Drugs affecting the autonomic nervous system ( Acetylcholine / Bethanechol ) 

Acetylcholine: 

Introduction:

 Acetylcholine is one of the neurotransmitters that completes its importance in transmitting the nerve impulse from the central system to the peripheral system and then to the organ to be stimulated for certain purposes, and acetylcholine has been classified as therapeutic targets to the group of cholinergic agonists. 

Structure:

 is a quaternary ammonium compound so , it is hydrolysis by acetylcholinesterase. 

Activity: 

acetylcholine has effect on both nicotinic and muscarinic 

Pharmacological action: 

1. Acetylcholine reduces heart rate and thus reduces cardiac output. 
2. Acetylcholine reduces blood pressure.
3. Acetylcholine stimulates bowel movement and increases the secretions of the digestive system, such as the intestines. 
4. Acetylcholine works by stimulating the detrusor muscle in the bladder, which increases the contraction of this muscle and thus leads to no urine retention.
5. Acetylcholine stimulates pupil constriction in a process called miosis. 

 Acetylcholine cannot be used for therapeutic purposes due to its inhibition by cholinesterase

Bethanechol: 

Structure: 

The acetate is replaced by ester of carbamate (carbonic acid) So, it is not hydrolyzed by acetylcholinesterase. 

Activity:

 it has lack activity on nicotinic action because the choline is methylated , while it has strong activity on muscarinic . 

Pharmacological action: 

1. Bethanechol stimulates bowel movement and increases the secretions of the digestive system, such as the intestines ( as Acetylcholine ) 
2. Bethanechol  works by stimulating the detrusor muscle in the bladder, which increases the contraction of this muscle and thus leads to no urine retention ( as Acetylcholine )

Uses: 

1. atonic bladder 
2. urinary retention 
3. megacolon 

Side effect: 

1. Sweating 
2. Flushing 
3. Decrease blood pressure 
4. Diarrhea 
5. Nausea 
6. Abdominal pain 
7. Salivation 
8. Bronchospasm

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