Brand name:
AMIODARONE - ORAL (am-ee-OH-duh-rown)
GENERIC NAME: amiodarone
BRAND NAME: Cordarone
DRUG CLASS AND MECHANISM: Amiodarone is used to correct abnormal rhythms
of the heart (an antiarrhythmic medication). Amiodarone was discovered
in 1961. Amiodarone was approved by the FDA for clinical use as an antiarrhythmic
agent in December of 1985. Although amiodarone has many side effects,
some of which are severe and potentially fatal, it has been successful
in treating many arrhythmias where other antiarrhythmics fail. 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:
1. a delay in the rate at which the heart's electrical system "recharges" after
the heart contracts (repolarization);
2. a prolongation in the electrical phase during which the heart's muscle cells
are electrically stimulated (action potential);
3. a slowing of the speed of electrical conduction (how fast each individual
impulse is conducted through the heart's electrical system);
4. a reduction in the rapidity of firing of the normal generator of electrical
impulses in the heart (the heart's pacemaker);
5. 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.
PRESCRIPTION: yes
GENERIC AVAILABLE: yes
PREPARATIONS: Tablets (pink), round in shape: 200mg.
STORAGE: Tablets should be kept at room temperature, less than 30°C
(86°F).
PRESCRIBED FOR: Amiodarone is used for many serious arrhythmias of the
heart including ventricular fibrillation, ventricular tachycardia, atrial
fibrillation, and atrial flutter.
DOSING: Amiodarone usually is given in several daily doses to minimize
stomach upset which is seen more frequently with higher doses. For this
same reason, it is also recommended that amiodarone be taken with meals.
DRUG INTERACTIONS: Amiodarone may interact with beta- blockers such
as atenolol (Tenormin), propranolol (Inderal), metoprolol (Lopressor),
or certain calcium-channel blockers, such as verapamil (Calan, Isoptin,
Verelan, Covera-HS) or diltiazem (Cardizem, Dilacor, Tiazac), resulting
in an excessively slow heart rate or a block in the conduction of the
electrical impulse through the heart.
Amiodarone increases the blood levels of digoxin (Lanoxin) when the
two drugs are given together. It is recommended that the dose of digoxin
is 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.
Ritonavir (Norvir) can inhibit the enzyme that is responsible for the
metabolism of amiodarone. Although no clinical problems have been recognized
as a result of this interaction yet, it would be prudent to avoid this
combination for fear of the potential for amiodarone toxicity.
Amiodarone also can interact with tricyclic antidepressants (e.g. amitriptyline,
Elavil), or phenothiazines (e.g. chlorpromazine, Thorazine) and potentially
cause serious arrhythmias.
Amiodarone interacts with warfarin (Coumadin) and increases the risk
of bleeding. The bleeding can be serious or even fatal. This effect can
occur as early as 4-6 days after the start of the combination of drugs
or can be delayed by a few weeks.
