drugs

Antidiarrheal - Antidiarrheal drugs

Generality

Antidiarrheal drugs are medicines used to treat diarrhea.

Diarrhea is a defecation disorder characterized by the rapid and urgent emission of faeces, having a semi-liquid or watery consistency.

More than a true pathology, diarrhea generally constitutes the symptom of a basic pathological situation.

Therefore, it is clear that in the event of the appearance of this disorder it is essential to promptly identify the primary cause, so as to be able to establish an adequate therapy.

However, diarrhea is a rather debilitating disorder, which can be associated with symptoms such as abdominal cramping, pain and swelling. Furthermore, diarrhea can cause significant loss of water and mineral salts, resulting in dehydration. Therefore, in these cases, the use of anti-diarrheal drugs is essential.

Inhibitors of intestinal motility

The drugs most commonly used as antidiarrheal substances are essentially active ingredients that can inhibit intestinal motility.

The antidiarrheal inhibitors of intestinal motility are active principles of opioid origin, such as loperamide and diphenoxylate.

loperamide

Loperamide (Imodium®, Dissenten®) is an opioid drug derived from morphine and has a marked antidiarrheal activity.

Compared to morphine, loperamide is more lipophilic and struggles to overcome the blood-brain barrier; moreover, it undergoes a strong first-pass metabolism. For these reasons, at the therapeutic doses usually used, loperamide does not produce central opioid-type effects; therefore it has a low potential for abuse and dependence (so much so that the medicines that contain it are sold as drugs without a medical prescription).

Loperamide has its own antidiarrheal activity exerting an agonist effect against the opioid receptors μ and δ present in the intestine. The activation of these receptors inhibits the release of acetylcholine by cholinergic neurons, with consequent inhibition of intestinal peristalsis.

diphenoxylate

The diphenoxylate is also an opioid derivative, having properties and mechanism of action similar to those of loperamide. Therefore, also this active principle blocks the intestinal peristalsis promoted by the acetylcholine, through the agonist action against the opioid receptors present at enteric level.

However, unlike loperamide, diphenoxylate is not used on its own, but is available in pharmaceutical preparations in association with atropine sulfate. The combination with atropine - a known muscarinic antagonist - in addition to having an antispastic action at the level of smooth muscles, has the task of further increasing the blockage of intestinal peristalsis stimulated by acetylcholine.

Side effects

The side effects that may arise following the use of antidiarrheal inhibitors of intestinal peristalsis may be different depending on the active ingredient used and the sensitivity of each individual to the drug used.

However, it can be said that the main side effects that can occur consist of: constipation, flatulence, dyspeptic disorders, rashes, headaches, nausea and vomiting.

Inhibitors of intestinal secretion

Acetorfan belongs to the category of antidiarrheal inhibitors of intestinal secretion, otherwise known as racecadotril (Tiorfix®).

This active ingredient is mainly used for the treatment of acute diarrhea in children over three months of age.

Racecadotril exerts its action by inhibiting the enzyme encephalinase, that is, the enzyme responsible for the degradation of encephalins (a particular type of endogenous opioids).

In fact, the enkephalins are able to mediate, decreasing, the hypersecretion of water and electrolytes, through the link with the δ opioid receptors present in the intestine.

The main side effects that may arise following the use of racecadotril are mainly allergic reactions in sensitive individuals that manifest themselves in the form of angioedema.

Antidiarrheal microorganisms

In addition to the aforementioned antidiarrheal drugs of synthetic origin, there are also medicines very useful in the treatment of this disorder containing, in fact, antidiarrheal microorganisms.

More precisely, these medicines contain inactivated spores or microorganisms and some of these are often referred to as probiotics.

Generally, drugs containing antidiarrheal microorganisms are used for the treatment of diarrhea in young children and infants, as well as being used in adjuvant therapy for the restoration of the normal intestinal bacterial flora that can be compromised, for example, by antibiotic therapies.

In fact, these microorganisms - once assumed - are able to survive the acidic environment of the stomach, thus reaching the intestine, in which they are able to multiply and grow, favoring, precisely, the rebalancing of the bacterial flora.

Among the main antidiarrheal microorganisms currently used in therapy, we mention Bacillus clausii (Enterogermina®), Lactobacillus acidophilus (Lacteol Forte®, Yovis®) and Saccharomyces boulardii (Codex®).

Generally, this type of medicine is well tolerated and does not cause significant side effects.

However, in some cases flatulence or allergic reactions may occur.

Antidiarrheal adsorbents

As you can easily guess from their name, the adsorbent antidiarrheal - thanks to their chemical-physical peculiarities - exert their action by absorbing liquids and gases present in the intestine.

Generally, this type of antidiarrheal is well tolerated, although in some cases constipation may occur as a result of their use.

Furthermore, it is good to remember that adsorbent antidiarrheal substances can hinder the intestinal absorption of any other drugs taken orally.

Activated carbon and diosmectite (Diosmectal®) belong to this category of antidiarrheal drugs.