GENERIC NAME: amantadine
BRAND NAME: Symmetrel
DRUG CLASS AND MECHANISM: Amantadine is a synthetic (man-made)
anti-viral drug that can inhibit the replication of viruses
in cells. To prevent a viral infection, the drug should
be present before exposure to the virus. Clearly, this
is not practical for most viral infections. It was initially
used to prevent influenza A during flu season, and, if
given within 24 to 48 hours of the onset of flu symptoms,
to decrease the severity of the flu. Later amantadine
was found to cause improvement in the symptoms of Parkinson's
disease. Amantadine's mechanism of action in Parkinson's
disease is not fully understood. Its effects may be related
to its ability to augment (amplify) the effects of dopamine,
a neurotransmitter in the brain, that is reduced in Parkinson's
disease. Amantadine is less effective than levodopa in
Parkinson's disease but can offer additional benefit when
taken with levodopa. Amantadine was approved by the FDA
in 1966.
GENERIC AVAILABLE: yes
PRESCRIPTION: yes
PREPARATIONS: Amantadine is available as 100mg soft
gelatin capsules and as a syrup containing 50mg per
each teaspoon.
STORAGE: Store at room temperature between 15 and 30＜C
(59 and 86＜F).
PRESCRIBED FOR: Amantadine is used for the prevention
or treatment of infections with influenza A virus, especially
for individuals at high-risk such as immunosuppressed
patients and nursing home residents. It should not be
used as a substitute for vaccination. Amantadine also
is used for control of the symptoms of Parkinson's disease.
DOSING: Amantadine is taken once or twice daily with
or without food. If it causes an upset stomach, it can
be taken with food.
For treatment of influenza, amantadine should be started
within 24 to 48 hours after the onset of signs or symptoms
and should be continued for 24 to 48 hours after the
disappearance of signs or symptoms. To prevent influenza,
amantadine should be started as soon as possible after
exposure to the influenza virus and continued for at
least 10 days.
Persons with reduced kidney function and elderly persons
may need lower doses (or less frequent doses).
DRUG INTERACTIONS: Amantadine adds to the sedating
effects alcohol and other sedating drugs such as the
benzodiazepine class of anti-anxiety drugs (e.g., Valium,
Ativan, Klonopin, Xanax, Ambien), the tricyclic class
of antidepressants (e.g., Elavil, Tofranil, Norpramin),
dicyclomine (Bentyl), certain antihistamines (Benadryl,
Vistaril, Atarax, Tavist), opiate agonists (e.g., Dilaudid;
Vicodin; Percocet; Codeine) and certain antihypertensive
medications (e.g., Catapres, Inderal). Such combinations
can cause dizziness, confusion, lightheadedness, fainting,
or dizziness upon standing.
Since amantadine amplifies the actions of dopamine
in the brain, drugs which block the effects of dopamine
should be avoided in persons taking amantadine when
amantadine is used for the treatment of Parkinson's
disease. Such drugs include haloperidol (Haldol), metoclopramide
(Reglan), and phenothiazines, e.g., thioridazine (Mellaril)
or triflupromazine (Stelazine).
The use of the diuretics hydrochlorothiazide or triamterene
(Dyazide; Maxzide) with amantadine can reduce the kidney's
ability to eliminate amantadine. This can lead to high
levels of amantadine in the blood and amantadine-associated
toxicity.
PREGNANCY: No well-controlled studies have been done
in pregnant women to evaluate amantadine's safety. Physicians
may choose to use amantadine during pregnancy when the
potential benefits outweigh the potential but unknown
risks to the fetus.
NURSING MOTHERS: Amantadine is excreted into breast
milk in low concentrations. Although no information
is available on the effects in infants, the manufacturer
recommends that amantadine be used cautiously in nursing
mothers.
SIDE EFFECTS: The most frequent side effects associated
with amantadine include dizziness, loss of coordination,
inability to sleep, and nervousness, nausea, and vomiting.
All of these side effects have been reported to occur
in about 1 in 20 persons. Effects can appear after a
few hours or several days of therapy. Less common side
effects include headache, irritability, nightmares,
depression, confusion, drowsiness, and hallucinations,
weakness, amnesia, slurred speech, diarrhea, constipation,
and loss of appetite, and discolorations in the eye.
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