Symmetrel Side Effects
Generic name: amantadine
Medically reviewed by Drugs.com. Last updated on Sep 30, 2020.
Note: This document contains side effect information about amantadine. Some of the dosage forms listed on this page may not apply to the brand name Symmetrel.
For the Consumer
Applies to amantadine: oral capsule, oral capsule extended release, oral capsule liquid filled, oral syrup, oral tablet, oral tablet extended release
Side effects requiring immediate medical attention
Along with its needed effects, amantadine (the active ingredient contained in Symmetrel) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking amantadine:
- Bladder pain
- bloody or cloudy urine
- blurred vision
- difficult, burning, or painful urination
- dizziness or lightheadedness
- frequent urge to urinate
- lower back or side pain
- seeing, hearing, or feeling things that are not there
- swelling of the hands, feet, or lower legs
- Inability to move the eyes
- increased blinking or spasms of the eyelid
- muscle spasm
- sticking out of the tongue
- troubled breathing, speaking, or swallowing
- uncontrolled twisting movements of the neck, trunk, arms, or legs
- unusual facial expressions
- decreased vision or any change in vision
- difficulty in coordination
- increased blood pressure
- increase in body movements
- irritation and swelling of the eye
- loss of memory
- mental depression
- severe mood or mental changes
- skin rash
- slurred speech
- sore throat
- thoughts of suicide or attempts at suicide
Side effects not requiring immediate medical attention
Some side effects of amantadine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- difficulty concentrating
- loss of appetite
- purplish red, net-like, or blotchy spots on the skin
- trouble with sleeping
- decrease in sexual desire
- dryness of the mouth, nose, and throat
- false sense of well-being
- unusual tiredness or weakness
For Healthcare Professionals
Applies to amantadine: compounding powder, oral capsule, oral capsule extended release, oral syrup, oral tablet, oral tablet extended release
Common (1% to 10%): Dizziness/lightheadedness, ataxia, headache, somnolence, dystonia
Uncommon (0.1% to 1%): Weakness, slurred speech, hyperkinesia
Rare (less than 0.1%): Convulsion
Frequency not reported: Falling asleep during activities of daily living, withdrawal-emergent hyperpyrexia (a syndrome resembling neuroleptic malignant syndrome)
Postmarketing reports: Coma, delirium, hypokinesia, involuntary muscle contractions, gait abnormalities, paresthesia, EEG changes, tremor[Ref]
Very common (10% or more): Hallucinations (up to 21%)
Common (1% to 10%): Insomnia, depression, anxiety, irritability, hallucinations, confusion, nervousness, abnormal dreams, agitation
Uncommon (0.1% to 1%): Psychosis, euphoria, abnormal thinking, amnesia
Rare (less than 0.1%): Suicide attempt, suicide, suicidal ideation
Very common (10% or more): Dry mouth (up to 16%); constipation (up to 13%)
Common (1% to 10%): Nausea, anorexia, diarrhea, decreased appetite
Uncommon (0.1% to 1%): Vomiting
Uncommon (0.1% to 1%): Congestive heart failure, hypertension
Common (1% to 10%): Dry eye, cataract, blurred vision
Uncommon (0.1% to 1%): Visual disturbance, punctate subeithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, optic nerve palsy
Rare (less than 0.1%): Oculogyric episodes
Very common (10% or more): Fall (up to 13%)
Common (1% to 10%): Fatigue, contusions
Frequency not reported: Death
Postmarketing reports: Fever[Ref]
Deaths have been reported from overdose with the lowest reported acute lethal dose as 1 gram. Drug overdose has resulted in cardiac, respiratory, renal, or CNS toxicity. Deaths have been reported in patients with renal impairment and attributed to drug accumulation.[Ref]
Common (1% to 10%): Dry nose, cough
Uncommon (0.1% to 1%): Dyspnea
Rare (less than 0.1%): Leukopenia, neutropenia
Common (1% to 10%): Livedo reticularis, pigmentation disorder
Uncommon (0.1% to 1%): Skin rash
Rare (less than 0.1%): Eczematoid dermatitis
Common (1% to 10%): Urinary tract infection, benign prostatic hyperplasia
Postmarketing reports: Elevated: CPK, BUN, serum creatinine[Ref]
Rare (less than 0.1%): Reversible liver enzyme elevations
Postmarketing reports: Elevated: alkaline phosphatase, LDH, bilirubin, GGT, SGOT, and SGPT[Ref]
Common (1% to 10%): Joint swelling, muscle spasms[Ref]
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2. "Product Information. Amantadine Hydrochloride (amantadine)." Sandoz Inc, Broomfield, CO.
3. "Product Information. Symmetrel (amantadine)." DuPont Pharmaceuticals, Wilmington, DE.
4. Smith EJ "Amantadine-induced psychosis in a young healthy patient." Am J Psychiatry 165 (2008): 1613
5. Michalski LS, Hantsch Bardsley C, Holt DR, Milner JE, Hou SH "Altered mental status in a transplant patient. Amantadine toxicity." Kidney Int 75 (2009): 243-4
6. Kataoka H, Ueno S "Dropped head associated with amantadine in Parkinson disease." Clin Neuropharmacol 34 (2011): 48-9
7. "Antiviral drugs for influenza." Med Lett Drugs Ther 51 (2009): 89-92
8. Beal E "Parkinson disease: Amantadine administration is associated with impulse control disorders in PD." Nat Rev Neurol 7 (2011): 62
9. Salgado JC, Gutknecht DR "A reticular rash." Am J Med 119 (2006): 577-8
10. Alonso Navarro H, Sanz-Aiz A, Izquierdo L, Jimenez Jimenez FJ "Syndrome of Inappropriate Antidiuretic Hormone Secretion Possibly Associated With Amantadine Therapy in Parkinson Disease." Clin Neuropharmacol 32 (2009): 167-168
Frequently asked questions
- How long does it take for amantadine to start working?
- Why should you not discontinue amantadine?
- Why was amantadine discontinued for flu?
- What symptoms does amantadine treat?
- What is Gocovri (amantadine) and how does it work?
- What is the difference between Osmolex ER and Gocovri?
- What is Gocovri used to treat?
More about Symmetrel (amantadine)
- During Pregnancy or Breastfeeding
- Dosage Information
- Drug Images
- Drug Interactions
- 3 Reviews
- Generic Availability
- Drug class: adamantane antivirals
Related treatment guides
Some side effects may not be reported. You may report them to the FDA.