Memantine Crescent (Memantine Hydrochloride)

Memantine is used in the management of neurodegenerative conditions that involve glutamatergic excitotoxicity, primarily Alzheimer's disease.

• Alzheimer's disease (moderate to severe): improves cognition, daily functioning, and global clinical status.
• Behavioral disturbances associated with Alzheimer's disease: may reduce agitation and aggression.
• Vascular dementia (off‑label in some regions): used to support cognitive function when combined with other therapies.

• Memantine acts as a non‑competitive antagonist at the NMDA (N‑methyl‑D‑aspartate) receptor ion channel. By binding within the channel at moderate affinity and low voltage dependence, it blocks excessive calcium influx caused by pathological glutamate activation, thereby reducing excitotoxic neuronal injury while preserving normal synaptic transmission.

Memantine is generally well tolerated, but several adverse reactions have been reported.

Common Side Effects

• Dizziness: mild to moderate vertigo or light‑headedness.
• Headache: transient cranial pain.
• Constipation: reduced bowel motility.
• Confusion: temporary mental clouding.
• Fatigue: feeling unusually tired.
• Hypertension: modest increase in blood pressure.

Serious or Rare Side Effects

• Seizures: rare occurrence of convulsive episodes.
• Allergic reactions: rash, pruritus, or angioedema.
• Hallucinations: visual or auditory disturbances.
• Cardiac arrhythmias: irregular heart rhythm.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Hepatic dysfunction: elevated liver enzymes.

Memantine should be used with caution in specific clinical situations.

• Renal impairment: dose adjustment may be required; monitor renal function.
• Hepatic impairment: assess liver function before initiating therapy.
• History of seizures: monitor for increased seizure activity.
• Concomitant NMDA agonists: avoid combined use due to antagonistic effects.
• Pregnancy and breastfeeding: risk unknown; use only if benefit outweighs potential harm.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, and protect from moisture.

Memantine may interact with other medications that affect the NMDA pathway or renal excretion.

Major Interactions (Avoid)

• Amantadine: additive NMDA antagonism may increase neuropsychiatric side effects.
• Ketamine: combined NMDA blockade can intensify central nervous system effects.
• Other NMDA antagonists (e.g., dextromethorphan): risk of excessive inhibition.

Moderate Interactions (Monitor Closely)

• Acetylcholinesterase inhibitors (e.g., donepezil): monitor for synergistic cognitive effects.
• Cimetidine or other renal tubular secretion inhibitors: may raise memantine plasma levels.
• Diuretics (e.g., furosemide): assess renal function and electrolyte balance.
• Antipsychotics (e.g., haloperidol): observe for increased sedation or confusion.