An anticholinergic is an active substance that acts on the parasympathetic nervous system. The parasympathetic nervous system is part of the autonomic nervous system. It involuntarily, i.e. not subject to will, controls most of the internal organs and the blood circulation.
It has a braking and damping control function in the metabolism, thus ensuring regeneration, recuperation and protection. The transmitter (neurotransmitter) of the parasympathetic nervous system is acetylcholine. When acetylcholine is released, it acts at various receptors, which in turn transmit information from the parasympathetic nervous system to the cell.
The term ́ ́Anticholinergika ́ ́ now covers a group of active substances that suppress the effect of acetylcholine. These act on a certain type of receptor, the muscarinic receptor type. This type of receptors is found mainly in the heart and in smooth muscles, especially in the digestive tract. Here, anticholinergics cause nerve stimuli to be interrupted and thus counteract the parasympathetic nervous system which slows down and dampens the metabolism
The parasympathetic nervous system stimulates digestion and lowers the heart rate, anticholinergics have exactly the opposite effect. Anticholinergics relax the smooth muscles of the digestive tract and thus inhibit gastrointestinal activity. Furthermore, it leads to an increase in the heart rate, which is used in slow (bradycardic) heart rhythm disturbances.
Anticholinergics suppress the production of saliva, sweat and gastric juice and dilate the pupil (mydriasis) in the eye, which is used, for example, in ophthalmological examinations of the back of the eye. This dilatation of the pupil reduces the ability to see (especially in the vicinity) and leads to strong sensitivity to light (photophobia). Anticholinergics can also be used to treat urinary incontinence, very frequent urination and overactive bladder, as they have a relaxing effect on the smooth muscles.
This is also used, for example, for night-time wetting (Enuresis nocturna) in children. Anticholinergics also play a role in the treatment of Parkinson’s disease. For example, they are used in a Parkinson’s patient against body stiffness and gaze rigidity.
Atropine and similar anticholinergics
The best known active ingredient of anticholinergics is atropine. Atropine is a poisonous active ingredient found in nightshade plants such as the angel trumpet, jimsonweed and belladonna. In the Renaissance, large pupils were considered particularly beautiful among European women (́ donna ́ ́).
The use of belladonna extracts in the eyes caused the pupils to dilate for up to several days. It is still used in ophthalmology today, as it makes it easier to examine the back of the eye when the pupils are wide. However, the anticholinergic effect of atropine is also used in cases of biliary or urinary tract colic and gastrointestinal cramps.
The anticholinergic effect of atropine is also important in resuscitation after cardiovascular failure and in the treatment of heartbeats that are too slow (bradycardia) due to its rate increasing effect on the heart. Anticholinergics, which are closely related to atropine in their chemical structure, such as tiotropium bromide, are used in medicine for chronic obstructive pulmonary disease (COPD) because they dilate the bronchi. A drug related to atropine is also used to treat travel sickness. For example, a scopolamine patch suppresses the nausea. Atropine can also be used against excessive sweating (hyperhidrosis) because of its inhibitory effect on sweat production.