Problem

Solutions For An Introduction to Medicinal Chemistry Chapter 14 Problem 5Q

Step-by-Step Solution

Solution 1

Decamethonium acts as a depolarizing agent. Generally, a stimulus is applied to a muscle which causes contraction. Thus, at neuromuscular junction, acetylcholine is released which is a neurotransmitter. This chemical causes muscle contraction. On contrast, Decamethonim is a muscle relaxant which causes muscle paralysis. It is a neuromuscular blocking agent which is an agonist of nicotinic acetylcholine receptors.

Step #2 of 9

It causes depolarization thus, preventing stimulus from affecting the muscle and does not allow muscle contraction. The release of acetylcholine does not affect decamethonium activity. The membrane which is being depolarized by decamethonium remains depolarized because decamethonium is not degraded by cholinesterase. It is mainly used in anesthesia.

It causes paralysis because it continuously depolarizes the postsynaptic membrane.It lasts too long in the body.Decamethonium consists of positively charged nitrogen atoms which are linked by polymethylene chain. This separation of nitrogen atoms provides a favourable condition for the blocking action at the neuromuscular junction.

Figure: Structure of Decamethonium

Step #3 of 9

Non depolarizing agents are the agents which metabolize quickly by cholinesterase. There are also various soft drugs which metabolize quickly and lead to formation of inactive metabolites. Some of them are as follows:

1. Active diester is metabolized to toxic anhydride.