What Makes OSMOLEX® ER (amantadine) Different?

Osmolex® ER delivers amantadine consistently throughout the day with the Osmodex drug delivery system.1,2

PK profile of Osmolex® ER relative to immediate release amantadine

Hourglass Icon The Osmodex delivery system provides a controlled, steady increase in amantadine concentrations that reach a maximum in a median time of 7.5 hours after administration.2

  • PK data do not provide evidence of clinical safety or efficacy.
  • There are no head-to-head studies in patients with PD comparing the safety and efficacy of OSMOLEX to that of amantadine IR.

These data come from a single-center, laboratory-blinded, randomized, 2-treatment, 2-period, 2-sequence, multiple oral dose crossover study was conducted in 24 healthy volunteers to compare 258-mg amantadine oral syrup (immediate release) twice daily.2

The efficacy of OSMOLEX® ER has been established based on bioavailability studies that compared OSMOLEX® ER to immediate-release amantadine.1,2

The pharmacokinetics of OSMOLEX® ER across 2 different dosage strengths were shown to be dose proportional.1,2


Multiple dosing options

Every patient is unique, so multiple dosing options allow you to tailor treatment to each individual patient’s needs.

Chart comparing the size and dosing options available for OSMOLEX® ER (amantadine) Chart comparing the size and dosing options available for OSMOLEX® ER (amantadine)

Actual tablet size relative to a penny.

The recommended initial dose of OSMOLEX® ER is 129 mg taken orally once-a-day in the morning.1

Warning icon

OSMOLEX® ER is not interchangeable
with other amantadine immediate-
or extended-release products1

Kidney icon

In patients with moderate or severe renal impairment, the dosage interval of Osmolex® ER is extended so the medication is given at the same dose but less frequently. Please see the prescribing information for specific instructions. Osmolex® ER is contraindicated in patients with end-stage renal disease.1

Food and drink icon

OSMOLEX® ER can be taken with or
without food. OSMOLEX® ER should be
swallowed whole. Do not crush, chew,
or divide the tablet1. Concomitant use of alcohol when using OSMOLEX ER is not recommended.

Quick Reference Dosing: OSMOLEX® ER Amantadine HCl Equivalence1

Tablets shown actual size.
NOTE: The USP Salt Policy (May 2013) requires the name and strength of the active ingredient in a drug product to be expressed in terms of the active moiety rather than the salt strength equivalent.3 Osmolex® ER is dosed as the weight of amantadine (base) whereas immediate-release amantadine is dosed as the weight of the amantadine hydrochloride salt.

Incidence of Adverse Reactions From Pooled Studies of Immediate-Release Amantadine1

Incidence Rate Adverse Reaction
5% to 10% Nausea, dizziness/lightheadedness, insomnia
1% to 5% Depression, anxiety and irritability, hallucinations, confusion, anorexia, dry mouth, constipation, ataxia, livedo reticularis, peripheral edema, orthostatic hypotension, headache, somnolence, nervousness, dream abnormality, agitation, dry nose, diarrhea, fatigue
0.1% to 1% Congestive heart failure, psychosis, urinary retention, dyspnea, skin rash, vomiting, weakness, slurred speech, euphoria, thinking abnormality, amnesia, hyperkinesia, hypertension, decreased libido, visual disturbance, punctate subepithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, optic nerve palsy
Less than 0.1% Convulsion, leukopenia, neutropenia, eczematoid dermatitis, oculogyric episodes, suicidal attempt, suicide, suicidal ideation


OSMOLEX® ER (amantadine) extended-release tablets is indicated for the treatment of Parkinson’s disease and for the treatment of drug-induced extrapyramidal reactions in adult patients.



OSMOLEX ER is contraindicated in patients with end-stage renal disease (i.e., creatinine clearance below 15 mL/min/1.73 m 2).


Falling Asleep During Activities of Daily Living and Somnolence: Patients treated with amantadine have reported falling asleep while engaged in activities of daily living, including the operation of motor vehicles, which sometimes has resulted in accidents.

Patients may not perceive warning signs, such as excessive drowsiness, or they may report feeling alert immediately prior to the event. Before initiating treatment with OSMOLEX ER, advise patients of the potential to develop drowsiness and specifically ask about factors that may increase the risk of somnolence with OSMOLEX ER, such as concomitant sedating medications, alcohol, or the presence of a sleep disorder. If a patient develops daytime sleepiness or episodes of falling asleep during activities that require full attention (eg, driving a motor vehicle, conversations, eating), OSMOLEX ER should ordinarily be discontinued. If a decision is made to continue OSMOLEX ER, advise patients not to drive and to avoid other potentially dangerous activities that might result in harm if they become somnolent.

Suicidality and Depression: Suicide, suicide attempts, and suicidal ideation have been reported in patients with and without prior history of psychiatric illness while treated with amantadine. Monitor patients for depression, including suicidal ideation or behavior. Prescribers should consider whether the benefits of treatment with OSMOLEX ER outweigh the risks in patients with a history of suicidality or depression.

Hallucinations/Psychotic Behavior: Patients with a major psychotic disorder should ordinarily not be treated with OSMOLEX ER due to the risk of exacerbating psychosis. Monitor patients for hallucinations throughout treatment but especially after initiation and after the dose of OSMOLEX ER is increased or decreased.

Dizziness and Orthostatic Hypotension: Patients should be monitored for these adverse reactions, especially after starting OSMOLEX ER or increasing the dose.

Withdrawal-Emergent Hyperpyrexia and Confusion: Abrupt discontinuation of OSMOLEX ER may cause an increase in the symptoms of Parkinson’s disease or cause delirium, agitation, delusions, hallucinations, paranoid reaction, stupor, anxiety, depression, or slurred speech . It is recommended that patients avoid sudden discontinuation of OSMOLEX ER.

Impulse Control/Compulsive Behaviors: Patients can experience increased sexual urges, and intense urges to gamble, spend money, binge eat, and/or other intense urges, and the inability to control these urges while taking one or more of the medications that increase central dopaminergic tone, including OSMOLEX ER. It is important for prescribers to specifically ask patients or their caregivers about the development of new or increased urges while being treated with OSMOLEX ER. Consider dose reduction or stopping the medication if a patient develops such urges while taking OSMOLEX ER.


The most common adverse reactions reported in ≥5% of patients at the recommended dosage of immediate-release amantadine were nausea, dizziness/lightheadedness, and insomnia.


Other Anticholinergic Drugs: The dose of anticholinergic drugs or of OSMOLEX ER should be reduced if atropine-like effects appear when these drugs are used concurrently.

Drugs Affecting Urinary pH: The pH of urine has been reported to influence the excretion rate of amantadine. Alterations in urine pH towards the alkaline condition may lead to an accumulation of the drug with a possible increase in adverse reactions. Monitor for efficacy or adverse reactions under conditions that alter the urine pH to more acidic or alkaline, respectively.

Live Attenuated Influenza Vaccines: Amantadine may interfere with the efficacy of live attenuated influenza vaccines. Therefore, live vaccines are not recommended during treatment with OSMOLEX ER. Inactivated influenza vaccines may be used as appropriate.

Alcohol: Concomitant use with alcohol is not recommended, as it may increase the potential for central nervous system effects such as somnolence, dizziness, confusion, lightheadedness, and orthostatic hypotension.

Please see full Prescribing Information.


  1. OSMOLEX® ER. Prescribing information. Adamas Pharmaceuticals, Inc.; 2021.
  2. DeVries T, Dentiste A, Handiwala L, Jacobs D. Bioavailability and pharmacokinetics of once-daily amantadine extended-release tablets in healthy volunteers: results from three randomized, crossover, open-label phase 1 studies. Neurol Ther. 2019. DOI: 10.1007/s40120-019-0144-1.
  3. Center for Drug Evaluation and Research. Naming of drug products containing salt drug substances: guidance for industry. US Food and Drug Administration website. https://www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation/guidances/ucm379753.pdf. Published June 2015. Accessed March 23, 2018.