Direct parasympathomimetics

Parasympathomimetics are drugs that mimic the effects of the parasympathetic nervous system. Direct parasympathomimetics are substances that act directly on M receptors. They mimic the properties of acetylcholine.

Effects and uses
They increase the tone and motility of the GIT and smooth muscles. The main indication for the use of direct PSMs is GIT and bladder atony after general anesthesia.

Adverse effects

 * Diarrhea;
 * perspiration;
 * miosis ;
 * nausea ;
 * increased salivation;
 * bradycardia ;
 * reduced cardiac output.

Contraindications

 * Urinary tract obstruction;
 * megacolon

Acetylcholine
It is not absorbed from the GIT. Administration iv – for rapid breakdown by acetylcholinesterase ( ACHE ) only works for a short time.

Betanechol
Degraded by glutyrylcholinesterase - slowly metabolized. Use for bladder detrusor stimulation.

Carbachol
Degraded by glutyrylcholinesterase - slowly metabolized. It does not cross the BBB ( blood-brain barrier ). Used as a miotic in glaucoma.

Pilocarpine
An alkaloid of vegetable origin. It has a tertiary N atom, is characterized by increased lipophilicity and good penetration into the CNS and cornea. It is an agonist of muscarinic receptors. It is mainly used in ophthalmology, where it induces miosis, it is used in glaucoma and xerostomia.

Related Articles

 * Parasympathomimetics
 * Indirect parasympathomimetics
 * Sympathomimetics
 * Sympatholytics