What is an antiemetic?
Anti-nausea medication are known as antiemetic agents or antiemetics for short. These drugs are used to prevent and treat nausea and vomiting from various causes. Adjuvant antiemetics are a group of drugs that are used with standard antiemetics to enhance its effects. Corticosteroids and benzodiazepines are adjuvant antiemetics used with other antiemetics to prevent nausea and vomiting associated with chemotherapy.
How Do Antiemetics Work?
Action of Anti-Nausea Medication
The vomit center in the brain interacts and coordinates with the complex neural networks associated with vomiting and leads to vomiting when stimulated. The vomiting center can be stimulated by a number of neural pathways involving numerous neurotransmitters like dopamine, histamine, serotonin, acetylcholine and neurokinin. Anti-nausea medication targets the receptors of these neurotransmitters.
The neural inputs to vomiting center come from chemoreceptor trigger zone (CTZ), vestibular system, vagus nerve and the central nervous system.
- The CTZ is stimulated by presence of toxic substances or certain chemicals in blood and harbors dopamine D2 receptors, serotonin 5-HT3 receptors and neurokinin NK-1 receptors.
- The vestibular system is rich in muscarinic M1 and histamine H1 receptors and is involved in conditions like motion sickness.
- The vagus nerve carries the impulses from the gastrointestinal tract to the vomiting center. The neural network of vagus is rich in muscarinic and serotonin receptors and is stimulated by disturbances in gastrointestinal system.
- The nausea and vomiting resulting from psychiatric or psychological disorders demonstrates the involvement of the central nervous system in influencing the vomiting center.
Types of Antiemetics
There are various types of antiemetics all of which act by modulating the neurotransmitter receptors mentioned above. The common types of antiemetics used are :
- 5-HT3 (serotonin) receptor antagonists
- Dopamine receptor antagonists
- Neurokinin receptor (NK-1) antagonists
- Antihistaminic drugs
- Anticholinergic drugs
- Adjuvant antiemetics
5-HT3 receptor antagonists are currently the most widely used antiemetic drugs.