%–1%) include: acute psychosis, delirium, amnesia, convulsions, shortened QRS complex, atrial or ventricular extrasystoles, paroxysmal atrial tachycardia with AV block, ventricular tachycardia or fibrillation, and heart block. Rarely, digoxin has been shown to cause thrombocytopenia. Gynaecomastia (enlargement of breast tissue) is mentioned in many textbooks as a side effect, thought to be due to the estrogen-like steroid moiety of the digoxin molecule, but when systematically sought, the evidence for this is equivocal. The pharmacological actions of digoxin usually result in electrocardiogram changes, including ST depression or T wave inversion, which do not indicate toxicity. PR interval prolongation, however, may be a sign of digoxin toxicity. Additionally, increased intracellular Ca2+ may cause a type of arrhythmia called bigeminy (coupled beats), eventually ventricular tachycardia or fibrillation. The combination of increased (atrial) arrhythmogenesis and inhibited atrioventricular conduction (for example paroxysmal atrial tachycardia with A-V block - so-called "PAT with block") is said to be pathognomonic (i.e. diagnostic) of digoxin toxicity.
An often described, but rarely seen, adverse effect of digoxin is a disturbance of color vision (mostly yellow and green) called xanthopsia. Vincent van Gogh's "Yellow Period" may have somehow been influenced by concurrent digitalis therapy. Other oculotoxic effects of digoxin include generalized blurry vision, as well as seeing a "halo" around each point of light. The latter effect can also be seen in van Gogh's Starry Night. Evidence of van Gogh's digoxin use is supported by multiple self portraits that include the foxglove plant, from which digoxin is obtained. (e.g. Portrait of Dr. Gachet)
Digoxin plasma concentrations may increase while on antimalarial medication hydroxychloroquine (based on two case reports from 1982).
In overdose, the usual supportive measures are needed. If arrhythmias prove troublesome, or malignant hyperkalaemia occurs (inexorably rising potassium level due to paralysis of the cell membrane-bound, ATPase-dependent Na/K pumps), the specific antidote is antidigoxin (antibody fragments against digoxin, trade names Digibind and Digifab). Toxicity can also be treated with higher than normal doses of potassium. Digoxin is not removed by hemodialysis or peritoneal dialysis with enough effectiveness to treat toxicity.
Digoxin has potentially dangerous interactions with verapamil, amiodarone, erythromycin, and epinephrine (as would be injected with a local anesthetic).
Mechanism of action
The mechanism of action is not completely understood; however, the current hypothesis is outlined below.
Digoxin binds to a site on the extracellular aspect of the α-subunit of the Na+/K+ ATPase pump in the membranes of heart cells (myocytes) and decreases its function. This causes an increase in the level of sodium ions in the myocytes, which leads to a rise in the level of intracellular calcium ions. This occurs because the sodium/calcium exchanger on the plasma membrane depends on a constant inward sodium gradient to pump out calcium. Digoxin decreases the sodium concentration gradient and the subsequent calcium outflow, thus raising the calcium concentration in myocardiocytes and pacemaker cells.
Increased intracellular calcium lengthens phase 4 and phase 0 of the cardiac action potential, which leads to a decrease in heart rate. Increased amounts of Ca2+ also leads to increased storage of calcium in the sarcoplasmic reticulum, causing a corresponding increase in the release of calcium during each action potential. This leads to increased contractility (the force of contraction) of the heart without increasing heart energy expenditure.
There is also evidence that digoxin increases vagal activity, thereby decreasing heart rate by slowing depolarization of pacemaker cells in the AV node. This negative chronotropic effect would therefore be synergistic with the direct effect on cardiac pacemaker cells. Digoxin is used widely in the treatment of various arrhythmias.
This article uses material from the Wikipedia article Digoxin, which is released under the Creative Commons Attribution-Share-Alike License 3.0.