**Question:** All of the following drugs are used in treatment of dementia except?

A. Memantine
B. Tacrine
C. Donepezil
D. Vincamine

**Core Concept:** Dementia is a group of symptoms that affect memory, thinking, behavior, and the ability to perform everyday tasks. Alzheimer's disease is the most common cause of dementia. Several medications are used to manage dementia symptoms, including cholinesterase inhibitors (B, C) and memantine, an NMDA receptor antagonist (A). Vincamine is a plant-derived compound with neuroprotective properties, but it is not specific to Alzheimer's disease and does not improve cognitive function, thus making it an inadequate choice for treating dementia.

**Why the Correct Answer is Right:** Memantine (D) is a selective NMDA receptor antagonist, which helps reduce the overactivation of NMDA receptors in the brain. By doing this, memantine protects neurons from damage and improves cognitive function in patients with Alzheimer's disease. It is considered a more targeted approach compared to the cholinesterase inhibitors (B, C) that work by increasing the levels of acetylcholine, a neurotransmitter involved in memory and learning.

**Why Each Wrong Option is Incorrect:**

Option B (Tacrine): Tacrine is an acetylcholinesterase inhibitor, similar to the other options (C, D). However, it has a higher risk of hepatotoxicity and is rarely used in clinical practice.

Option C (Donepezil): Similar to tacrine, donepezil is another acetylcholinesterase inhibitor that is more commonly used than tacrine due to its lower hepatotoxicity risk.

Option A (Memantine): Memantine is a selective NMDA receptor antagonist, as mentioned above, making it a more targeted approach for Alzheimer's disease treatment compared to the other options. However, it is not specific to dementia treatment and can be used for other conditions as well.

**Clinical Pearl:** Vincamine (D) is derived from Vinca rosea and is primarily used as a peripheral vasodilator to improve blood flow to the brain, which may have some neuroprotective effects. However, its effects on cognitive function in dementia are limited and inconsistent, making it an inadequate choice for treating dementia compared to the more specific and targeted treatments like memantine and donepezil.