Antispasmodics are, as their name suggests, drugs intended to treat spasms, these spasms being mainly digestive or genitourinary. Spasms are intense, brutal contractions of the so-called involuntary or smooth muscles (muscles not controlled by the will). This type of musculature allows, for example, the progression of the bolus food in our intestines. It is also found along the ureters.

There are two major classes of antispasmodics: anticholinergics and musculotropic antispasmodics.

Anticholinergic antispasmodics

They act on the nervous level by blocking acetylcholine receptors, a neurotransmitter of the parasympathetic system.

By blocking the action of acetylcholine at the level of the synapses, the passage of the nerve impulse from one neuron to the other and thus the action of the parasympathetic system is blocked.
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1 - arrival of nerve impulse 2 - release of acetylcholine into the synapse 3 - activated cholinergic receptor = influx 4 - recapture and / or destruction of acetylcholine

Smooth or involuntary musculature is dependent on the parasympathetic system and a blockage of the latter leads to relaxation of the muscles and a lifting of the spasm.

Unfortunately, these products that are highly effective also have a large number of adverse effects: ocular accommodation disorder (maintenance of dilated pupil or mydriasis), increased heart rate, dry mouth, etc. These side effects are also used in other indications. The ophthalmologist uses atropine or other anticholinergics to dilate the pupil before an examination of the fundus of the eye. In case of cardiorespiratory emergency it is also used in injection to stimulate the heart, for example.

Musculotropic antispasmodics

They have fewer side effects than cholinergic antispasmodics because they act directly on the muscles to promote their relaxation and lift the spasm. The main representatives are papaverine and phloroglucinol.

Mixed antispasmodics

This is mainly Ti-ionium. By its anticholinergic effect, it blocks the nerve transmission at the nerve endings of the parasympathetic system. By its musculotropic effect, it promotes the relaxation of the smooth muscles.