What Is Memantine Hydrochloride – Indications, Pregnancy

What Is Memantine Hydrochloride/Memantine is a primary aliphatic amine that is the 3,5-dimethyl derivative of 1-aminoadamantane. A low to moderate affinity uncompetitive (open-channel); NMDA receptor antagonist which binds preferentially to the NMDA receptor-operated cation channels. It has a role as a dopaminergic agent, an antiparkinson drug, an NMDA receptor antagonist, a neuroprotective agent, and an antidepressant. It is a member of adamantanes and a primary aliphatic amine. It is a conjugate base of memantine(1+). It derives from a hydride of adamantane.

Memantine is an amantadine derivative with low to moderate-affinity for NMDA receptors. It is a noncompetitive NMDA receptor antagonist that binds preferentially to NMDA receptor-operated cation channels. It blocks the effects of excessive levels of glutamate that may lead to neuronal dysfunction. It is under investigation for the treatment of Alzheimer’s disease, but there has been no clinical support for the prevention or slowing of disease progression.

Memantine Hydrochloride is the hydrochloride salt of memantine, a low-affinity, voltage-dependent, noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Memantine binds to and inhibits cation channels of glutamatergic NMDA receptors located in the central nervous system (CNS), preventing the prolonged influx of calcium ions and the associated neuronal excitotoxicity, and thereby potentially enhancing cognitive function. Memantine is also a 5-hydroxytryptamine type 3 (5HT3) receptor and nicotinic receptor antagonist.

Synonyms of Memantine

  • 1-Amino-3,5-dimethyladamantane
  • 1,3-Dimethyl-5-adamantanamine
  • 3,5-Dimethyl-1-adamantanamine
  • 3,5-Dimethyl-1-aminoadamantane
  • 3,5-Dimethyltricyclo(3.3.1.1(3,7))decan-1-amine
  • Memantina
  • Memantine
  • Memantinum

Mechanism of Action of Memantine

Continuous activation of the N-methyl-D-aspartate (NMDA) receptors in the central nervous system caused by glutamate are thought to cause some of the Alzheimer’s disease symptoms. This overactivation is thought to contribute to neurotoxicity due to the excitatory properties of glutamate [T556]. The pharmacological effect of memantine likely occurs via the drug’s behavior as an uncompetitive (open-channel) NMDA receptor antagonist, preventing glutamate action on this receptor. Memantine has a preference for the NMDA receptor-operated cation channels. Despite these antagonist effects, memantine has not been proven to prevent or retard the neurodegeneration seen in patients diagnosed with Alzheimer’s disease.

In addition to exhibiting antagonist activity at the NMDA receptor, memantine exhibits antagonist activity at 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.

Indication of Memantine

Antiparkinson Agents; Dopamine Agents; Excitatory Amino Acid Antagonists

  • Memantine is used to manage moderate to severe Alzheimer’s dementia. A more recent systemic review and meta-analysis indicates that memantine is beneficial as a first-line drug for the treatment of Alzheimer’s dementia. Cholinesterase inhibitors may be added to memantine for further beneficial effects on behavioral symptoms and other symptoms of dementia.
  • Treatment of patients with moderate to severe Alzheimer´s disease
  • Alzheimer’s Disease
  • Migraine
  • Autism
  • Mild Vascular dementia
  • Moderate Alzheimer’s Type Dementia
  • Moderate Vascular dementia
  • Moderate dementia of the Alzheimer’s type
  • Severe Alzheimer’s Type Dementia
  • Severe dementia of the Alzheimer’s type
  • Memantine is an oral N-methyl-D-aspartate glutamate receptor antagonist used in the therapy of Alzheimer disease and dementia
  • Memantine hydrochloride is used for the palliative treatment of moderate to severe dementia of the Alzheimer’s type (Alzheimer’s disease).
  • Treatment of cognitive deficits
  • Long-term treatment of moderate alcohol-related dementia (ARD) with memantine.
  • Medication plays an important role in the treatment of canine compulsive disorders (CCD).
  • Agents used in the treatment of Parkinson’s disease. The most commonly used drugs act on the dopaminergic system in the striatum and basal ganglia or are centrally acting muscarinic antagonists.


Contraindications of Memantine

Patients with hypersensitivity to memantine hydrochloride or any agents used in the formulation.

  • Genitourinary conditions – Conditions that raise urine pH may decrease the urinary elimination of memantine
  • Cardiovascular disease – Increased incidence of cardiac failure, angina, and hypertension occurred in clinical trials
  • Hepatic impairment – Precaution use in severe hepatic impairment; effects of the impairment on pharmacokinetics have not been established
  •  Allergies to Amantadine Analogues

Dosage of Memantine

Strengths: 2 mg/mL; 10 mg; 5 mg; 7 mg; 14 mg; 21 mg; 28 mg;

Alzheimer’s Disease

Immediate Release

  • Week 1: 5 mg orally once a day.
  • Week 2: 10 mg orally/day (Administer 5 mg twice a day.)
  • Week 3: 15 mg orally/day (Administer 5 mg and 10 mg as separate doses.)
  • Week 4/Maintenance Dose: 20 mg orally/day (Administer 10 mg twice a day.)

Extended-Release

  • Initial Dose: 7 mg orally once a day.
  • Maintenance and Maximum Dose: 28 mg orally once a day; increase the initial dose in 7 mg increments to the recommended maintenance dose.

Starting Dosage

  • 5 mg once daily

Target Dosage

  • 20 mg once daily

Titration

  • Dosage increased by 5 mg daily in weekly intervals as tolerated

Titration Schedule

  • Week 1: 5 mg daily
  • Week 2: 10 mg daily (5 mg twice daily)
  • Week 3: 15 mg daily (5 mg one time and 10 mg one time daily)
  • Week 4: 20 mg daily (10 mg twice daily)

Switching from Immediate-Release (IR) to Extended-Release (ER)

  • Start ER day after the last dosage of IR; IR 10 mg twice daily should be switched to ER 28 mg daily

Missed Dosage

  • Single-dose missed do not double up on next dose; if several dosages are missed, resume at a lower dose and titrate as tolerated

Special Population

  • Renal impairment: A target dose of 5 mg twice daily is recommended in patients with severe renal impairment (creatinine clearance of 5 to 29 mL per minutes based on the Cockroft-Gault equation)
  • Hepatic impairment: Mild to moderate no dosage adjustment necessary; severe use with caution
  • Pregnancy: FDA category B (No evidence of risk in studies; animal reproduction studies have shown adverse events); use with caution
  • Breastfeeding: It is not known if memantine is excreted in breast milk; use with caution in nursing mother
  • Pediatric use: safety and effectiveness have not been established

Dosage Forms

  • Capsule, extended-release, 24-hour, oral, as hydrochloride: Generic: 7 mg, 14 mg, 21 mg, 28 mg
  • Solution, oral, as hydrochloride: Generic: 2 mg/mL (360 mL)
  • Tablet, oral, as hydrochloride: Generic: 5 mg, 10 mg

Administration

  • Any formulation: With or without food; do not chew, crush, or divide
  • Extended-release capsules: may be swallowed whole or entire contents of capsule sprinkled on food and swallowed immediately.
  • Oral Solution: Do not mix with any other liquid; administer with provided dosing device supplied with the device consisting of a syringe, syringe adaptor cap, tubing, and other needed supplies; slowly squirt into the corner of the mouth

Side Effects of Memantine Hydrochloride

  • Bloating or swelling of the face, arms, hands, lower legs, or feet
  • behavior changes (e.g., aggression, rage, agitation, anxiety, paranoia)
  • blurred vision
  • dizziness
  • headache
  • constipation
  • dizziness
  • drowsiness
  • fatigue
  • loss of appetite
  • trouble sleeping
  • pounding in the ears
  • rapid weight gain
  • slow or fast heartbeat
  • tingling of the hands or feet
  • unusual weight gain or loss

Common

  • change in frequency of urination
  • confusion
  • change in balance and coordination especially when walking
  • fungal infection
  • hallucinations (seeing, hearing, or feeling things that are not actually there)
  • high blood pressure
  • signs of a blood clot in the arm or leg (tenderness, pain, swelling, warmth, or redness in the arm or leg)
  • signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
  • signs of heart failure (e.g., decreased heart rate, difficulty breathing, build up of fluid in the legs and ankles)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • signs of pancreatitis (e.g., abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, swollen abdomen)
  • trouble walking
  • vision changes

Rare

  • Abdominal or stomach pain
  • agitation
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • blood in the urine or stools
  • chest pain
  • coma
  • constipation
  • continuing vomiting
  • convulsions
  • dark-colored urine
  • decreased urine output
  • depression
  • fainting
  • fast, pounding, or irregular heartbeat or pulse
  • general feeling of tiredness or weakness

Drug Interactions of Memantine Hydrochloride

Memantine may interact with following drugs, supplements, & may change the efficacy of drugs

  • amantadine
  • anticholinergic medications (e.g., atropine, hyoscyamine)
  • bupropion
  • carbonic anhydrase inhibitors (e.g., acetazolamide, topiramate)
  • cimetidine
  • dextromethorphan
  • dopamine agonists (e.g., bromocriptine, pergolide, pramipexole, ropinirole)
  • hydrochlorothiazide
  • ketamine
  • levodopa
  • nicotine
  • quinidine
  • ranitidine
  • sodium bicarbonate
  • triamterene
  • trimethoprim
  • warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

Pregnancy Category of Memantine Hydrochloride

FDA Pregnancy Risk Category: B

Pregnancy

This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately. Adequate, well-controlled studies in pregnant women have not shown an increased risk of fetal abnormalities despite adverse findings in animals, or, in the absence of adequate human studies, animal studies show no fetal risk. The chance of fetal harm is remote but remains a possibility.

Breast-feeding

It is not known if memantine passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding. The safety and effectiveness of using this medication have not been established for children. Not known whether memantine is distributed into human milk. However, since many drugs are distributed into human milk, caution is advised if memantine is administered in nursing women.

Memantine has not been systematically evaluated in patients with a seizure disorder. In clinical studies, seizures occurred in 0.2% of patients receiving memantine and in 0.5% of patients receiving a placebo.


References

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