Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
DRUG CLASS AND MECHANISM: Amiodarone is an oral and injectable drug
that is used to correct abnormal rhythms of the heart. (It is an antiarrhythmic
medication.) Although amiodarone has many side effects, some of which are severe
and potentially fatal, it has been successful in treating many arrhythmias when
other antiarrhythmic drugs have failed. Amiodarone is considered a "broad
spectrum" antiarrhythmic medication, that is, it has multiple and complex
effects on the electrical activity of the heart which is responsible for the
heart's rhythm. Among its most important electrical effects are:
a delay in
the rate at which the heart's electrical system "recharges" after the heart
contracts (repolarization);
a prolongation in the electrical phase during
which the heart's muscle cells are electrically stimulated (action potential);
a slowing of the speed of electrical conduction (how fast each individual
impulse is conducted through the heart's electrical system);
a reduction in
the rapidity of firing of the normal generator of electrical impulses in the
heart (the heart's pacemaker);
a slowing of conduction through various
specialized electrical pathways (called accessory pathways) which can be
responsible for arrhythmias.
In addition to being an antiarrhythmic medication,
amiodarone also causes blood vessels to dilate (enlarge). This effect can result
in a drop in blood pressure. Because of this effect, it also may be of benefit
in patients with congestive heart failure.
Amiodarone was discovered in 1961 and
approved by the FDA in December 1985.
STORAGE: Tablets and injection should be kept at room temperature,
20-25 C (68-77 F).
PRESCRIBED FOR: Amiodarone is approved for recurrent ventricular
fibrillation and hemodynamically unstable ventricular tachycardia.
DOSING: The
recommended dosing schedule is an initial loading dose of 800-1600 mg daily for
1 to 3 weeks, followed by 600-800 mg daily for 1 month, then 400 mg daily for
maintenance. Response should be closely monitored and dosing is individualized
for each patient. Amiodarone may be administered once daily or given twice daily
with meals to minimize stomach upset which is seen more frequently with higher
doses.
Amiodarone increases the blood levels of digoxin (Lanoxin) when the two drugs
are given together. It is recommended that the dose of digoxin be cut by 50%
when amiodarone therapy is started. Flecainide (Tambocor) blood concentrations
increase by more than 50% with amiodarone.
Procainamide (Procan-SR, Pronestyl)
and quinidine (Quinidex, Quinaglute) concentrations increase by 30%-50% during
the first week of amiodarone therapy. Additive electrical effects occurs with
these combinations, and worsening arrhythmias may occur as a result. Some
experts recommend that the doses of these other drugs be reduced when amiodarone
is started. Amiodarone can result in phenytoin (Dilantin) toxicity because it
causes a two- or three-fold increase in blood concentrations of phenytoin.
Symptoms of phenytoin toxicity including unsteady eye movement (temporary and
reversible), tiredness and unsteady gait.
Congestive heart failure (CHF) is a condition in which the heart's function as a pump is inadequate to meet the body's needs. A poor blood supply resulting from congestive heart failure may cause the body's organ systems to fail, leading to a weakened heart muscle and fluid accumulation in the lungs and body tissue. There are many diseases that can impair pumping efficiency and symptoms of congestive heart failure including fatigue, diminished exercise capacity, shortness of breath, and swelling. Treatments include lifestyle modifications, medications, heart transplant, and therapy.
Palpitations are unpleasant sensations of irregular and/or forceful beating of the heart. Palpitations can be relieved in many patients by stress reduction, stopping cigarettes, and reduction of caffeine and alcohol.
Premature ventricular contractions (PVCs) are premature heartbeats originating from the ventricles of the heart. PVCs are premature because they occur before the regular heartbeat. There are many causes of premature ventricular contractions to include: heart attack, high blood pressure, congestive heart failure, mitral valve prolapse, hypokalemia, hypoxia, medications, excess caffeine, drug abuse, and myocarditis.
Heart rhythm disorders vary from minor palpitations, premature atrial contractions (PACs), premature ventricular contractions (PVCs), sinus tachycardia, and sinus brachycardia, to abnormal heart rhythms such as tachycardia, ventricular fibrillation, ventricular flutter, atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), Wolf-White-Parkinson syndrome, brachycardia, or heart blocks. Treatment is dependant upon the type of heart rhythm disorder.
Palpitations are unpleasant sensations of irregular and/or forceful beating of the heart. Some persons with palpitations have no heart disease or abnormal heart rhythms and the reasons for their palpitations are unknown. In others, palpitations result from
abnormal heart rhythms (arrhythmias).
Arrhythmias refer to heartbeats that are too slow, too rapid, irregular, or too early.
Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias.
Slow arrhythmias (slower than 60 beats per minute) are called bradycardias.
Irregular heart rhythms are called fibrillations (as in
atrial fibrillation).
When a single heartbeat occurs earlier than normal, it is called a premature contraction, and this can cause the sensation of a forceful heartbeat.
Abnormalities in the atria, the ventricles, and the elect...
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