Neurological
Side effects include drowsiness (especially while driving), lightheadedness, falls, and dizziness. Patients on amantadine should avoid combination with other central nervous system (CNS) depressing agents, such as alcohol. Excessive alcohol usage may increase the potential for CNS effects such as dizziness, confusion, and light headedness.Rare severe adverse effects include neuroleptic malignant syndrome, depression, convulsions, psychosis, and suicidal ideation. It has also been associated with disinhibited actions (gambling, sexual activity, spending, other addictions) and diminished control over compulsions. Cardiovascular
Amantadine may cause orthostatic hypotension, syncope, and peripheral edema. Gastrointestinal
Amantadine has also been associated with dry mouth and constipation. Skin
Rare cases of skin rashes, such as Stevens–Johnson syndrome and livedo reticularis have also been reported in patients treated with amantadine. Pregnancy and lactation
Amantadine is Food and Drug Administration category C for pregnancy. Teratogenic effects have been observed in humans (case reports) and animal reproduction studies. Amantadine may also be present in breast milk and negatively alter breast milk production or excretion. The decision to breastfeed during amantadine therapy should consider the risk of infant exposure, the benefits of breastfeeding, and the benefits of the drug to the mother. Interactions
Amantadine may affect the central nervous system due to dopaminergic and anticholinergic properties. The mechanisms of action are not fully known. Because of the CNS effects, caution is required when prescribing additional CNS stimulants or anticholinergic drugs. Thus, concurrent use of alcohol with Amantadine is not recommended due to enhanced CNS depressant effects. In addition, anti-dopaminergic drugs such as metoclopramide and typical anti-psychotics should be avoided.
The extended release amantadine formulation is commonly used to treat dyskinesias in people receiving levodopa therapy for Parkinsons disease. A 2003 Cochrane review had concluded there was insufficient evidence to prove the safety or efficacy of amantadine to treat dyskinesia.In 2008, the World Health Organization reported amantadine is not effective as a stand-alone parkinsonian therapy, but recommended it could be used in combination therapy with levodopa. Influenza A
Amantadine is not recommended for treatment or prophylaxis of influenza A in the United States. Amantadine has no effect preventing or treating influenza B infections. The US Centers for Disease Control and Prevention found 100% of seasonal H3N2 and 2009 pandemic flu samples were resistant to adamantanes (amantadine and rimantadine) during the 2008–2009 flu season.The U.S. Centers for Disease Control and Prevention (CDC) guidelines recommend only neuraminidase inhibitors for influenza treatment and prophylaxis. The CDC recommends against amantadine and rimantadine to treat influenza A infections.Similarly, the 2011 World Health Organization (WHO) virology report showed all tested H1N1 influenza A viruses were resistant to amantadine. WHO guidelines recommend against use of M2 inhibitors for influenza A. The continued high rate of resistance observed in laboratory testing of influenza A has reduced the priority of M2 resistance testing.A 2014 Cochrane review did not find evidence for efficacy or safety of amantadine used for the prevention or treatment of influenza A.

Extra-pyramidal side effects
An extended release formulation is used to treat levodopa-induced dyskinesia in patients with Parkinsons disease.