2.1 Dosage Information

The recommended initial dosage of OSMOLEX ER is 129 mg administered orally once daily in the morning. The dosage may be increased in weekly intervals to a maximum daily dose of 322 mg (administered as a 129 mg and 193 mg tablet), taken in the morning. 

OSMOLEX ER is not interchangeable with other amantadine immediate- or extended-release products.

For patients unable to tolerate more than 100 mg per day of immediate-release amantadine, there is no equivalent dose or dosing regimen of OSMOLEX ER.

2.2 Administration Information

OSMOLEX ER should be swallowed whole. Do not chew, crush, or divide tablets.  OSMOLEX ER can be administered without regard to food. 

2.3 Dosing in Patients with Renal Impairment

There are no modifications for the recommended initial and maximum dosage in patients with renal impairment; however, modifications are recommended for the titration interval and frequency of dosing in patients with moderate and severe renal impairment (see Table 1). 

Table 1: Recommended Titration and Frequency of OSMOLEX ER Dosing in Patients with Renal Impairment

* estimated by Modification of Diet in Renal Disease (MDRD) method

Monitor patients with renal impairment for change in renal function, especially in those with severe renal impairment receiving the maximum daily dosage of 322 mg [see Use in Specific Populations ( 8.6)].

2.4 Discontinuation, Dose Reduction, and Missed Dose

OSMOLEX ER should not be discontinued abruptly . The dose should be reduced gradually from higher doses to 129 mg daily for 1 to 2 weeks before discontinuing [see Warnings and Precautions ( 5.5)].

If a dose of OSMOLEX ER is missed, the next dose should be taken as scheduled.

5.1 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 for 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 (e.g., 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. There is insufficient information to establish that dose reduction will eliminate episodes of falling asleep while engaged in activities of daily living or daytime somnolence.

5.2 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. Amantadine can exacerbate psychiatric symptoms in patients with a history of psychiatric disorders or substance abuse.

Monitor patients for depression, including suicidal ideation or behavior. Prescribers should consider whether the benefits outweigh the risks of treatment with OSMOLEX ER in patients with a history of suicidality or depression.

5.3 Hallucination/Psychotic Behavior

Patients with a major psychotic disorder should ordinarily not be treated with OSMOLEX ER because of the risk of exacerbating psychosis.  Treatment with amantadine or abrupt withdrawal can cause confusion, psychosis, personality changes, agitation, aggressive behavior, hallucinations, paranoia, other psychotic or paranoia reactions [see Warnings and Precautions ( 5.5)] .

Monitor patients for hallucinations throughout treatment but especially after initiation and after the dose of OSMOLEX ER is increased or decreased.

5.4 Dizziness and Orthostatic Hypotension

Dizziness and orthostatic hypotension can occur with OSMOLEX ER.  Patients should be monitored for these adverse reactions, especially after starting OSMOLEX ER or increasing the dose. Concomitant use of alcohol when using OSMOLEX ER is not recommended [see Drug Interactions ( 7.4)].

5.5 Withdrawal-Emergent Hyperpyrexia and Confusion

A symptom complex resembling neuroleptic malignant syndrome (characterized by elevated temperature, muscular rigidity, altered consciousness, and autonomic instability), with no other obvious etiology, has been reported in association with rapid dose reduction, withdrawal of, or changes in drugs that increase central dopaminergic tone.

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 to avoid sudden discontinuation of OSMOLEX ER [see Dosage and Administration ( 2.4)].

5.6 Impulse Control/Compulsive Behaviors

Patients can experience intense urges to gamble, increased sexual urges, intense urges to spend money, binge eating, 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. In some cases, these urges were reported to have stopped when the dose was reduced or the medication was stopped. Because patients may not recognize these behaviors as abnormal, it is important for prescribers to specifically ask patients or their caregivers about the development of new or increased gambling urges, sexual urges, uncontrolled spending, or other urges while being treated with OSMOLEX ER. Consider dose reduction or stopping the medication if a patient develops such urges while taking OSMOLEX ER.

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Immediate-Release Amantadine

The adverse reactions listed in Table 2 were identified in clinical studies of immediate-release amantadine.  The most common adverse reactions reported in ≥5% of patients at the recommended dosage of immediate-release amantadine were nausea, dizziness/lightheadedness, and insomnia.

Table 2: Incidence of Adverse Reactions from Pooled Studies of Immediate-Release Amantadine

7.1 Other Anticholinergic Drugs

Products with anticholinergic properties may potentiate the anticholinergic-like side effects of amantadine. The dose of anticholinergic drugs or of OSMOLEX ER should be reduced if atropine-like effects appear when these drugs are used concurrently [see Warnings and Precautions ( 5.4)] . 

7.2 Drugs Affecting Urinary pH

The pH of the urine has been reported to influence the excretion rate of amantadine. Urine pH is altered by diet, drugs (e.g., carbonic anhydrase inhibitors, sodium bicarbonate), and clinical state of the patient (e.g., renal tubular acidosis or severe infections of the urinary tract).

Since the excretion rate of amantadine increases rapidly when the urine is acidic, the administration of urine acidifying drugs may increase the elimination of the drug from the body. Alterations of 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.

7.3 Live Attenuated Influenza Vaccines

Because of its antiviral properties, 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.

7.4 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 [see Warnings and Precautions ( 5.1, 5.4].

8.1 Pregnancy

Risk Summary

There are no adequate data on the developmental risk associated with use of amantadine in pregnant women. Animal studies suggest a potential risk for fetal harm with amantadine. In mice and rats, adverse developmental effects (embryolethality, increased incidence of malformations, and reduced fetal body weight) were observed when amantadine was administered to pregnant animals at clinically relevant doses [see Data].

In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The background risk for major birth defects and miscarriage for the indicated populations is unknown.

Data

Animal Data

The effects of amantadine on development have not been tested in studies conducted in animals using currently recommended methodology; however, developmental toxicity studies of amantadine have been reported in the published literature.

In mice, oral administration of amantadine (0, 10, or 40 mg/kg/day) to pregnant animals during organogenesis (gestation days 7-12) resulted in embryolethality and reduced fetal body weight at the highest dose tested, which was associated with maternal toxicity.  The no-effect dose for developmental toxicity in mice (10 mg/kg/day) is less than the maximum recommended human dose (MRHD) of 322 mg/day, based on body surface area (mg/m 2).

In rats, oral administration of amantadine (0, 40 or 120 mg/kg/day) to pregnant animals during organogenesis (gestation days 7-12) resulted in embryolethality and reduced fetal body weight at the highest dose.  The no-effect dose for developmental toxicity in this study (40 mg/kg/day) is similar to the MRHD on a mg/m 2 basis.

In another study in pregnant rats, oral administration of amantadine during organogenesis (gestation days 7-14) resulted in an increase in visceral and skeletal malformations at oral doses of 50 and 100 mg/kg/day.  The no-effect dose for teratogenicity in this study (37 mg/kg/day) is similar to the MRHD on a mg/m 2 basis.

Evaluation of parturition, lactation, and post-natal development in a limited number of litters from the mouse and rat studies described above revealed reductions in live litter size and pup weights at birth at 40 mg/kg/day in mice and 120 mg/kg/day in rats.

8.2 Lactation

Risk Summary

Amantadine is excreted in human milk, but amounts have not been quantified. There is no information on the risk to a breastfed infant, and there is insufficient information on the effect of amantadine on milk production in nursing mothers.

The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for OSMOLEX ER and any potential adverse effects on the breastfed infant from OSMOLEX ER or from the underlying maternal condition. 

8.4 Pediatric Use

Safety and effectiveness of OSMOLEX ER in pediatric patients have not been established. 

8.5 Geriatric Use

No dose adjustment is recommended on the basis of age. OSMOLEX ER is known to be substantially excreted by the kidney, and the risk of adverse reactions may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function [see Dosage and Administration ( 2.3)].

8.6 Renal Impairment

Because amantadine is mainly excreted in the urine, it accumulates in the plasma and in the body when renal function declines [see Clinical Pharmacology ( 12.3)] .

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

For patients with moderate or severe renal impairment, a reduction in dosing frequency is required. Closely monitor these patients (creatinine clearance 15 to less than 60 mL/min/1.73 m 2) if prescribed the maximum daily dosage of 322 mg [see Dosage and Administration ( 2.3].

Also, closely monitor patients with any degree of renal impairment for adverse reactions and potential changes in renal function, which may necessitate further dosage reduction.

12.1 Mechanism of Action

The mechanism by which amantadine exerts efficacy in the treatment of Parkinson’s disease and drug-induced extrapyramidal reactions is unknown. Amantadine is a weak uncompetitive antagonist of the NMDA receptor; however, it exhibits anticholinergic-like side effects such as dry mouth, urinary retention, and constipation in humans. Amantadine may have direct and indirect effects on dopamine neurons; it exerts dopaminergic-like side effects such as hallucinations and dizziness in humans. 

12.2 Pharmacodynamics

The effect of amantadine on QT prolongation was not studied in a dedicated thorough QT study.

Alcohol consumption may increase the potential for CNS effects, such as somnolence, dizziness, confusion, lightheadedness, and orthostatic hypotension [see Drug Interactions ( 7.4)] .

12.3 Pharmacokinetics

OSMOLEX ER tablet consists of an immediate-release outer layer and an extended-release core. The pharmacokinetics of amantadine from OSMOLEX ER is dose proportional across the dose range of 129 mg to 322 mg.

Absorption

Following oral administration of OSMOLEX ER, peak concentration of amantadine was observed in a median time of 7.5 hours (range 5.5 to 12 hours). After a single oral administration of the 129 mg dose, the mean (CV%) Cmax and AUC were 328 ng/ml (18%) and 8263 ng .h/ml (18%) respectively. Cmax and AUC with other dose levels of OSMOLEX ER increase proportionally. 

Effect of Food

Food does not affect the rate or the extent of absorption of OSMOLEX ER.

Distribution

Amantadine is 67% bound to plasma proteins over a concentration range of 0.1 to 2.0 μg/mL. The volume of distribution after intravenous administration is 3-8 L/kg, suggesting potential extravascular distribution.

Elimination

Amantadine is mainly eliminated renally, and approximately 85% of the administered dose is excreted unchanged in urine. After oral administration of a single 129 mg OSMOLEX ER tablet, the apparent oral clearance was approximately11 L/h. The half-life was approximately 16 hours.

 Metabolism

Metabolism accounts for only 5-15% of the total clearance for amantadine. Eight metabolites of amantadine have been identified in human urine. One metabolite, an N-acetylated compound, was quantified in human urine and accounted for 0-15% of the administered dose in multiple studies. The contribution of this metabolite to efficacy or toxicity is not known.

Excretion

Amantadine is primarily excreted by glomerular filtration and tubular secretion. The pH of the urine has been reported to influence the excretion rate of amantadine [see Drug Interactions ( 7.2)].

Specific Populations

Geriatric Patients

Amantadine is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function [see Use in Specific Populations ( 8.5)] .

Patients with Renal Impairment

The renal clearance of amantadine is significantly lower in patients with moderate or severe renal impairment, compared to healthy subjects with normal renal function. Therefore, a reduction in dosing frequency is required for patients with moderate or severe renal impairment [see Dosage and Administration ( 2.3)] . OSMOLEX ER is contraindicated in patients with end-stage renal disease (i.e., creatinine clearance below 15 mL/min/1.73 m 2) [see Contraindications ( 4)].

Male and Female Patients

In a study of young healthy subjects (n=20), mean renal clearance of amantadine, normalized for body mass index, was 1.5 fold higher in males compared to females. No dose adjustment by gender is warranted.

Drug Interaction Studies

Coadministration of quinine or quinidine with amantadine was shown to reduce the renal clearance of amantadine by about 30%.  The clinical significance of this effect is unknown.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

Animal studies designed to evaluate the carcinogenic potential of amantadine have not been conducted.

Mutagenesis

Amantadine was negative for genotoxicity in in vitro (Ames and mammalian cell [Chinese Hamster ovary and human peripheral blood lymphocytes]) assays in the presence or absence of metabolic activation and in an in vivo mouse bone marrow micronucleus assay.

Impairment of Fertility

The effects of amantadine on fertility have not been adequately tested in a study in animals conducted according to current standards.  In a reproduction study reported in the literature, oral administration of amantadine to male and female rats at a dose of 32 mg/kg/day resulted in impaired fertility.  The no-effect dose for adverse effects on fertility (10 mg/kg/day) is less than the maximum recommended human dose of 322 mg/day on a mg/m2 basis. 

16.1 How Supplied

OSMOLEX ER is available as extended-release tablets in the following configurations:

129 mg tablets:  

Round, biconvex, white coated tablets, imprinted on one side with a black “VP” over “075”

• Bottles of 30: NDC 68025-075-30
• Bottles of 90: NDC 68025-075-90

161 mg tablets:

Round, biconvex, orange coated tablets, imprinted on one side with a black "VP" over "021"

• Bottles of 30: NDC 68025-021-30
• Bottles of 90: NDC 68025-021-90

 193 mg tablets:

Round, biconvex, green coated tabled, imprinted on one side with a black “VP” over “076”

• Bottles of 30: NDC 68025-076-30
• Bottles of 90: NDC 68025-076-90

258 mg tablets:

Round, biconvex, blue coated tablets, imprinted on one side with a black “VP” over “077”

• Bottles of 30: NDC 68025-077-30

• Bottles of 90: NDC 68025-077-90

322 mg dosing kit:

• Dosing kit containing 2 bottles of 30 tablets each; NDC 68025-074-62 (1 bottle of 129 mg tablets and 1 bottle of 193 mg tablets)

16.2 Storage and Handling

Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C to 30°C (59°F to 86°F) [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP.