Memantine Drug Information

Memantine hydrochloride extended-release capsules are indicated for the treatment of moderate to severe dementia of the Alzheimer’s type. Memantine hydrochloride is a N-methyl-D-aspartate (NMDA) receptor antagonist indicated for the treatment of moderate to severe dementia of the Alzheimer’s type.

Recommended Dosing

The dosage of memantine hydrochloride extended-release capsules shown to be effective in a controlled clinical trial is 28 mg once daily. The recommended starting dose of memantine hydrochloride extended-release capsules is 7 mg once daily. The dose should be increased in 7 mg increments to the recommended maintenance dose of 28 mg once daily.

The minimum recommended interval between dose increases is one week. The dose should only be increased if the previous dose has been well tolerated. The maximum recommended dose is 28 mg once daily.

Memantine hydrochloride extended-release capsules can be taken with or without food. Memantine hydrochloride extended-release capsules can be taken intact or may be opened, sprinkled on applesauce, and thereby swallowed. The entire contents of each memantine hydrochloride extended-release capsules should be consumed; the dose should not be divided.

Except when opened and sprinkled on applesauce, as described above, memantine hydrochloride extended-release capsules should be swallowed whole. Memantine hydrochloride extended-release capsules should not be divided, chewed, or crushed. If a patient misses a single dose of memantine hydrochloride extended-release capsules, that patient should not double up on the next dose.

The next dose should be taken as scheduled. If a patient fails to take memantine hydrochloride extended-release capsules for several days, dosing may need to be resumed at lower doses and retitrated as described above.

Switching from Memantine Hydrochloride Tablets to Memantine Hydrochloride Extended-Release Capsules Patients treated with memantine hydrochloride tablets may be switched to memantine hydrochloride extended-release capsules as follows: It is recommended that a patient who is on a regimen of 10 mg twice daily of memantine hydrochloride tablets be switched to memantine hydrochloride extended-release capsules 28 mg once daily capsules the day following the last dose of 10 mg memantine hydrochloride tablet. There is no study addressing the comparative efficacy of these 2 regimens. In a patient with severe renal impairment, it is recommended that a patient who is on a regimen of 5 mg twice daily of memantine hydrochloride tablets be switched to memantine hydrochloride extended-release capsules 14 mg once daily capsules the day following the last dose of 5 mg memantine hydrochloride tablet.

Dosing in Patients with Renal Impairment

In patients with severe renal impairment (creatinine clearance of 5 to 29 mL/min, based on the Cockcroft-Gault equation), the recommended maintenance dose (and maximum recommended dose) is 14 mg/day.

Clinical Trials Experience

Memantine hydrochloride extended-release capsules were evaluated in a double-blind placebo-controlled trial in which a total of 676 patients with moderate to severe dementia of the Alzheimer’s type (341 patients on memantine hydrochloride extended-release capsules 28 mg/day and 335 patients on placebo) were treated for up to 24 weeks. 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. Adverse Reactions Leading to Discontinuation In the placebo-controlled clinical trial of memantine hydrochloride extended-release capsules, the proportion of patients in the memantine hydrochloride extended-release capsules group and the placebo group who discontinued treatment due to adverse reactions was 10% and 6%, respectively.

The most common adverse reaction that led to treatment discontinuation in the memantine hydrochloride extended-release capsules group was dizziness, at a rate of 1.5%. Most Common Adverse Reactions The most commonly observed adverse reactions seen in patients administered memantine hydrochloride extended-release capsules in the controlled clinical trial, defined as those occurring at a frequency of at least 5% in the memantine hydrochloride extended-release capsules group and at a frequency higher than placebo, were headache, diarrhea and dizziness. Table 1 lists adverse reactions that were observed at an incidence of ≥ 2% in the memantine hydrochloride extended-release capsules group and occurred at a rate greater than placebo.

Table 1: Adverse Reactions Observed with a Frequency of ≥ 2% in the Memantine Hydrochloride Extended-Release Capsules Group and at a Rate Greater than Placebo 1 2 Seizure Memantine has not been systematically evaluated in patients with a seizure disorder. In clinical trials of memantine, seizures occurred in 0.3% of patients treated with memantine and 0.6% of patients treated with placebo.

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of memantine. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These reactions include: Blood and Lymphatic System Disorders: agranulocytosis, leukopenia (including neutropenia), pancytopenia, thrombocytopenia, thrombotic thrombocytopenic purpura.

Cardiac Disorders: cardiac failure congestive. Gastrointestinal Disorders: pancreatitis. Hepatobiliary Disorders: hepatitis.

Psychiatric Disorders: suicidal ideation. Renal and Urinary Disorders: acute renal failure (including increased creatinine and renal insufficiency). Skin Disorders: Stevens Johnson syndrome.

Drugs That Make Urine Alkaline

The clearance of memantine was reduced by about 80% under alkaline urine conditions at pH 8. Therefore, alterations of urine pH towards the alkaline condition may lead to an accumulation of the drug with a possible increase in adverse effects. 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).

Hence, memantine should be used with caution under these conditions.

Use with Other N-methyl-D-aspartate (NMDA) Antagonists

The combined use of memantine hydrochloride extended-release capsules with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution.

Pregnancy Risk Summary There are no adequate data on the developmental risk associated with the use of memantine hydrochloride extended-release capsules in pregnant women. Adverse developmental effects (decreased body weight and skeletal ossification) were observed in the offspring of rats administered memantine during pregnancy at doses associated with minimal maternal toxicity. These doses are higher than those used in humans at the maximum recommended daily dose of memantine hydrochloride extended-release capsules.

In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown. Data Animal Data Oral administration of memantine mg/kg/day to rats during the period of organogenesis resulted in decreased skeletal ossification in fetuses at the highest dose tested.

The higher no-effect dose for adverse developmental effects (6 mg/kg) is 2 times the maximum recommended human daily dose (MRHD) of memantine hydrochloride extended-release capsules (28 mg) on a body surface area (mg/m 2 ) basis. Oral administration of memantine to rabbits mg/kg/day during the period of organogenesis resulted in no adverse developmental effects. The highest dose tested is approximately 20 times the MRHD of memantine hydrochloride extended-release capsules on a mg/m 2 basis.

In rats, memantine mg/kg/day was administered orally prior to and throughout mating and, in females, through the period of organogenesis or continuing throughout lactation to weaning. Decreased skeletal ossification in fetuses and decreased body weight in pups were observed at the highest dose tested. Oral administration of memantine mg/kg/day to rats from late gestation throughout lactation to weaning, resulted in decreased pup weights at the highest dose tested.

Pediatric Use Safety and effectiveness in pediatric patients have not been established. Memantine failed to demonstrate efficacy in two 12-week controlled clinical studies of 578 pediatric patients aged 6 to 12 years with autism spectrum disorders (ASD), including autism, Asperger’s disorder and Pervasive Development Disorder - Not Otherwise Specified (PDD-NOS). Memantine has not been studied in pediatric patients under 6 years of age or over 12 years of age.

Memantine treatment was initiated at 3 mg/day and the dose was escalated to the target dose (weight-based) by week 6. Oral doses of memantine mg extended-release capsules were administered once daily to patients with weights < kg and ≥ 60 kg, respectively. In a randomized, 12-week double-blind, placebo-controlled parallel study (Study A) in patients with autism, there was no statistically significant difference in the Social Responsiveness Scale (SRS) total raw score between patients randomized to memantine (n=54) and those randomized to placebo (n=53).

In a 12-week responder-enriched randomized withdrawal study (Study B) in 471 patients with ASD, there was no statistically significant difference in the loss of therapeutic response rates between patients randomized to remain on full-dose memantine (n=153) and those randomized to switch to placebo (n=158). The overall safety profile of memantine in pediatric patients was generally consistent with the known safety profile in adults. In Study A, the adverse reactions in the memantine group (n=56) that were reported in at least 5% of patients and at least twice the frequency of the placebo group (N=58) are listed in Table 2.

In the randomized withdrawal study (Study B), the adverse reaction in patients randomized to placebo (n=160) and reported in at least 5% of patients and twice that of the full-dose memantine treatment group (n=157) was irritability (5.0% vs 2.5%). Body weights were reduced at 45 mg/kg/day. Delays in sexual maturation were noted in male and female rats at doses ≥ 30 mg/kg/day.

Memantine induced neuronal lesions in several areas of the brain on PND 15 and 17 at doses ≥ 30 mg/kg/day. Behavioral toxicity (decrease percent of auditory startle habituation) was noted for animals in the 45 mg/kg/day dose group. The 15 mg/kg/day dose was considered the No-Observed-Adverse-Effect-Level (NOAEL) for this study.

In a second juvenile rat toxicity study, male and female juvenile rats were administered memantine mg/kg/day starting on postnatal day (PND) 7 through PND 70. Due to early memantine-related mortality, the 30 and 45 mg/kg/day dose groups were terminated without further evaluation. The NOAEL for apoptosis and neuronal degeneration was 8 mg/kg/day.

Behavioral toxicity (effects on motor activity, auditory startle habituation, and learning and memory) was noted at doses ≥ 3 mg/kg/day during treatment, but was not seen after drug discontinuation. Therefore, the 1 mg/kg/day dose was considered the NOAEL for the neurobehavioral effect in this study.

Memantine hydrochloride extended-release capsules are contraindicated in patients with known hypersensitivity to memantine hydrochloride or to any excipients used in the formulation.

Signs and symptoms most often accompanying overdosage with other formulations of memantine in clinical trials and from worldwide marketing experience, alone or in combination with other drugs and/or alcohol, include agitation, asthenia, bradycardia, confusion, coma, dizziness, ECG changes, increased blood pressure, lethargy, loss of consciousness, psychosis, restlessness, slowed movement, somnolence, stupor, unsteady gait, visual hallucinations, vertigo, vomiting, and weakness. The largest known ingestion of memantine worldwide was 2 grams in a patient who took memantine in conjunction with unspecified antidiabetic medications. This patient experienced coma, diplopia, and agitation, but subsequently recovered.

One patient participating in a memantine hydrochloride extended-release capsules clinical trial unintentionally took 112 mg of memantine hydrochloride extended-release capsules daily for 31 days and experienced an elevated serum uric acid, elevated serum alkaline phosphatase, and low platelet count. Fatal outcome has been very rarely reported with memantine, and the relationship to memantine was unclear. Because strategies for the management of overdose are continually evolving, it is advisable to contact a poison control center to determine the latest recommendations for the management of an overdose of any drug.

As in any cases of overdose, general supportive measures should be utilized, and treatment should be symptomatic. Elimination of memantine can be enhanced by acidification of urine.