Antispasmodic drugs

Generality

As a rule, the term "antispasmodics" - or spasmolytics if you prefer - refers to all those drugs used in the treatment of spasms of smooth muscles, especially of the smooth muscles of the gastrointestinal tract.

Therefore, it can be said that antispasmodic drugs are indicated for the symptomatic treatment of all those conditions characterized by painful spasms of the gastrointestinal tract, as well as of the genitourinary tract. These spasms can be caused by various disorders and diseases, such as, for example, dysmenorrhea, irritable bowel syndrome, cholecystitis, colic and kidney stones, and cholangitis.
The active ingredients belonging to the category of antispasmodics are different. These active principles act in different sites and with different mechanisms of action, which will be briefly described below.

Antimuscarinic antispasmodics

As can be easily deduced from their name, antispasmodic drugs with antimuscarinic action exert their activity through the antagonization of muscarinic receptors for acetylcholine, present in the gastrointestinal tract.
The activation of these receptors, in fact, causes the excitation, and therefore the contraction of the gastroenteric smooth muscle cells.
This category of antispasmodics includes active ingredients such as octatropin (Valpinax®) and scopolamine (Buscopan®, Buscopan Compositum®, Erion®).
Furthermore, active ingredients such as rociverine (Rilaten®) and cymeter bromide (Alginor®) can also be included in this group. In fact, these molecules are able to exert a competitive antagonist action against the muscarinic receptors located in the gastrointestinal smooth muscle.
Typical side effects of this class of antispasmodics are: dry mouth, mydriasis, constipation and drowsiness. In some rare cases, tachycardia may also arise.

Antispasmodic phosphodiesterase inhibitors

Papaverine and substances with papaverine-like action belong to this class of antispasmodic drugs. This particular alkaloid, in fact, is able to inhibit the phosphodiesterase enzyme at the gastrointestinal level, through a mechanism of action that has not yet been fully identified. This inhibition leads to an increase in the levels of cyclic Adenosine Monophosphate (known more simply as cyclic AMP), the consequence of which is the release of the gastroenteric smooth muscle.
For the treatment of this kind of ailments, papaverine is usually found in pharmaceutical preparations in association with extracts of Belladonna (Antispasmina Colica®), a plant rich in atropine, a well-known alkaloid with antimuscarinic activity.
The main undesirable effects that may occur following the use of papaverine are: nausea, vomiting, constipation, difficulty in urination, visual disturbances and dizziness.
On the other hand, among the active principles with antispastic activity having a papaverine-like mechanism of action, we recall rociverine which, as stated, is also capable of exerting an antimuscarinic effect.

COMT inhibitor antispasmodics

COMTs - ie Catechol-O-Methyl Transferases - are particular enzymes responsible for the degradation of catecholamines such as adrenaline and noradrenaline.
These molecules are able to stimulate the adrenergic receptors present in the gastrointestinal tract, thus promoting the relaxation of smooth muscles.
Therefore, through the inhibition of the enzymes responsible for the metabolism of these catecholamines, the antispasmodics in question are capable of increasing - albeit indirectly - the adrenergic signal, thus leading to relaxation of the gastrointestinal smooth muscle.
Phloroglucin (Spasmex®) belongs to this group of antispasmodics. This active ingredient is particularly well tolerated. In fact, the side effects deriving from its use reported so far concern only the onset - moreover in rare cases - of allergic reactions that can occur on the skin.