Case report: a unique presentation of memantine overdose causing echolalia and hypertension

Since 2003 when memantine was first approved for use in the management of moderate-severe Alzheimer's dementia, its use has become more widespread and is being explored in other diseases like neuropathic pain, epilepsy, and mood disorders. Our case uniquely highlights two important adverse effects in a patient who overdosed on memantine. One is hypertension, which is easy to overlook as a medication side effect. The other is echolalia which is the repetition of words and phrases spoken by another person. It is commonly seen in children with autism spectrum disorder and has been reported in older adults with head injuries, delirium, and neurocognitive disorders. The aim of this patient story is to highlight the importance of medication reconciliation with caregivers and knowledge of adverse drug reactions in patient management. This case report has been presented previously in the form of an abstract at the American Geriatrics Society Presidential poster session in May 2023.

Our patient is an 86-year-old man with mild dementia and hypertension, who was brought to the emergency department (ED) due to abrupt onset of altered mental status and auditory hallucinations. Investigations including blood work, CT head and an electroencephalogram (EEG) did not reveal an etiology for this change in his condition. Due to elevated blood pressure on presentation, a nicardipine drip was started, and he was given IV midazolam to assist with obtaining imaging. While reviewing medications with his daughter, it was noted that sixty memantine pills were missing from the bottle. Poison control was contacted and they confirmed association of these features with memantine. With supportive care, his symptoms resolved in less than 100 h, consistent with the half-life of memantine. Notably, our patient was started on Memantine one month prior to this presentation.

Hypertensive urgency and echolalia were the most striking symptoms of our patient's presentation. Though hypertension is a known sign of memantine overdose, it can easily be contributed to medication non-compliance in patients with dementia, being treated for hypertension. According to our literature review, this the first case of memantine overdose presenting with echolalia, a sign that is not commonly associated with adverse reactions to medications. This highlights the importance of an early medication review, especially with caregivers of people with dementia.