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Namenda XR

"March 5, 2014 -- The number of people who die from Alzheimer's disease may be five times higher than previously thought, researchers at Rush University Medical Center in Chicago say.

The study's numbers would make Alzheimer's the third lead"...

Namenda XR

Warnings
Precautions

WARNINGS

Included as part of the PRECAUTIONS section.

PRECAUTIONS

Genitourinary Conditions

Conditions that raise urine pH may decrease the urinary elimination of memantine resulting in increased plasma levels of memantine [see DRUG INTERACTIONS].

Patient Counseling Information

Advise the patient to read the FDA-approved patient labeling (Patient Information).

  • To assure safe and effective use of NAMENDA XR, the information and instructions provided in the patient information section should be discussed with patients and caregivers.
  • Instruct patients and caregivers to take NAMENDA XR only once per day, as prescribed.
  • Instruct patients and caregivers that NAMENDA XR capsules be swallowed whole. Alternatively, NAMENDA XR capsules may be opened and sprinkled on applesauce and the entire contents should be consumed. The capsules should not be divided, chewed or crushed.
  • Warn patients not to use any capsules of NAMENDA XR that are damaged or show signs of tampering.
  • If a patient misses a single dose of NAMENDA XR, that patient should not double up on the next dose. The next dose should be taken as scheduled. If a patient fails to take NAMENDA XR for several days, dosing should not be resumed without consulting that patient's healthcare professional.
  • Advise patients and caregivers that NAMENDA XR may cause headache, diarrhea, and dizziness.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment Of Fertility

There was no evidence of carcinogenicity in a 113-week oral study in mice at doses up to 40 mg/kg/day (7 times the maximum recommended human dose [MRHD] on a mg/m² basis). There was also no evidence of carcinogenicity in rats orally dosed at up to 40 mg/kg/day for 71 weeks followed by 20 mg/kg/day (14 and 7 times the MRHD on a mg/m² basis, respectively) through 128 weeks.

Memantine produced no evidence of genotoxic potential when evaluated in the in vitro S. typhimurium or E. coli reverse mutation assay, an in vitro chromosomal aberration test in human lymphocytes, an in vivo cytogenetics assay for chromosome damage in rats, and the in vivo mouse micronucleus assay. The results were equivocal in an in vitro gene mutation assay using Chinese hamster V79 cells.

No impairment of fertility or reproductive performance was seen in rats administered up to 18 mg/kg/day (6 times the MRHD on a mg/m² basis) orally from 14 days prior to mating through gestation and lactation in females, or for 60 days prior to mating in males.

Use In Specific Populations

Pregnancy

Pregnancy Category B

There are no adequate and well-controlled studies of memantine in pregnant women. NAMENDA XR should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Memantine given orally to pregnant rats and pregnant rabbits during the period of organogenesis was not teratogenic up to the highest doses tested (18 mg/kg/day in rats and 30 mg/kg/day in rabbits, which are 6 and 21 times, respectively, the maximum recommended human dose [MRHD] on a mg/m² basis).

Slight maternal toxicity, decreased pup weights and an increased incidence of non-ossified cervical vertebrae were seen at an oral dose of 18 mg/kg/day in a study in which rats were given oral memantine beginning pre-mating and continuing through the postpartum period. Slight maternal toxicity and decreased pup weights were also seen at this dose in a study in which rats were treated from day 15 of gestation through the postpartum period. The no-effect dose for these effects was 6 mg/kg, which is 2 times the MRHD on a mg/m² basis.

Nursing Mothers

It is not known whether memantine is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Namenda XR is administered to a nursing mother.

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 6-12 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 3, 6, 9, or 15 mg extended-release capsules were administered once daily to patients with weights < 20 kg, 20-39 kg, 40-59 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 [see ADVERSE REACTIONS].

In Study A, the adverse reactions in the memantine group (n=56) that were reported in at least 5% of patients and twice that in the placebo group (N=58) are listed in Table 2:

Table 2: Study A Commonly Reported Adverse Reactions With a Frequency ≥ 5% and Twice That in Placebo

Adverse Reaction Memantine
N=56
Placebo
N=58
Cough 8.9% 3.4%
Influenza 7.1% 3.4%
Rhinorrhea 5.4% 0%
Agitation 5.4% 1.7%
Discontinuations due to adverse reactionsa
Aggression 3.6% 1.7%
Irritability 1.8% 3.4%
a Reported adverse reactions leading to discontinuation in more than one patient in either treatment group.

The adverse reactions that were reported in at least 5% of patients in the 12-48 week open-label study to identify responders to enroll in Study B are listed in Table 3:

Table 3: 12-48 Week Open Label Lead-In study to Study B Commonly Reported Adverse Reactions With a Frequency ≥ 5%

Adverse Reaction Memantine N=903
Headache 8.0%
Nasopharyngitis 6.3%
Pyrexia 5.8%
Irritability 5.4%
Discontinuations due to adverse reactionsa
Irritability 1.2%
Aggression 1.0%
a At least 1% incidence of adverse reactions leading to premature discontinuation.

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%).

In a juvenile animal study, male and female juvenile rats were administered memantine (15, 30, and 45 mg/kg/day) starting on postnatal day (PND) 14 through PND 70. 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-ObservedAdverse-Effect-Level (NOAEL) for this study.

In a second juvenile rat toxicity study, male and female juvenile rats were administered memantine (1, 3, 8, 15, 30, and 45 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. Memantine induced apoptosis or neuronal degeneration in several areas of the brain on PND 8, 10, and 17 at a dose of 15 mg/kg/day. 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.

Geriatric Use

The majority of people with Alzheimer's disease are 65 years and older. In the clinical study of memantine HCl extended-release, the mean age of patients was approximately 77; over 91% of patients were 65 years and older, 67% were 75 years and older, and 14% were at or above 85 years of age. The efficacy and safety data presented in the clinical trials section were obtained from these patients. There were no clinically meaningful differences in most adverse reactions reported by patient groups ≥ 65 years old and < 65 year old.

Renal Impairment

No dosage adjustment is needed in patients with mild or moderate renal impairment. A dosage reduction is recommended in patients with severe renal impairment [see DOSAGE AND ADMINISTRATION and CLINICAL PHARMACOLOGY].

Hepatic Impairment

No dosage adjustment is needed in patients with mild or moderate hepatic impairment. Namenda XR was not studied in patients with severe hepatic impairment [see CLINICAL PHARMACOLOGY].

Last reviewed on RxList: 10/14/2014
This monograph has been modified to include the generic and brand name in many instances.

Warnings
Precautions
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