Prescription Drug Information: Memantine Hydrochloride

MEMANTINE HYDROCHLORIDE- memantine hydrochloride tablet
Preferred Pharmaceuticals Inc.

1 INDICATIONS & USAGE

Memantine hydrochloride USP is indicated for the treatment of moderate to severe dementia of the Alzheimer’s type.

2 DOSAGE & ADMINISTRATION

The recommended starting dose of Memantine hydrochloride is 5 mg once daily. The dose should be increased in 5 mg increments to 10 mg/day (5 mg twice daily), 15 mg/day (5 mg and 10 mg as separate doses), and 20 mg/day (10 mg twice daily). The minimum recommended interval between dose increases is one week. The dosage shown to be effective in controlled clinical trials is 20 mg/day.
Memantine hydrochloride can be taken with or without food. If a patient misses a single dose of memantine hydrochloride, 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 for several days, dosing may need to be resumed at lower doses and retitrated as described above.
Specific Populations
Renal Impairment
A target dose of 5 mg twice daily is recommended in patients with severe renal impairment (creatinine clearance of 5 – 29 mL/min based on the Cockcroft-Gault equation).
Hepatic Impairment memantine hydrochloride should be administered with caution to patients with severe hepatic impairment [see Clinical Pharmacology (12.3)].

3 DOSAGE FORMS & STRENGTHS

Memantine hydrochloride 5 mg tablet: Peach color, capsule shape, film-coated tablet, debossed with “CL27” on one side and plain on the other side.
Memantine hydrochloride 10 mg tablet: Gray color, capsule shape, film-coated tablet, debossed with “CL28” on one side and plain on the other side.

4 CONTRAINDICATIONS

Memantine hydrochloride is contraindicated in patients with known hypersensitivity to memantine hydrochloride or to any excipients used in the formulation.

5 WARNINGS AND PRECAUTIONS

5.1 Genitourinary Conditions

Conditions that raise urine pH may decrease the urinary elimination of memantine resulting in increased plasma levels of memantine [see Drug Interactions (7.1)].

6 ADVERSE REACTIONS

6.1 Clinical Trials Experience

Memantine hydrochloride was evaluated in eight double-blind placebo-controlled trials involving a total of 1862 dementia (Alzheimer’s disease, vascular dementia) patients (940 patients treated with memantine hydrochloride and 922 patients treated with placebo) for a treatment period up to 28 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 clinical practice.
Adverse Events Leading to Discontinuation
In placebo-controlled trials in which dementia patients received doses of memantine hydrochloride up to 20 mg/day, the likelihood of discontinuation because of an adverse reaction was the same in the memantine hydrochloride group (10.1%) as in the placebo group (11.5%). No individual adverse reaction was associated with the discontinuation of treatment in 1% or more of memantine hydrochloride-treated patients and at a rate greater than placebo.
Most Common Adverse ReactionsIn double-blind placebo-controlled trials involving dementia patients, the most common adverse reactions (incidence ≥ 5% and higher than placebo) in patients treated with memantine hydrochloride were dizziness, headache, confusion and constipation. Table 1 lists all adverse reactions that occurred in at least 2% of patients treated with memantine hydrochloride and at an incidence greater than placebo.

Table 1: Adverse Reactions Reported in Controlled Clinical Trials in at Least 2% of Patients Receiving Memantine Hydrochloride and at a Higher Frequency than Placebo-treated Patients

Adverse Reaction

Placebo (N = 922) %

Memantine Hydrochloride (N = 940) %

Body as a Whole

Fatigue

1

2

Pain

1

3

Cardiovascular System

Hypertension

2

4

Central and Peripheral Nervous System

Dizziness

5

7

Headache

3

6

Gastrointestinal System

Constipation

3

5

Vomiting

2

3

Musculoskeletal System

Back pain

2

3

Psychiatric Disorders

Confusion

5

6

Somnolence

2

3

Hallucination

2

3

Respiratory System

Coughing

3

4

Dyspnea

1

2

The overall profile of adverse reactions and the incidence rates for individual adverse reactions in the subpopulation of patients with moderate to severe Alzheimer’s disease were not different from the profile and incidence rates described above for the overall dementia population.
Seizures
Memantine hydrochloride has not been systematically evaluated in patients with a seizure disorder. In clinical trials of memantine hydrochloride, seizures occurred in 0.2% of patients treated with memantine hydrochloride and 0.5% of patients treated with placebo.

6.2 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.

7 DRUG INTERACTIONS

7.1 Drugs that Make the 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.

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

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

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Risk Summary

There are no adequate data on the developmental risk associated with the use of memantine hydrochloride 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 [see Data ].

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

Data

Animal Data

Oral administration of memantine (0, 2, 6, or 18 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 3 times the maximum recommended human daily dose (MRHD) of memantine hydrochloride (20 mg) on a body surface area (mg/m2) basis.

Oral administration of memantine to rabbits (0, 3, 10, or 30 mg/kg/day) during the period of organogenesis resulted in no adverse developmental effects. The highest dose tested is approximately 30 times the MRHD of memantine hydrochloride on a mg/m2 basis.

In rats, memantine (0, 2, 6, or 18 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. The higher no-effect dose for adverse developmental effects (6 mg/kg/day) is 3 times the MRHD of memantine hydrochloride on a mg/m2 basis.

Oral administration of memantine (0, 2, 6, or 18 mg/kg/day) to rats from late gestation throughout lactation to weaning, resulted in decreased pup weights at the highest dose tested. The higher no-effect dose (6 mg/kg/day) is approximately 3 times the MRHD of memantine hydrochloride on a mg/m2 basis.

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