Introduction, Classification and Mechanism of Action of Emetic and Antiemetic drug in Pharmacy
Emetics or Vomiting
An emetic is also known as Vomiting. It is defined as the process of evacuation or elimination of gastric content. An emetic is very helpful for the elimination of the harmful substance from stomach and duodenum.
Emetics are the drugs which cause the vomiting. It is must be important to use when poison is known to have been swallowed.
Vomiting is a physical event, it is a forceful elimination of gastric content through the mouth.
In the medulla oblongata, vomiting center or emetic center are situated, that region is known as Area postrema. In the area postrema Chemoreceptor Trigger Zone (CTZ) and Nucleus Tractus Soliterius (NTS) is also present.
Emetic Drug or Vomiting Drug
Emetic drug or vomiting drug are those drug which is responsible for the vomiting.
An emetic drug is applied when an undesirable like poison has been injected.
Vomiting drug should never be attempted if the patient is not fully conscious or if a substance is corrosive.
Some emetic drug is following…
- Apomorphine : Apomorphine is the synthetic derivative of the morphine. It acts as a dopaminergic agonist on CTZ. Apomorphin drug is injected in Intramuscular(IM) or Subcutaneous(SC) in a dose of 6mg.
Apomorphine drug are starting vomiting in 5 min. and it should not use in a respiratory depressant patient.
- Ipecacuanha : Ipecacuanha drug is a part of the dried root of Cephaelis Ipecacuanha contains emetine. It acts by irritating gastric mucosa and as well as through CTZ.
That drug is used as a syrup ipeca. The dose of Ipecacuanha in an adult is 15-30ml, in children 10-15ml and 5ml in the infant. It takes 15 min or more for the action.
Antiemetic Drug or Antivomiting Drug
Antiemetic drug or Antivomiting drug are those drugs which is responsible for the prevention of the vomiting.
Classification: They are classify as fallowing…
- Anticholinergic Drug
- H1 Antihistaminics
- Prokinetic Drug
- 5-HT3 Antagonist
- Adjuvant Antiemetics
Hyoscine and Dicyclomine are belonging to this category. It acts as the blockage of conduction nerve impulse around the cholinergic link in the pathway of leading from the vestibular apparatus to the vomiting center. Anticholinergic drugs are muscarinic receptor antagonist.
Dose- Hyoscine is used 0.2-0.4mg as oral or intramuscular. And Dicyclomine are used 10-20mg oral.
Use- Hyoscine is mostly used in motion sickness. But it also produces sedation and anticholinergic side effect. And Dicyclomine is used for motion sickness and morning sickness.
H1- Antihistaminic Drugs
H1-Antihistaminic drugs like Promethazine, Cinnarizine etc. block the H1 receptor in the area postrema part of medulla oblongata and as well as block muscarinic receptor in the CNS.
Dose- 20-25mg oral.
Use- H1 Antihistaminic drugs are mainly used in the motion sickness and small amount in morning sickness.
euroleptic drugs like Haloperidol, Chlorpromazine etc. act as an Antagonistic action on Dopamine D2 receptor in the CTZ.
Dose- 10-15mg oral.
Use- morning sickness, that drug is induced post-anesthetic nausea and vomiting, cancer chemotherapy and diseases induce vomiting for an example migraine. They are not effective in motion sickness because the vestibular probably does not involve dopaminergic link.
5-HT3 Antagonist drug like Ondansetron, Granisetron etc. are block 5-HT3 receptor in GIT, CTZ and NTS and prevent vomiting. It is use to prevent cencer chemotherapy/Radiotherapy induce vomiting. Ondansetron block emetogenic impulses both at their peripheral origin and their central relay. It does not block dopamine receptor and apomorphine or motion sickness induced vomiting.
Dose- Ondansetron use 4-8mg oral or I.V. And Granisetron use 3-7mg oral or I.V.
Use- Ondansetron use in cancer therapy, GIT infection and cytotoxic drug. And Granisetron also use in cancer therapy, GIT infection and cytotoxic But Granisetron is 10-15 time more potent than Ondansetron.
Domperidone, Metoclopramide etc. Drug are belonging to this category. Prokinetic drug are block Dopamine D2 receptor, it produces antiemetic action due to blockage of D2 receptor in CTZ.
Prokinetic drug also enhances the gastro duodenal motility and increases gastric emptying are called Prokinetic drug.
It also acts by enhancing Acetylcholine(Ach) from cholinergic neuron in the gut.
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