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Osmolex ER

Generic name: amantadinea-MAN-ta-deen ]
Brand names: Gocovri, Osmolex ER
Drug class: Dopaminergic antiparkinsonism agents

Medically reviewed by on Aug 3, 2023. Written by Cerner Multum.

What is Osmolex ER?

Osmolex ER is used to treat Parkinson's disease and "Parkinson-like" symptoms such as stiffness or tremors, shaking, and repetitive uncontrolled muscle movements that may be caused by the use of certain drugs.

Osmolex ER is also used to treat or prevent influenza A in adults and children. This medicine may not be effective during every flu season because certain strains of the virus may be resistant to Osmolex ER. This medicine should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

Osmolex ER may also be used for purposes not listed in this medication guide.

Osmolex ER side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Osmolex ER may cause serious side effects. Call your doctor at once if you have:

You may have increased sexual urges, unusual urges to gamble, or other intense urges while taking this medicine. Talk with your doctor if this occurs.

Side effects may be more likely in older adults.

Common side effects of Osmolex ER may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


You should not use Osmolex ER if you received a nasal flu vaccine in the past 14 days.

Do not receive a nasal flu vaccine while taking Osmolex ER, and for at least 48 hours after your last dose. You may receive a flu shot (injection) while taking this medicine.

Before taking this medicine

You should not use Osmolex ER if you are allergic to it, or if:

Tell your doctor if you have ever had:

People with Parkinson's disease may have a higher risk of skin cancer (melanoma). Talk to your doctor about this risk and what skin symptoms to watch for.

It is not known whether Osmolex ER will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

You should not breast-feed while using this medicine.

Osmolex ER is not approved for influenza in a child younger than 1 year old. Gocovri is not approved for use by anyone younger than 18 years old.

How should I take Osmolex ER?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

If you take Osmolex ER to treat influenza A, start taking the medicine within 24 to 48 hours after flu symptoms begin. Keep taking this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared.

You may take Osmolex ER with or without food. You may need to take this medicine only at bedtime. Follow your doctor's instructions.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Swallow the capsule or tablet whole and do not crush, chew, or break it.

If you cannot swallow a capsule whole, open it and sprinkle the medicine into a spoonful of applesauce. Swallow the mixture right away without chewing. Do not save it for later use.

Call your doctor if your symptoms do not improve, or if you have a fever with a headache, cough, skin rash, or other new symptoms.

If you take Osmolex ER for Parkinson symptoms: You should not stop using this medicine suddenly or your condition may become worse. Stopping suddenly may also cause unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.

Store at room temperature away from moisture, heat, and light. Keep the bottle tightly closed when not in use.

What happens if I miss a dose?

Skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

Call your doctor if you miss several doses in a row.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of Osmolex ER can be fatal.

Overdose symptoms may include confusion, agitation, behavior changes, hallucinations, severe headache or pounding in your ears, muscle stiffness, problems with balance or walking, trouble breathing, fast heartbeats, or seizure.

What should I avoid while taking amantadine?

Do not receive a nasal flu vaccine while using Osmolex ER, and for at least 48 hours after your last dose. The vaccine may not work as well during this time, and may not protect you from influenza.

Do not drink alcohol. Dangerous side effects could occur.

Avoid driving or operating machinery until you know how Osmolex ER will affect you. Osmolex ER may impair your thinking or reactions. Some people taking this medicine have fallen asleep during normal daytime activities such as working, talking, eating, or driving. You may fall asleep suddenly, even after feeling alert. Be careful if you drive or do anything that requires you to be alert.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Avoid taking diet pills, caffeine pills, or other stimulants (such as ADHD medications) without your doctor's advice. Taking a stimulant together with Osmolex ER can increase your risk of unpleasant side effects.

What other drugs will affect Osmolex ER?

Using Osmolex ER with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Tell your doctor about all your other medicines, especially:

This list is not complete. Other drugs may affect Osmolex ER, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Popular FAQ

The main differences between Gocovri and Osmolex ER center around their approved uses, dosage forms, strength and study designs for FDA approval. Approval of Gocovri was based on placebo-controlled clinical studies in patients with Parkinson's disease with levodopa-induced dyskinesias, whereas the effectiveness of Osmolex ER was based upon bioavailability studies that compared Osmolex ER to immediate-release amantadine. Gocovri and Osmolex ER are not interchangeable with other amantadine immediate- or extended-release products. Continue reading

Gocovri (amantadine) is used for the treatment of dyskinesia in patients with Parkinson's disease receiving levodopa-based therapy, with or without concomitant dopaminergic medication. It is also used as an add-on therapy in Parkinson's patients who are being treated with levodopa/carbidopa and who are experiencing "off" episodes. Continue reading

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.