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Generic Name: Digoxin
Brand Name(s):
Information updated: April 1, 2000
Overview
digoxin Other Brand Names: Lanoxin DATE: 04/01/2000 12:00:00Overview
Lanoxin is among the most frequently prescribed drugs in this country.
It is a digitalis heart medicine that to this day is derived from the
leaves of a plant related to foxglove. Digitalis has been used medically for
over 200 years.
Lanoxin is prescribed for congestive heart failure and
certain irregular heart rhythms, or arrhythmias.
People with heart
failure often experience fluid retention, sensitivity to cold, fatigue and
difficulty breathing after mild exercise, and a nighttime cough, especially when
they lie down.
Lanoxin works partly by increasing the pumping power of
the heart. It can also help slow an abnormal heart when atrial rhythms gets out
of control. But Lanoxin is complex to manage, especially in older people.
This medication requires careful monitoring to prevent an overdose as
the therapeutic level is very close to the toxic dose. Periodic blood tests are
crucial.
Side Effects and Interactions
Signs of igitalis toxicity include loss of
appetite, nausea, diarrhea, vomiting, stomach pain, blurred or disturbed color
vision, headache, drowsiness, fatigue, and muscle weakness.
If any of
these symptoms occur, contact your physician immediately.
Other adverse
reactions may include personality change, depression, confusion, disorientation,
apathy, bad dreams and hallucinations. Any side effects should be brought to a
doctor's attention promptly.
Lanoxin can interact with a wide range of
over-the-counter and prescription medications. Antacids, for example, may
diminish the proper absorption of digoxin.
So can certain diarrhea
medicines and drugs to control cholesterol like Questran, Cholybar or Colestid.
A number of other medications, such as Cordarone, Rhythmol and quinidine
drugs, may make Lanoxin more toxic.
So can Sandimmune, used to prevent
transplant rejection.
Calcium-blocking blood pressure medicines like
Procardia, Cardizem CD
or Calan SR
may also increase digoxin levels dangerously.
Diuretics like Lasix
are often prescribed in conjunction with Lanoxin. A patient taking both
medicines should be monitored carefully, however, as the diuretic may make the
body lose too much potassium or magnesium. This could lead to serious changes in
heart rhythm.
Potassium-sparing diuretics such as Aldactazide or
Moduretic could make monitoring and interpreting tests far more
complicated.
One of the trickiest interactions is that of Lanoxin with
erythromycin and tetracycline. For reasons that are not well understood, about
one person in ten harbors bacteria in the gut that metabolizes digoxin. If this
intestinal flora is wiped out with an antibiotic, the person may suddenly be
exposed to much more Lanoxin than usual, even though they may still be
swallowing the exact same dose.
Because of these possible complications,
never add any other prescription or over-the-counter medications to Lanoxin
without first checking with your pharmacist and physician.
Extracts of
the herb hawthorn
may increase the activity (but not necessarily the toxicity) of cardiac tonics
such as digitalis.
Hawthorn is not recommended for people who are taking
Lanoxin or other digoxin medications.
Licorice
can greatly increase potassium loss when taking medicines such as Lanoxin;
severe potassium loss greatly increases the risk of heart rhythm irregularities
in people taking Lanoxin.
The herb cascara_sagrada taken with Lanoxin
also could result in excessive potassium loss
with resulting heart rhythm irregularities.
The herb St. John's wort can speed elimination of digoxin from the body, which could
reduce its effectiveness.
Psyllium
can affect the absorption of Lanoxin; if you take it, it is best to do so at
least an hour after taking Lanoxin.
The herb ma huang is incompatible with cardiac glycosides such as Lanoxin; serious
disruption of heart rhythm may occur.
Never stop taking Lanoxin or switch
to another brand of digoxin unless your physician is monitoring closely. Because
the effective dose is so close to the toxic dose, this might be dangerous.
Special Precautions
People with reduced kidney function generally require less Lanoxin. As people age their kidneys may no longer process this medicine as efficiently. This is another reason why periodic blood tests for digoxin levels are essential.
It is also crucial to monitor both potassium and magnesium levels. If these essential minerals become depleted because of diuretic therapy, Lanoxin can become extremely dangerous. Blood tests are the only way to determine electrolyte levels.
Taking the Medicine
It is usually recommended that Lanoxin be taken at the same time and in the same way each day.
For many people the most convenient time is with breakfast. However, food high in bran may
reduce the absorption of this drug.
If your breakfast tends to be high in such foods, you
might want to schedule your Lanoxin for another time of day.
Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Their syndicated radio show can be heard on public radio.
© 2000