Overview
Memantine is an NMDA receptor antagonist used to treat moderate to severe Alzheimer’s disease. It helps to regulate the activity of glutamate, a chemical messenger in the brain involved in learning and memory, thereby improving cognitive function and daily functioning in patients.

Mechanism of Action
It works by acting as an uncompetitive, low-affinity antagonist at the N-methyl-D-aspartate (NMDA) receptors. In Alzheimer’s disease, overstimulation of these receptors by excessive glutamate can lead to neuronal damage. Memantine blocks this excessive stimulation while allowing normal physiological nerve impulses to continue, protecting neurons and improving cognitive function.

Dosage and Administration
The starting dose is typically 5 mg once daily, which is gradually increased over several weeks to the target maintenance dose of 10 mg twice daily (or 28 mg once daily for extended-release formulations). It can be taken with or without food.

Side Effects
Memantine is generally well-tolerated. The most common side effects include dizziness, headache, confusion, and constipation. These are usually mild to moderate and may diminish over time.

Contraindications
It is contraindicated in patients with a known hypersensitivity to memantine. Caution is required in patients with severe renal impairment, and dose adjustments may be necessary. It should also be used with caution in patients with a history of seizures or cardiovascular disease.

Pregnancy and Lactation
There are no adequate and well-controlled studies of memantine in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is not known whether it is excreted in human breast milk.