Parasympathomimetics, also known as cholinomimetics, are drugs that mimic the action of acetylcholine (Ach) by directly interacting with cholinergic receptors or increasing the availability of Ach at these sites. They are classified based on their chemical structure and modifications can be made to the quaternary ammonium group, ethylene group, or acyloxy group to influence activity and stability. Parasympathomimetics work by inhibiting the enzyme acetylcholinesterase, which normally breaks down Ach, thus indirectly increasing the concentration of Ach in synapses.

1. Parasympathomimetics
Agents
Prepared By:
Aditi
Assistant Professor
School of Pharmacy
MMUS, Ambala

2. Parasympathomimetics Agents
⚫SYNONYM: Cholinomimetic , Parasympathomimetics
⚫These are the drugs which mimics the action of Ach
either by directly interacting with cholinergic
receptors or by increasing availability of Ach at these
sites.

3. CLASSIFICATION OF
Parasympathomimetics/ Cholinergic
drugs

4. SAR/CHEMISTRY OF
PARASYMPATHOMIMETICS
General Structure

5. MODIFICATION OF QUATERNARY
AMMONIUM GROUP
⚫This grp can be replaced by Phosphonium and
Selenium grp , activity will remain same but used
because of adverse effect.
⚫The N should be quaternary charged
⚫Methyl group should be present on N.

6. MODIFICATION OF
ETHYLENE GROUP
⚫Any increase or decrease in chain length decreases
the activity.
⚫Branching is allowed at beta 2c of ammonium group.
⚫E.g.. Methacholine

7. MODIFICATION OF ACYLOXY
GROUP
⚫Ester group hydrolysis is very fast so not used for oral
route and passes through 1st pass metabolism. Due to
this instability resistant group is introduced i.e.
carbamic acid ester was developed.
⚫E.g.: Carbachol

8. Mechanism of Acetylcholinesterase
Acetylcholinesterase causes the metabolism of acetylcholine into acetic
acid and choline

9. Mechanism of
Acetylcholinesterase INHIBITORS
These inhibitors interact with the enzyme
and prevent this enzyme to interact with
acetylcholine.
Thus indirectly increases concentration of
acetylcholine in synapse.
ANd this is the aim for parasympathomimetics.