Amantadine Side Effects

Not all side effects for amantadine may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to amantadine: oral capsule, oral capsule liquid filled, oral solution, oral syrup, oral tablet

Along with its needed effects, amantadine 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:

Less common
  • Blurred vision
  • confusion
  • difficult urination
  • dizziness or lightheadedness
  • fainting
  • seeing, hearing, or feeling things that are not there
  • swelling of the hands, feet, or lower legs
Rare
  • Convulsions (seizures)
  • decreased vision or any change in vision
  • difficulty in coordination
  • fever, chills, or sore throat
  • 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
  • thoughts of suicide or attempts at suicide
  • unexplained shortness of breath

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:

More common
  • Agitation, anxiety, or nervousness
  • difficulty concentrating
  • headache
  • irritability
  • loss of appetite
  • nausea
  • purplish red, net-like, or blotchy spots on the skin
  • trouble in sleeping or nightmares
Less common or rare
  • Constipation
  • decrease in sexual desire
  • diarrhea
  • drowsiness
  • dryness of the mouth, nose, and throat
  • false sense of well-being
  • vomiting
  • unusual tiredness or weakness

For Healthcare Professionals

Applies to amantadine: compounding powder, oral capsule, oral syrup, oral tablet

General

The adverse effects of amantadine are generally mild and, when they occur, may diminish or cease after a week or more on the medication. The most commonly reported side effects have included nausea, dizziness/lightheadedness, and insomnia in 5% to 10% of patients. All side effects, particularly those involving the central nervous system, may be more likely and more severe in patients with renal dysfunction and/or advanced age. Close monitoring for undue adverse effects is highly recommended.

Nervous system

Nervous system side effects have included dizziness/lightheadedness and insomnia in 5% to 10% of patients. Hallucinations, confusion, ataxia, headache, somnolence, agitation, and fatigue have been reported in 1% to 5% of patients. Weakness, slurred speech, and hyperkinesia have been reported in 0.1% to 1% of patients and instances of convulsion have been reported in less than 0.1% of patients. At least one case of dropped head syndrome (associated with unbalanced contraction of the neck muscles) has been reported. Neuroleptic malignant syndrome, involuntary muscle contractions, coma, stupor, hypokinesia, hypertonia, gait abnormalities, paresthesia, EEG changes, and tremor have been reported during postmarketing experience. Agitation, hallucinations, stupor, and slurred speech have also occurred after abrupt discontinuation.

Most cases of CNS toxicity have occurred in patients with renal insufficiency, seizure disorders, or psychiatric illnesses, and in elderly patients receiving 200 mg/day for influenza prophylaxis.

Psychiatric

A case report describes a psychotic episode consisting of abnormal behavior in a young woman following a week of concomitant therapy with Naldecon. The patient had no personal or family history of psychiatric illness and no history of recreational substance use. It is not clear whether the episode was due to the amantadine, the phenylpropanolamine in the Naldecon, or an interaction between the two.

An exacerbation of panic occurred in one patient approximately 2 weeks after the initiation of amantadine therapy for Parkinson's disease. The causal relationship is unclear.

Severe CNS adverse effects have most often been associated with dosages greater than approximately 2 mg/kg/day and/or amantadine blood levels exceeding 1 mcg/mL. Most cases of CNS toxicity have occurred in patients with renal insufficiency, seizure disorders, or psychiatric illnesses, and in elderly patients receiving 200 mg/day for influenza prophylaxis.

Psychiatric side effects have included depression, anxiety, irritability, nervousness, and dream abnormality in 1% to 5% of patients. Psychosis, euphoria, thinking abnormality, amnesia, and decreased libido have been reported in 0.1% to 1% of patients and suicidal attempt, suicidal ideation, and suicide have been reported in less than 0.1% of patients. Aggressive behavior, delirium, delusions, manic reaction, paranoid reaction, delusions of parasitosis, pathological gambling, increased libido (including hypersexuality), and impulse control symptoms have been reported during postmarketing experience. Delirium, delusions, paranoid reaction, anxiety, and depression have also occurred after abrupt discontinuation.

Gastrointestinal

Gastrointestinal side effects have included nausea in 5% to 10% of patients; diarrhea, constipation, anorexia, and dry mouth in 1% to 5% of patients; and vomiting in 0.1% to 1% of patients. Dysphasia has been reported during postmarketing experience.

Cardiovascular

Cardiovascular side effects have included orthostatic hypotension in 1% to 5% of patients, and congestive heart failure and hypertension in 0.1% to 1% of patients. Cardiac arrest, arrhythmias (including malignant arrhythmias), hypotension, and tachycardia have been reported during postmarketing experience.

Congestive heart failure with severe lower limb edema was diagnosed in one patient receiving amantadine, but resolved following drug discontinuation. A positive correlation with amantadine therapy could not be established, although no other cause for this patient's heart failure was found.

Ocular

Ocular side effects have included visual disturbance, including punctuate subepithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, and optic nerve palsy in 0.1% to 1% of patients and oculogyric episodes in less than 0.1% of patients. Keratitis and mydriasis have been reported during postmarketing experience.

At least two cases of decreased visual acuity have been reported following approximately three weeks of amantadine therapy. Both resolved after drug discontinuation. In one case, the visual disturbance was related to a corneal edema similar to that seen with amiodarone.

Other

Other side effects have included peripheral edema (1% to 5%). Edema and fever have been reported during postmarketing experience.

Respiratory

Respiratory side effects have included dry nose (1% to 5%) and dyspnea (0.1% to 1%). Acute respiratory failure, pulmonary edema, and tachypnea have been reported during postmarketing experience.

Hematologic

Hematologic side effects have included leukopenia and neutropenia in less than 0.1% of patients. Leukocytosis and agranulocytosis have been reported during postmarketing experience.

Dermatologic

Livedo reticularis occurs mainly on the legs. It is generally reversible over weeks to months following drug discontinuation.

Dermatologic side effects have included livedo reticularis (1% to 5%), skin rash (0.1% to 1%), and eczematoid dermatitis (less than 0.1%). Pruritus and diaphoresis have been reported during postmarketing experience.

Hypersensitivity

Hypersensitivity side effects have included allergic reactions including anaphylactic reactions during postmarketing experience.

Genitourinary

Genitourinary side effects have included urinary retention (0.1% to 1%).

Renal

Renal side effects have included elevations in BUN and serum creatinine during postmarketing experience.

Hepatic

Hepatic side effects have included elevations in bilirubin, GGT, SGOT, and SGPT during postmarketing experience.

Metabolic

Metabolic side effects have included elevated alkaline phosphatase and lactate dehydrogenase during postmarketing experience.

Musculoskeletal

Musculoskeletal side effects have included elevated creatine kinase during postmarketing experience.

Endocrine

A 66-year-old female patient with Parkinson disease developed syndrome of inappropriate antidiuretic hormone secretion nine days after starting amantadine and entacapone. The patient did not recover following discontinuation of entacapone. Five days after entacapone was stopped, amantadine was discontinued. The patient gradually improved following amantadine discontinuation.

Endocrine side effects have included at least one case of syndrome of inappropriate antidiuretic hormone secretion.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.

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