Namenda (memantine HCl) - Learn more about Namenda and find information for patients and caregivers including Namenda side effects, treatments, indications, FAQs and resources. Namenda (memantine HCl) is indicated for the treatment of moderate to severe Alzheimer’s disease. Namenda is available by prescription only. Namenda should not be taken by anyone who is allergic to Namenda or has had a bad reaction to Namenda or any of its components. Before starting Namenda, talk to the healthcare provider about all of the patient’s medical conditions, including kidney or liver problems. In patients with severe kidney problems, the dose of Namenda may need to be reduced. Talk to your doctor about all prescription or over-the-counter medications the patient is taking or planning to take and the recommended dosing and administration of Namenda. The most common side effects associated with Namenda treatment are dizziness, confusion, headache, and constipation. This is not a complete list of ...