Memantine Hydrochloride 14 mg Capsule, Extended Release, 90-count — NDC 65162-783-09 (Billing 65162-0783-09)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Persistent activation of central nervous system N-methyl-D-aspartate (NMDA) receptors by the excitatory amino acid glutamate has been hypothesized to contribute to the symptomatology of Alzheimer’s disease. Memantine is postulated to exert its therapeutic effect through its action as a low to moderate affinity uncompetitive (open-channel) NMDA receptor antagonist which binds preferentially to the NMDA receptor-operated cation channels. There is no evidence that memantine prevents or slows neurodegeneration in patients with Alzheimer’s disease.

12.2Pharmacodynamics Memantine showed low to negligible affinity for GABA, benzodiazepine, dopamine, adrenergic, histamine and glycine receptors and for voltage-dependent Ca 2+ , Na+, or K + channels. Memantine also showed antagonistic effects at the 5HT 3 receptor with a potency similar to that for the NMDA receptor and blocked nicotinic acetylcholine receptors with one-sixth to one-tenth the potency. In vitro studies have shown that memantine does not affect the reversible inhibition of acetylcholinesterase by donepezil, galantamine, or tacrine.

12.3Pharmacokinetics Memantine is well absorbed after oral administration and has linear pharmacokinetics over the therapeutic dose range. It is excreted predominantly unchanged in urine and has a terminal elimination half-life of about 60-80 hours. In a study comparing 28 mg once daily memantine hydrochloride extended-release capsules to 10 mg twice daily NAMENDA, the C max and AUC 0-24 values were 48% and 33% higher for the XR dosage regimen, respectively.

Absorption After multiple dose administration of memantine hydrochloride extended-release capsules, memantine peak concentrations occur around 9 to 12 hours post-dose. There is no difference in the absorption of memantine hydrochloride extended-release capsules when the capsule is taken intact or when the contents are sprinkled on applesauce. There is no difference in memantine exposure, based on C max or AUC, for memantine hydrochloride extended-release capsules whether that drug product is administered with food or on an empty stomach.

However, peak plasma concentrations are achieved about 18 hours after administration with food versus approximately 25 hours after administration on an empty stomach. Distribution The mean volume of distribution of memantine is 9 to 11 L/kg and the plasma protein binding is low (45%). Elimination Metabolism Memantine undergoes partial hepatic metabolism.

The hepatic microsomal CYP450 enzyme system does not play a significant role in the metabolism of memantine. Excretion Memantine is excreted predominantly unchanged in the urine and has a terminal elimination half-life of about 60 to 80 hours. About 48% of administered drug is excreted unchanged in urine; the remainder is converted primarily to three polar metabolites which possess minimal NMDA receptor antagonistic activity: the N-glucuronide conjugate, 6-hydroxy-memantine, and 1-nitroso-deaminated memantine.

A total of 74% of the administered dose is excreted as the sum of the parent drug and the N-glucuronide conjugate. Renal clearance involves active tubular secretion moderated by pH dependent tubular reabsorption. Specific Populations Elderly The pharmacokinetics of memantine in young and elderly subjects are similar.

Gender Following multiple dose administration of memantine hydrochloride 20 mg daily, females had about 45% higher exposure than males, but there was no difference in exposure when body weight was taken into account. Renal Impairment Memantine pharmacokinetics were evaluated following single oral administration of 20 mg memantine hydrochloride in 8 subjects with mild renal impairment (creatinine clearance, CLcr, > 50 to 80 mL/min), 8 subjects with moderate renal impairment (CLcr 30 to 49 mL/min), 7 subjects with severe renal impairment (CLcr 5 to 29 mL/min) and 8 healthy subjects (CLcr > 80 mL/min) matched as closely as possible by age,… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Persistent activation of central nervous system N-methyl-D-aspartate (NMDA) receptors by the excitatory amino acid glutamate has been hypothesized to contribute to the symptomatology of Alzheimer’s disease. Memantine is postulated to exert its therapeutic effect through its action as a low to moderate affinity uncompetitive (open-channel) NMDA receptor antagonist which binds preferentially to the NMDA receptor-operated cation channels. There is no evidence that memantine prevents or slows neurodegeneration in patients with Alzheimer’s disease.

12.3Pharmacokinetics Memantine is well absorbed after oral administration and has linear pharmacokinetics over the therapeutic dose range. It is excreted predominantly unchanged in urine and has a terminal elimination half-life of about 60-80 hours. In a study comparing 28 mg once daily memantine hydrochloride extended-release capsules to 10 mg twice daily NAMENDA, the C max and AUC 0-24 values were 48% and 33% higher for the XR dosage regimen, respectively.

Absorption After multiple dose administration of memantine hydrochloride extended-release capsules, memantine peak concentrations occur around 9 to 12 hours post-dose. There is no difference in the absorption of memantine hydrochloride extended-release capsules when the capsule is taken intact or when the contents are sprinkled on applesauce. There is no difference in memantine exposure, based on C max or AUC, for memantine hydrochloride extended-release capsules whether that drug product is administered with food or on an empty stomach.

However, peak plasma concentrations are achieved about 18 hours after administration with food versus approximately 25 hours after administration on an empty stomach. Distribution The mean volume of distribution of memantine is 9 to 11 L/kg and the plasma protein binding is low (45%). Elimination Metabolism Memantine undergoes partial hepatic metabolism.

The hepatic microsomal CYP450 enzyme system does not play a significant role in the metabolism of memantine. Excretion Memantine is excreted predominantly unchanged in the urine and has a terminal elimination half-life of about 60 to 80 hours. About 48% of administered drug is excreted unchanged in urine; the remainder is converted primarily to three polar metabolites which possess minimal NMDA receptor antagonistic activity: the N-glucuronide conjugate, 6-hydroxy-memantine, and 1-nitroso-deaminated memantine.

A total of 74% of the administered dose is excreted as the sum of the parent drug and the N-glucuronide conjugate. Renal clearance involves active tubular secretion moderated by pH dependent tubular reabsorption. Specific Populations Elderly The pharmacokinetics of memantine in young and elderly subjects are similar.

Gender Following multiple dose administration of memantine hydrochloride 20 mg daily, females had about 45% higher exposure than males, but there was no difference in exposure when body weight was taken into account. Renal Impairment Memantine pharmacokinetics were evaluated following single oral administration of 20 mg memantine hydrochloride in 8 subjects with mild renal impairment (creatinine clearance, CLcr, > 50 to 80 mL/min), 8 subjects with moderate renal impairment (CLcr 30 to 49 mL/min), 7 subjects with severe renal impairment (CLcr 5 to 29 mL/min) and 8 healthy subjects (CLcr > 80 mL/min) matched as closely as possible by age, weight and gender to the subjects with renal impairment.

Mean AUC 0-∞ increased by 4%, 60%, and 115% in subjects with mild, moderate, and severe renal impairment, respectively, compared to healthy subjects. The terminal elimination half-life increased by 18%, 41%, and 95% in subjects with mild, moderate, and severe renal impairment, respectively, compared to healthy subjects. Hepatic Impairment Memantine pharmacokinetics were evaluated following the administration of single oral doses of 20 mg in 8 subjects with moderate hepatic impairment (Child-Pugh Class B, score 7-9) and 8 subjects who were age-, gender-, and weight-matched to the hepatically-impaired subjects.

There was no change in memantine exposure (based on C max and AUC) in subjects with moderate hepatic impairment as compared with healthy subjects. However, terminal elimination half-life increased by about 16% in subjects with moderate hepatic impairment as compared with healthy subjects. Drug-Drug Interactions Use with Cholinesterase Inhibitors Co-administration of memantine with the AChE inhibitor donepezil did not affect the pharmacokinetics of either compound.

Furthermore,… [Excerpted — this section continues on DailyMed.]

12.2Pharmacodynamics Memantine showed low to negligible affinity for GABA, benzodiazepine, dopamine, adrenergic, histamine and glycine receptors and for voltage-dependent Ca 2+ , Na+, or K + channels. Memantine also showed antagonistic effects at the 5HT 3 receptor with a potency similar to that for the NMDA receptor and blocked nicotinic acetylcholine receptors with one-sixth to one-tenth the potency. In vitro studies have shown that memantine does not affect the reversible inhibition of acetylcholinesterase by donepezil, galantamine, or tacrine.

14 CLINICAL STUDIES The effectiveness of memantine hydrochloride extended-release capsules as a treatment for patients with moderate to severe Alzheimer’s disease was based on the results of a double-blind, placebo-controlled trial. 24-week Study of Memantine Hydrochloride Extended-release Capsules This was a randomized double-blind clinical investigation in outpatients with moderate to severe Alzheimer’s disease (diagnosed by DSM-IV criteria and NINCDS-ADRDA criteria for AD with a Mini Mental State Examination (MMSE) score ≥ 3 and ≤ 14 at Screening and Baseline) receiving acetylcholinesterase inhibitor (AChEI) therapy at a stable dose for 3 months prior to screening.

The mean age of patients participating in this trial was 76.5 years with a range of 49-97 years. Approximately 72% of patients were female and 94% were Caucasian. Study Outcome Measures The effectiveness of memantine hydrochloride extended-release capsules was evaluated in this study using the co-primary efficacy parameters of Severe Impairment Battery (SIB) and the Clinician’s Interview-Based Impression of Change (CIBIC-Plus).

The ability of memantine hydrochloride extended-release capsules to improve cognitive performance was assessed with the Severe Impairment Battery (SIB), a multi-item instrument that has been validated for the evaluation of cognitive function in patients with moderate to severe dementia. The SIB examines selected aspects of cognitive performance, including elements of attention, orientation, language, memory, visuospatial ability, construction, praxis, and social interaction. The SIB scoring range is from 0 to 100, with lower scores indicating greater cognitive impairment.

The ability of memantine hydrochloride extended-release capsules to produce an overall clinical effect was assessed using a Clinician’s Interview Based Impression of Change that required the use of caregiver information, the CIBIC-Plus. The CIBIC-Plus is not a single instrument and is not a standardized instrument like the ADCS-ADL or SIB. Clinical trials for investigational drugs have used a variety of CIBIC formats, each different in terms of depth and structure.

As such, results from a CIBIC-Plus reflect clinical experience from the trial or trials in which it was used and cannot be compared directly with the results of CIBIC-Plus evaluations from other clinical trials. The CIBIC-Plus used in this trial was a structured instrument based on a comprehensive evaluation at baseline and subsequent time-points of four domains: general (overall clinical status), functional (including activities of daily living), cognitive, and behavioral. It represents the assessment of a skilled clinician using validated scales based on his/her observation during an interview with the patient, in combination with information supplied by a caregiver familiar with the behavior of the patient over the interval rated.

The CIBIC-Plus is scored as a seven point categorical rating, ranging from a score of 1, indicating “marked improvement” to a score of 4, indicating “no change” to a score of 7, indicating “marked worsening.” The CIBIC-Plus has not been systematically compared directly to assessments not using information from caregivers (CIBIC) or other global methods. Study Results In this study, 677 patients were randomized to one of the following 2 treatments: Memantine hydrochloride extended-release capsules 28 mg/day or placebo while still receiving an AChEI (either donepezil, galantamine, or rivastigmine).

Effects on Severe Impairment Battery (SIB) Figure 1 shows the time course for the change from baseline in SIB score for the two treatment groups completing the 24 weeks of the study. At 24 weeks of treatment, the mean difference in the SIB change scores for the memantine hydrochloride extended-release capsules 28 mg/AChEI-treated (combination therapy) patients compared to the patients on placebo/AChEI (monotherapy) was 2.6 units. Using an LOCF analysis, memantine hydrochloride extended-rel… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis 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/m 2 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/m 2 basis, respectively) through 128 weeks. Mutagenesis 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. Impairment of Fertility 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/m 2 basis) orally from 14 days prior to mating through gestation and lactation in females, or for 60 days prior to mating in males.

13.2Animal Toxicology and/or Pharmacology Memantine induced neuronal lesions (vacuolation and necrosis) in the multipolar and pyramidal cells in cortical layers III and IV of the posterior cingulate and retrosplenial neocortices in rats, similar to those which are known to occur in rodents administered other NMDA receptor antagonists. Lesions were seen after a single dose of memantine. In a study in which rats were given daily oral doses of memantine for 14 days, the no-effect dose for neuronal necrosis was 4 times the maximum recommended human dose (MRHD of 28 mg/day) on a mg/m 2 basis.

In acute and repeat-dose neurotoxicity studies in female rats, oral administration of memantine and donepezil in combination resulted in increased incidence, severity, and distribution of neurodegeneration compared with memantine alone. The no-effect levels of the combination were associated with clinically relevant plasma memantine and donepezil exposures. The relevance of these findings to humans is unknown.