Namenda Xr (memantine HCl)
Last reviewed · Source: First Databank (FDB) drug data
Overview
Memantine hydrochloride is an N-methyl-d-aspartate (NMDA) receptor antagonist.
Memantine hydrochloride is a low- to moderate-affinity, noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist that binds preferentially to NMDA receptor-operated cation channels. The drug differs structurally and pharmacologically from other currently available agents used for the palliative treatment of Alzheimer's disease.
Memantine is thought to act by blocking the actions of glutamate, the principal excitatory neurotransmitter in the CNS. The effects of glutamate are mediated by different receptor types, including NMDA receptors, which play a role in physiologic processes such as learning and memory formation. Persistent activation of NMDA receptors by glutamate has been implicated as a possible cause of neurodegeneration in various types of dementia, including dementia of the Alzheimer's type (Alzheimer's disease), and is thought to contribute to the symptomatology of Alzheimer's disease.
In vitro studies have shown that beta-amyloid, which accumulates to form amyloid plaques in patients with Alzheimer's disease, increases the release of glutamate upon neuronal depolarization, supporting a role for pathologic NMDA receptor activation in the disease. It has been postulated that low- to moderate-affinity NMDA receptor antagonists may prevent glutamate-induced neurotoxicity without interfering with the physiologic processes mediated by the activation of NMDA receptors. However, there currently is no evidence that memantine prevents or slows neurodegeneration in patients with Alzheimer's disease.
In addition to exhibiting antagonist activity at the NMDA receptor, memantine exhibits antagonist activity at the type 3 serotonergic (5-HT3) receptor with a potency that appears to be similar to that at the NMDA receptor. Memantine also blocks the nicotinic acetylcholine receptor with a potency of about one-sixth to one-tenth that at the NMDA receptor. Memantine exhibits little or no affinity for gamma-aminobutyric acid (GABA), benzodiazepine, dopamine, adrenergic, histamine, or glycine receptors or for voltage-dependent calcium, sodium, or potassium channels.
Memantine hydrochloride is well absorbed following oral administration of conventional preparations, with peak plasma concentrations achieved in about 3-7 hours. Following multiple-dose administration of extended-release capsules of the drug, peak plasma concentrations are achieved in about 9-12 hours. Memantine is eliminated principally in urine, with approximately 48% of an administered dose excreted as unchanged drug; the remainder of the dose is converted to metabolites that exhibit minimal NMDA receptor antagonist activity.
The hepatic microsomal cytochrome P-450 (CYP) isoenzyme system does not play a substantial role in the metabolism of memantine. The terminal elimination half-life of memantine is approximately 60-80 hours.
USES: Memantine is used to treat moderate to severe confusion (dementia) related to Alzheimer's disease. It does not cure Alzheimer's disease, but it may improve memory, awareness, and the ability to perform daily functions. This medication works by blocking the action of a certain natural substance in the brain (glutamate) that is believed to be linked to symptoms of Alzheimer's disease.
Generic name: memantine HCl
Pronunciation: (MEM-an-teen)
Reference product & biosimilars
No reference, biosimilar or interchangeable associated with this drug.
Today’s intelligence on Namenda Xr
Indications
The following indications are listed for Namenda Xr:
- Moderate To Severe Alzheimer's Type Dementia
Dosing
Memantine is commercially available as memantine hydrochloride; dosage is expressed in terms of the hydrochloride salt.
Memantine hydrochloride is administered orally (as tablets, extended-release capsules, or oral solution) without regard to meals. Memantine hydrochloride tablets and oral solution are equivalent on a mg-per-mg basis.
The oral solution should be administered using the oral dosing syringe provided by the manufacturer, referring to the accompanying patient information for instructions. Memantine hydrochloride oral solution should not be mixed with any other liquid.
The extended-release capsules should be swallowed intact and not divided, chewed, or crushed; alternatively, the capsules may be opened, sprinkled on applesauce, and swallowed without chewing.
The fixed-combination preparation containing memantine hydrochloride and donepezil hydrochloride (Namzaric(R)) may be used in patients currently receiving a stable dosage of donepezil hydrochloride 10 mg daily. The fixed-combination capsules should be swallowed intact (and not divided, chewed, or crushed); alternatively, the capsules may be opened, sprinkled on applesauce, and swallowed without chewing. The entire contents of each capsule should be consumed; the dose should not be divided.
If a dose of memantine is missed, the next dose should be taken as scheduled; the dose should not be doubled to make up for a missed dose. If treatment is interrupted for several days, the drug may need to be restarted with a lower dosage and retitrated.
No dosing information is available for this tab.
No dosing information is available for this tab.
Drug interactions
There is no enhanced messaging for this drug.
There are no contraindication interactions for this drug.
There are no severe interactions for this drug.
There are no moderate interactions for this drug.
Contraindications
Known hypersensitivity to memantine hydrochloride or any ingredient in the formulation.
There are no contraindication contraindications for this drug.
There are no severe contraindications for this drug.
There are no moderate contraindications for this drug.
Adverse reactions
Common adverse effects reported with conventional preparations of memantine include dizziness, confusion, headache, and constipation.
Common adverse effects reported with the extended-release capsule formulation of the drug include headache, diarrhea, and dizziness.
There are no severe adverse reactions for this drug.
There are no less severe adverse reactions for this drug.
Precautions
No enhanced messaging available.
Safety and efficacy of memantine have not been established in pediatric patients.
Memantine has been evaluated in children 6-12 years of age with autism spectrum disorders (ASD)+; however, efficacy has not been demonstrated. (See Uses: Autism Spectrum Disorders.)
There are no adequate data to inform the developmental risks associated with the use of memantine in pregnant women. In animal reproduction studies, adverse developmental effects (e.g., decreased body weight, decreased skeletal ossification) were observed when the drug was administered to pregnant rats during the period of organogenesis or from late gestation throughout lactation to weaning at doses higher than those used clinically.
It is not known whether memantine is distributed into human milk or if the drug has any effects on the nursing infant or milk production. The known benefits of breast-feeding should be considered along with the mother's clinical need for memantine and any potential adverse effects on the breast-fed infant from the drug or underlying maternal condition.
Clinical studies have been conducted principally in older patients since dementia of the Alzheimer's type occurs mainly in patients 65 years of age or older. Memantine pharmacokinetics were similar in elderly patients and younger adults.
ICD codes
No ICD codes are available for this drug.
Formulary status
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Last reviewed · Source: First Databank (FDB) drug data
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