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Osmolex ER

amantadine
Used for Parkinson's Disease
Used for Parkinson's Disease

Osmolex ER (amantadine) is an NMDA antagonist. It's taken by adults to treat Parkinson’s disease (PD) and extrapyramidal symptoms (movement-related side effects) caused by medications. Osmolex ER (amantadine) is taken by mouth once a day in the morning. Common side effects include nausea, dizziness, lightheadedness, and trouble sleeping.

Reviewed by:
reviewer
Ally Tsai, PharmD
reviewer
Connie Zheng, PharmD
Last reviewed on January 9, 2024
BasicsSide effectsPros & consPharmacist tipsFAQsWarningsDosageInteractionsCostContraindicationsAlternativesReferencesPricesMedicare
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What is Osmolex ER (amantadine)?

What is Osmolex ER (amantadine) used for?

How Osmolex ER (amantadine) works

Osmolex ER (amantadine) is an N-methyl-D-aspartate (NMDA) antagonist. The way it treats Parkinson's disease isn't well-understood. But it's thought to work by blocking NMDA receptor in the brain, which raises dopamine levels. This helps to relieve some movement symptoms, such as trembling, stiffness, and slowness of movement.

Are you looking for information on amantadine immediate-release or Gocovri (amantadine) extended-release capsule instead?

Drug Facts

Common BrandsOsmolex ER
Drug ClassNMDA antagonist
Controlled Substance ClassificationNot a controlled medication
Generic StatusNo lower-cost generic available
AvailabilityPrescription only
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$634.71(save 28.44%)
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$454.20
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What are the side effects of Osmolex ER (amantadine)?

The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.

Common Side Effects

Please note: These are common side effects reported by people who took amantadine immediate-release.
  • Nausea (5-10%)
  • Dizziness (5-10%)
  • Trouble sleeping (5-10%)

Other Side Effects

  • Depression, anxiety
  • Feeling irritated, agitated, or confused
  • Hallucinations
  • Strange dreams
  • Not feeling hungry
  • Dry mouth or dry nose
  • Constipation or diarrhea
  • Feeling tired
  • Headache
  • Livedo reticularis (web-like purple-blue skin discoloration)

Serious Side Effects

Contact your healthcare provider immediately if you experience any of the following.
  • Suicidal thoughts or behaviors
  • Neuroleptic malignant syndrome (NMS): very high fevers, irregular pulse, sweating, muscle stiffness, confusion, changes in blood pressure
  • Accidentally taking too much (overdose): death, fast heartbeat, difficulty breathing, decreased urination, stiff or rigid arms or legs, confusion

Source: DailyMed

The following side effects have also been reported

Along with its needed effects, a medicine 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:

More common

Bladder pain

bloody or cloudy urine

blurred vision

confusion

difficult, burning, or painful urination

dizziness or lightheadedness

fainting

falls

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

Less common

Inability to move the eyes

increased blinking or spasms of the eyelid

muscle spasm

sticking out of the tongue

trouble breathing, speaking, or swallowing

uncontrolled twisting movements of the neck, trunk, arms, or legs

unusual facial expressions

Rare

Chills

decreased vision or any change in vision

difficulty in coordination

fever

increased blood pressure

increase in body movements

irritation and swelling of the eye

loss of memory

mental depression

seizures

severe mood or mental changes

skin rash

slurred speech

sore throat

thoughts of suicide or attempts at suicide

Some side effects 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

difficulty concentrating

dry mouth

headache

irritability

loss of appetite

nausea

nervousness

nightmares

purplish red, net-like, or blotchy spots on the skin

trouble with sleeping

Less common

Blindness

blurred vision

constipation

decrease in sexual desire

decreased vision

diarrhea

drowsiness

dry eyes

dryness of the mouth, nose, and throat

false sense of well-being

joint swelling

unusual tiredness or weakness

vomiting

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

pros-and-cons

Pros and cons of Osmolex ER (amantadine)

thumbs-up

Pros

Only taken once a day

Can be taken with or without food

Delivers medication consistently throughout the day

thumbs-down

Cons

Not safe for use in end-stage kidney disease

Can cause daytime sleepiness during normal activities

Can cause fainting due to sudden drop in blood pressure

pharmacist-tips

Pharmacist tips for Osmolex ER (amantadine)

pharmacist

  • Amantadine has different formulations, including Osmolex ER (amantadine). Each formulation has different directions. If you're just starting or switching to a different formulation of amantadine, double check with your provider that the formulation, dose, and directions are appropriate.

    • Osmolex ER (amantadine) should be swallowed whole. Don't chew or crush the tablets.

      • You might see the tablet shell for Osmolex ER (amantadine) in your stool. This is a common side effect since the tablet shell doesn't dissolve completely even after the medication is absorbed by your body.

        • Osmolex ER (amantadine) can cause you to fall asleep during normal activities, even if you aren't drowsy. Don't drive a car or operate machinery until you know how this medication affects you. Avoid drinking alcohol while taking Osmolex ER (amantadine) because it can worsen sleepiness. Make sure to take this medication at bedtime to lessen this side effect.

          • Osmolex ER (amantadine) can also cause blurry vision and sudden dizziness. Get up slowly from a sitting or lying down position to prevent a sudden drop in blood pressure.

            • Let your provider know right away if you experience symptoms of depression or worsening mood while taking Osmolex ER (amantadine).

              • Let your provider know if you've unusual urges, such as gambling, binge eating, compulsive shopping, and stronger sexual drive. These behaviors can be serious side effects from taking Osmolex ER (amantadine).

                • If you're pregnant or breastfeeding, speak to your provider before taking Osmolex ER (amantadine). According to animal studies, Osmolex ER (amantadine) might cause harm to unborn babies. This medication is also passed into breast milk, but it's not clear how it can affect breastfed babies.

                  • If you want to stop Osmolex ER (amantadine), talk with your provider. Don't stop taking this medication suddenly since this can raise your risk for side effects. Your provider can help you stop this medication safely by lowering your dose slowly over time.

                    • Check in with your provider to see if you are up-to-date on your vaccines before starting Osmolex ER (amantadine). You won't be able to receive live vaccines, such as Varivax (varicella vaccine), during treatment with this medication. This is because Osmolex ER (amantadine) can cause live vaccines to not work as well.

                      • Don't take more Osmolex ER (amantadine) than what your provider prescribed. Taking too much of this medication can be dangerous and even lead to death. If you miss a dose of Osmolex ER (amantadine), don't take an extra dose. Skip the missed dose and take your next dose at the scheduled time.

                        • Osmolex ER (amantadine) can interact with many medications. For example, sodium bicarbonate can cause Osmolex ER (amantadine) to build up in your body. This leads to overdose of Osmolex ER (amantadine), which can be dangerous. Let your provider or pharmacist know what medications you're taking, including over-the-counter products and supplements, before you start Osmolex ER (amantadine). Talk with your provider or pharmacist if you have any questions about interactions with this medication.

                          faqs

                          Frequently asked questions about Osmolex ER (amantadine)

                          How does Osmolex ER (amantadine) work?
                          Amantadine is thought to work by raising the levels of dopamine in the brain. This helps ease some movement-related symptoms of PD, such as slowed movement, tremor, and trouble balancing. In particular, Osmolex ER (amantadine) is a long-acting version of amantadine that's taken once a day in the morning.
                          Does Osmolex ER (amantadine) help essential tremors?
                          Osmolex ER (amantadine) isn't FDA-approved to help with essential tremors. Essential tremors are different from tremors in PD. Essential tremors often worsen when you're doing purposeful movements, such as writing. Tremors from PD often happen at rest and get better with purposeful movements. According to American Academy of Neurology guidelines, Osmolex ER (amantadine) hasn't been shown to help with essential tremors and isn't recommended in its treatment.
                          Can Osmolex ER (amantadine) be crushed?
                          It's not recommended to crush or chew the Osmolex ER (amantadine) tablets since this can change how the medication gets absorbed in your body. Make sure to swallow all tablets whole. If you've trouble swallowing pills, talk with your provider about other options.
                          Can Osmolex ER (amantadine) be stopped suddenly?
                          If you want to stop Osmolex ER (amantadine), talk with your provider. Don't stop taking Osmolex ER (amantadine) suddenly. Doing so can raise your risk for life-threatening withdrawal symptoms similar to neuroleptic malignant syndrome (NMS) such as fever, muscle rigidity, and confusion. Stopping treatment suddenly can also worsen PD symptoms. If you want to stop Osmolex ER (amantadine), your provider can help you do so safely by lowering your dose slowly over time.
                          Does Osmolex ER (amantadine) cause constipation?
                          Osmolex ER (amantadine) can commonly cause constipation as a side effect. To prevent this side effect, consider taking 20 mg to 35 mg per day of fiber. Also, drink fluids or water regularly to stay hydrated while you're taking Osmolex ER (amantadine). If you experience constipation, ask your provider or a pharmacist about appropriate medications you can take for relief.
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                          What are the risks and warnings for Osmolex ER (amantadine)?

                          Osmolex ER (amantadine) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.

                          risk-warning

                          Falling asleep during daily activities

                          • Risk factors: History of sleep problems | Taking sedatives or medications that make you drowsy

                            Osmolex ER (amantadine) can cause you to fall asleep during the day, even if you don't feel sleepy. This can sometimes lead to accidents if you're driving a car or operating machinery. Before starting treatment, talk to your provider if you've history of sleep disorder or if you take medications that make you drowsy. Avoid drinking alcohol while taking Osmolex ER (amantadine) because it can worsen sleepiness. Don't do activities that require your full attention, like driving, until you know how this medication affects you. If you experience falling asleep while doing normal activities, let your provider know right away.

                            risk-warning

                            Suicidal thoughts or behavior

                            • Risk factor: History of depression

                              Osmolex ER (amantadine) can raise the risk of suicidal thoughts or behavior. Watch for worsening depression or any unusual changes in mood or behavior, especially during the beginning of treatment or when the dose changes. Be aware of changes in behavior that could lead to suicidal thoughts or depression, and report anything concerning to your provider right away.

                              risk-warning

                              Problems with mood and hallucinations

                              • Risk factor: History of psychosis | Taking or suddenly stopping Osmolex ER (amantadine)

                                Osmolex ER (amantadine) can sometimes cause you to see or hear things that aren't real. This is because it can raise your dopamine levels, which can cause changes in mood, hallucinations, confusion, agitation, and aggressive behavior. The risk is higher if you've a history of mental health conditions or if you suddenly stop taking this medication. Let your provider know if you have certain mental health conditions before starting Osmolex ER (amantadine).

                                risk-warning

                                Low blood pressure and dizziness

                                • Risk factors: Drinking alcohol | Taking higher dose of Osmolex ER (amantadine)

                                  Osmolex ER (amantadine) can lower your blood pressure, which can put you at risk of fainting. Some medical conditions and medications can raise your risk for these side effects. Tell your providers about your medical history and all your medications so they can decide whether Osmolex ER (amantadine) is safe for you to take.

                                  While you're taking Osmolex ER (amantadine), it's important that you watch out for symptoms of dizziness, lightheadedness, and feeling faint when you change positions too quickly. Tell your provider right away if you have these symptoms so your provider can adjust your dose as needed. Get up slowly from a sitting or lying down position to prevent a sudden drop in blood pressure.

                                  risk-warning

                                  High fever and confusion (from withdrawal)

                                  Although rare, suddenly stopping Osmolex ER (amantadine) or lowering your dose can cause side effects similar to those of neuroleptic malignant syndrome (NMS). This is a life-threatening condition that's caused by certain mental health medications. It can cause very high fevers, confusion, irregular pulse, sweating, muscle stiffness, and changes in blood pressure. In addition, suddenly stopping Osmolex ER (amantadine) can also worsen your symptoms of Parkinson’s disease, which can lead to delirium, agitation, delusions, hallucinations. Don't stop taking Osmolex ER (amantadine) or lower your dose without talking to your provider, so they can instruct you on how to stop the medication safely.

                                  risk-warning

                                  Unusual urges and impulsive behaviors

                                  Osmolex ER (amantadine) can cause changes in people's behavior, including strong sexual or gambling urges, urges to spend money, and binge eating. This medication can also make it harder to control these urges. If these urges start to have a negative impact on your life, let your provider know. Typically stopping this medication or taking it at a lower dose can help these urges to go away. You might not know you have these urges while taking Osmolex ER (amantadine), so your provider might ask you if you've recently had these behaviors at your next visit.

                                  dosage

                                  Osmolex ER (amantadine) dosage forms

                                  The average cost for 30 tablets of 129mg of Osmolex ER (amantadine) is $498.57 with a free GoodRx coupon. This is 21.45% off the average retail price of $634.71.
                                  kit
                                  Kit
                                  DosageQuantityPrice as low asPrice per unit
                                  2 bottles of 129mg/193mg1 kit$454.20$454.20
                                  tablet
                                  Tablet
                                  DosageQuantityPrice as low asPrice per unit
                                  129mg30 tablets$498.57$16.62
                                  193mg30 tablets$498.57$16.62
                                  258mg30 tablets$454.20$15.14

                                  Typical dosing for Osmolex ER (amantadine)

                                  Most people start with 129 mg by mouth once a day in the morning. Your provider will raise your dose every week if you need better control of your symptoms. The maximum total dose is 322 mg daily.

                                  Your dose might differ if you have kidney problems.

                                  interactions

                                  Interactions between Osmolex ER (amantadine) and other drugs

                                  Osmolex ER (amantadine) may interact with certain medications or supplements. Always let your doctor and pharmacist know about any other medications or supplements (including prescribed and over-the-counter medications, vitamins, and dietary or herbal supplements) that you are currently taking. The list below does not include all possible drug interactions with Osmolex ER (amantadine). Please note that only the generic name of each medication is listed below.

                                  Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

                                  Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

                                  Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

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                                  How much does Osmolex ER (amantadine) cost?

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                                  Osmolex ER (brand)
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                                  contraindications-icon

                                  Osmolex ER (amantadine) contraindications

                                  Contraindications are specific health conditions or situations in which a person should not take a medication due to safety concerns. If you have any of the following conditions or if any of the following apply to you, let your healthcare provider know because Osmolex ER (amantadine) will not be safe for you to take.

                                  • End-stage kidney disease

                                  alternatives

                                  What are alternatives to Osmolex ER (amantadine)?

                                  There are a number of medications that your doctor can prescribe in place of Osmolex ER (amantadine). Compare a few possible alternatives below.
                                  Osmolex ER (amantadine)
                                  Used for:
                                  $454.20 Lowest GoodRx priceView Prices
                                  Trihexyphenidyl
                                  Used for:
                                  $4.00 Lowest GoodRx priceView Prices
                                  Rytary (carbidopa / levodopa)
                                  Used for:
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                                  References

                                  Best studies we found

                                  Adamas Pharma, LLC. (2021). Osmolex ER- amantadine tablet, extended release [package insert]. DailyMed.

                                  Blanpied, T.A., et al. (2005). Amantadine inhibits NMDA receptors by accelerating channel closure during channel block. The Journal of Neuroscience.

                                  Chang, C., et al. (2023). Amantadine. StatPearls.

                                  View All References (4)

                                  deVries, T., et al. (2019). Effects of renal impairment on the pharmacokinetics of once-daily amantadine extended-release tablets. CNS Drugs.

                                  D’Souza, R.S., et al. (2023). Extrapyramidal symptoms. StatPearls.

                                  Gironell, A., et al. (2006). Effect of amantadine in essential tremor: A randomized, placebo-controlled trial. Movement Disorders.

                                  Zesiewicz, T.A., et al. (2021). Evidence-based guideline update: Treatment of essential tremor: Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology.

                                  GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.
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