Blurred vision, nausea, loss of appetite, drowsiness, dizziness, lightheadedness, headache, dry mouth, constipation, or trouble sleeping may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.
Dizziness and lightheadedness can increase the risk of falling. Get up slowly when rising from a sitting or lying position.
To relieve dry mouth, suck (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute.
If you are taking the extended-release tablets, an empty tablet shell may appear in your stool. This effect is harmless because your body has already absorbed the medication.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: purplish-red blotchy spots on the skin (especially on the legs), swelling of the ankles/feet, difficulty urinating, vision changes, unusual strong urges (such as increased gambling, increased sexual urges, uncontrolled spending), mental/mood changes (such as anxiety, depression, hallucinations, suicidal thoughts/attempts), muscle spasms.
Get medical help right away if you have any very serious side effects, including: seizure.
Some people taking amantadine have fallen asleep suddenly during their usual daily activities (such as talking, driving). You might fall asleep without warning or without feeling drowsy. This effect can happen at any time even if you have used this medication for a long time. If you have increased sleepiness or fall asleep suddenly during the day, tell your doctor right away. Your risk is higher if you drink alcohol or take other medications that can make you drowsy. Do not drive or do other activities for which you need to be alert (see also Precautions section).
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.