Vomiting or emesis consists in the violent expulsion of gastric contents from the mouth; generally it is preceded by nausea, a sensation of vomiting, which, however, does not necessarily lead to actual vomiting. Often, however, nausea is followed by retching due to vomiting. contraction of the respiratory muscles, responsible for the act of vomiting.
Generally vomiting is accompanied by other symptoms, such as increased salivation, paleness, a feeling of cold and increased sweating.
Vomiting is regulated at the level of the CNS by the so-called "vomiting center", located at the bulbar level and protected by the blood-brain barrier, and by the trigger zone (CTZ), less protected and more easily accessible. This center receives peripheral stimuli from various parts of the organism: from the cerebral cortex, which can stimulate the center through tastes, smells, memories, emotions, images; from the ear, which mainly transmits information relating to the position of the body in relation to space; from different parts of the digestive system (throat, stomach, intestine); or from other organs such as the heart. Other stimuli also arrive at the heart of vomiting, such as mechanical trauma, toxic chemicals (for example toxins produced by the fetus), unpleasant or particularly important emotional events, chemotherapy. Once excited, the vomiting signal travels along afferent neurons, which send it to the salivary glands, abdominal muscles, diaphragm and various portions of the stomach, esophagus and duodenum.
Antiemetic drugs work by blocking the transmission of the signal from the vomiting center. The main antiemetics are:
- The antimuscarinics, such as scopolamine administered transdermally through patches;
- The antihistamines, anti H1 against movement sickness and pregnancy nausea (but only in exceptional cases; vice versa it is good to avoid taking them because they are able to cross the placental barrier);
- THE dopamine receptor blockers, such as the antiemetic and pyrokinetic metoclopramide (Plasil) (facilitates intestinal peristalsis and digestion);
- The antiserotonergics and i cannabinoids, used as antiemetics following chemotherapy;
- The benzodiazepines, have an "antiemetic action secondary to the main sedating action, ideal in cases of vomiting from anxiety;
- THE glucocorticoids whose antiemetic mechanism of action is unknown;
- The neurokinin-1 receptor antagonists, also these indicated in case of acute post-chemotherapy vomiting, as they inhibit the Actz receptors which, conversely, would activate the vomiting center.
- Ginger, a natural antiemetic widely used to relieve nausea in pregnancy
Other articles on "Vomiting and antiemetic drugs"
- Protective agents of the mucous membranes and prostaglandin analogues
- Constipation: Laxatives and drugs against constipation
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