Drug of the Week: Axura

So here is the Drug of the Week: Axura

Every tablet of Axura contains "MEMANTINE". This tablet is used in treatment of Alzheimers.The treatment regime of Alzheimers is complex, just like the disorder. While most of the drugs used in the tratment of Alzheimers fall in the class of Cholinester Inhibitors, which prevent the formation of Acetycholine, Memantine acts a bit differently.

Memantine is an NMDA receptor antagonist, it prevents continous stimulation of NMDA receptors by Glutamate.

But how does this dug improve conditions of Alzheimers patient is really interesting to learn!!!!

In normal conditions Glutamate activates NMDA receptors . In order to prevent excessive influx of calcium ions , Mg ion(magnesium) blocks the ion channel under resting conditions. If the NMDA receptor is activated by Glutamate, and simultaneously post synaptic neuron is depolarized Mg ion leaves the ion channel, and calcium flows in which is makes learning possible. Therefor ein Normal condition learning is based on sufficient signal over base line activity i.e enough calcium influx for sufficient signal to noise ratio.

Now in the picture it is observed that there isa good signal to noise ratio important for learning.

However in physiological conditions like Alzheimers NMDA receptors are activated by glutamate more or less continously. Under such conditions there is increased calcium influx which enhances noise and so probability of detecting signal decreases. This progresses to cognitive defects.

In this picture it is seen that the signal to noise ratio is not clear making learning difficult especially in patients suffering with Alzheimers

The reason for excessive Glutamate presence and continous activation of NMDA receptors is because excess beta amyloid prevents recycling of Glutamate i.e uptake of Glutamate by Glial cells and therefore excess glutamate masks signal transmission which results in continuated activity of NMDA receptors.

However Mg is an endogenous NMDA antagonist but has a strong voltage dependency and low affinity which results in fast blocking kinetics ,other NMDA antagonists like Dizocilpine have high affinity but are associated with slow kinetics and very weak voltage dependency.This molecule is a find beween both Mg and Dizocilpine.

Due to less voltage dependency mementine is effective than Mg , however after synaptic activations mementine like Mg can leave NMDA receptors due to voltage dependency and fast unblocking sites. It suppresses synaptic noise but allows physiological synaptic signal to be detected. This provides symptomatic neuroprotection and restoration of synaptic plasticity.

This picture shows how Mementine by blocking the NMDA receptors exerts its neuroprotection activities and when there is a physiological synapse, how it unblocks the receptors and improves cognitive activities.

The best part of this post is right here!!!

Incase you have not understood the whole text with simultaneous diagrams then the mode of action of Memantine can be seen in an animated form. Just click on the URL below and clear your doubts. http://www.memantine.com/en/mode_of_action/animation/