Namenda (memantine) is an approved medicine, marketed by Allergan, for the treatment of moderate to severe Alzheimer’s disease (AD).
How Namenda works
The brain uses chemical messengers, called neurotransmitters, to pass signals between nerve cells. Different neurotransmitters have different roles; for example, glutamate is involved in learning and memory. Normally, glutamate interacts with a receptor, called the NMDA receptor, found on the surface of nerve cells and which allow calcium to enter a cell. This process is essential for signaling between cells and, ultimately, in learning and memory. Precise regulation of the amount of calcium entering the cell is of considerable importance, as too much calcium can be toxic and lead to cell damage.
AD is caused by damage to nerve cells in the brain, resulting a decline in memory and the ability to think and learn. When nerve cells are damaged, it is believed that some start to release excess glutamate. The increase in glutamate causes too much calcium to enter cells, leading to further damage and a disruption in the tightly controlled memory and learning process.
Namenda works to block glutamate from accessing NMDA receptors, preventing excessive calcium from entering cells and causing damage.
Namenda in clinical trials
Two key clinical studies carried out in the U.S. demonstrated that Namenda could ease Alzheimer’s symptoms patients, and led to approval by the U.S. Food and Drug Administration (FDA) in 2003. The drug, under various brand names, is also approved for use in Europe, China and elsewhere, and is available in various forms: as immediate-release tablets, as a solution, and as an extended-release medication.
Clinical trial outcomes were assessed using three tests. The Alzheimer’s Disease Assessment Scale-Activities of Daily Living (ADAS-ADL) scores a patient on a scale of 0 to 54, and assesses the ability to perform general daily tasks such as eating, dressing, shopping, and household chores. A higher score indicates more severe symptoms, and the score usually increases each year as the disease progresses. The Clinician’s Interview-Based Impression of Change (CIBIC) is a global measure to assess the ability of a person to perform general daily tasks (eating, dressing, shopping, and household chores), as well as cognition and behavior. The Severe Impairment Battery (SIB) provides a measure of the level of cognition.
Both studies were randomized, double-blinded, and placebo controlled. Study one (MRZ 9605) showed a significant improvement by study’s end in ADAS-ADL scores in patients treated with Namenda compared to those treated with placebo, and a highly significant difference in SIB scores. Study two (MEM-MD-02) assessed the effect of Namenda in combination with Aricept (donepezil), a drug used to treat mild to moderate dementia caused by Alzheimer’s disease. The results showed that patients treated with Namenda plus Aricept showed a small but significant positive difference in both ADAS-ADL and SIB scores compared to those treated with placebo.
The most common side effects of Namenda use are reported to include fatigue, dizziness, headache, confusion, and constipation.
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