Antiemetics

definition

Antiemetics are a group of drugs that are designed to suppress or prevent vomiting, nausea and nausea. The antiemetics comprise several groups of active substances that attach to different receptors.

Read more about this under Anti-Nausea Medication.

introduction

Nausea is a complex process that is supposed to protect the body by vomiting potentially toxic substances and preventing them from entering the organism. In addition, vomiting can occur in the course of cancer treatment and chemotherapy (Cytotoxic-induced vomiting), after operations (post-operative), during pregnancy and kinetosis (Motion sickness) occur and are treated with antiemetics.

Please also read our article on this Nausea

Structures involved

Several regions in the body are involved in the urge to vomit. One of them is the area postrema. This is a region of the brain in the brainstem that, with other nuclei, the Vomiting center form. It has the chemoreceptive trigger zone (CTZ). This refers to a group of neurons that has receptors that are in front of the Blood-brain barrier lie. Normally the brain is surrounded by a layer of very dense groups of cells (Blood-brain barrier), which prevents Toxins get into the brain. So that brain Nevertheless, information is provided about toxic substances that have entered the bloodstream, there is the circumventricular organs (a group of specialized brain areas that are in contact with the blood circulation has, i.e. not through the blood-brain barrier). These include the area postrema as part of the vomiting center.

Of the Gastrointestinal tract possesses (afferent) nerves that pull the brain, which the vomiting center via the nucleus tractus solitarii (NTS, a region of the brain that is closely involved in the gagging and vomiting reflex) in the presence of toxins.

The Balance organ and the Inner ear activate the vomiting center in case of kinetosis (travel sickness, Motion sickness).

Active ingredients and mode of action

So-called D2 receptor antagonists act centrally (In the brain) by Inhibition of dopamine receptors the area postrema and peripheral Activation of the upper digestive tract.
They can be divided into the Antiemetics that cross the blood-brain barrier (Perphenazine, Alizaprid, Droperidol) and the mainly peripheral, outside the central nervous system acting (Metoclopramide and domperidone). Metoclopramide (MCP) also acts as a 5-HT3 receptor antagonist and increases stomach and small intestinal motility (increased number of movements of the muscles).

You can with kinetosis, postoperative vomiting and cytostatic-induced vomiting (vomiting that by chemotherapy triggered).

H1 receptor antagonists block the histamine type 1 receptors. They are also used in the treatment of Allergies and used as a hypnotic (drug that promotes sleep and calming). Promethazine and diphenhydramine, among others, are used as antiemetics; these are among the first generation of histamine antagonists (these reach the vomiting center via the blood-brain barrier). You can at Vomiting and Kinetoses be used.

Block 5-HT3 receptor antagonists Serotonin receptors. The 5-HT3 mainly occur in the crushing center. Among other things are used Ondansetron, Granisetron, Tropisetron in post-operative vomiting and vomiting induced by cytotoxic drugs.

NK1 receptor antagonists inhibit the neurokinin receptor 1 in the vomiting center. The only active ingredient currently used is Aprepitant. It is usually used in combination with 5-HT3 antagonists and dexamethasone. Apreptinate must not be used during pregnancy and breastfeeding.

The main effect of Glucocorticoids (e.g. Dexamethasone) does not lie in the antiemetic effect, although they can be used for it. The antiemetic mode of action of glucocorticoids has not been conclusively clarified.