Amantadine (Symmetrel)

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What Is Amantadine (Symmetrel)?

Amantadine is the generic form of the brand-name drug Symmetrel, which is used to treat and prevent respiratory infections caused by the influenza A virus.
It can also treat symptoms of Parkinson's disease, such as stiffness and shaking, and conditions that are similar to Parkinson's disease.
Amantadine was initially used to prevent influenza A during flu season. Later, doctors discovered its benefits for treating symptoms of Parkinson's disease.
According to the Centers for Disease Control and Prevention (CDC), this medication should not be used by itself to treat or prevent influenza A because one strain of this virus in the United States and Canada is resistant to the medication.
Amantadine is an antiviral drug that is believed to work by stopping the growth of a virus. It helps treat the symptoms of Parkinson's disease by increasing the effects of dopamine. Dopamine is a neurotransmitter in the brain; people with Parkinson's disease typically have low levels of dopamine.
Amantadine comes in a capsule and liquid form to be taken by mouth.

Amantadine Warnings

Amantadine should not be used as a substitute for a flu vaccine and it should not be used with the flu vaccine that is inhaled through the nose because a serious interaction may occur.
This medicine may cause some people to become irritable, agitated, or display other abnormal behaviors. It may also cause suicidal thoughts or tendencies in some patients.
Before taking amantadine, tell your doctor if you have or have ever had:
  • Epilepsy or any other type of seizures
  • Heart disease
  • Heart failure
  • Kidney disease
  • Liver disease
  • Low blood pressure
  • Recurring skin rash
  • Mental illness
  • Untreated closed-angle glaucoma (a type of eye disease)
You should not take more or less of amantadine than your doctor prescribes. Don't stop taking this drug without first talking with your doctor.
In patients with Parkinson's disease, the effects of amantadine may not be noticed for several weeks. If this medicine causes insomnia, take your last dose several hours before bedtime.

Pregnancy and Amantadine

There are no well-controlled studies to evaluate amantadine's safety in pregnancy, so the risks and benefits should be taken into consideration to determine if this medication should be used in pregnant women.
Amantadine is excreted into human breast milk in low concentrations. The manufacturer recommends that this drug should be used cautiously in nursing mothers.

Amantadine (Symmetrel) Side Effects

Common Side Effects of Amantadine:

Tell your doctor if you experience any of the following common side effects.
  • Blurred vision
  • Lightheadedness
  • Trouble sleeping
  • Dizziness
  • Feeling as if you are going to faint

Serious Side Effects of Amantadine:

Call your doctor immediately if you experience any of the following serious side effects.
  • Swelling of the hands, legs, or feet
  • Shortness of breath
  • Depression or anxiety
  • Difficulty urinating
  • Rash

Amantadine (Symmetrel) Interactions

Amantadine and Alcohol

Drinking alcoholic beverages while taking amantadine may cause issues such as circulation problems, dizziness, lightheadedness, fainting, or confusion. Don't drink alcohol while you are taking this medicine.

Amantadine and Drug Interactions

Tell your doctor about all prescription, non-prescription, illicit, recreational, herbal, nutritional, or dietary drugs you are taking, especially:
  • Benztropine (Cogentin)
  • Hydrochlorothiazide with triamterene (Maxzide, Dyazide)
  • Drugs for depression
  • Other drugs for Parkinson's disease
  • Drugs for spasms of the stomach or intestines
  • Stimulants
  • Trihexyphenidyl (Artane)
  • Vitamins

Amantadine and Other Interactions

Amantadine may cause blurred vision. Be careful when driving or performing activities that require alertness.

Amantadine (Symmetrel) Dosage

You should follow your doctor's orders or the directions on the prescription label when taking amantadine. The following are average doses of this medicine for oral dosage forms (capsules, syrup, and tablets):

For treatment or prevention of flu:

  • Adults and teens: 200 milligrams (mg) or four teaspoons, once a day as a single dose.
  • Older adults: 100 mg, once a day as a single dose.
  • Children ages 9 to 12: 100 mg or two teaspoons, two times a day.
  • Children ages 1 to 9: Dose is based on body weight and must be determined by your doctor. The usual dose is 4.4 to 8.8 mg per kilogram (kg) of body weight per day. The dose is divided evenly and given two times a day. However, the dose is usually not more than 150 mg per day.
  • Children up to 1 year of age: Use and dose must be determined by your doctor.

For treatment of Parkinson's disease or movement conditions:

  • Adults: 100 mg, two times a day. Your doctor may adjust your dose.
  • Older adults: Begin with 100 mg, once a day, as a single dose. Your doctor may adjust your dose.
  • Children: Use and dose must be determined by the doctor.
Amantadine may cause an upset stomach. You should take this medication with food or milk to avoid this side effect.

Amantadine Overdose

Contact a poison control center or emergency room immediately if you suspect an overdose. You can get in touch with a poison control center at (800) 222-1222.

Missed Dose of Amantadine

If you miss a dose of amantadine, take it as soon as you remember. If it is almost time for the next dose, skip the missed dose and continue on your regular medication schedule. Don't "double up" to make up for a missed one.

Amantadine Pictures

Amantadine 100 mg-UDL, yellow, capsule,
Amantadine 100 mg-APH, red, capsule,
Amantadine 100 mg-UPS, yellow, capsule,
Amantadine 100 mg-GG, red, capsule,