Emetics (The agents which are used to evoke vomiting) and Antiemetic (Drugs used against vomiting)

Emesis is reflux coordinated by emetic centre in medulla. The main vomiting centre is CTZ and NTS.
Toxins and drugs enter in CSF and stimulates receptors in CTZ and vomiting occurs. The receptors present in CTZ and NTS are histamine, dopamine, serotonin, cholinergic, opioids. These receptors send impulse to vomiting centre. Hence these sites should be the target for antiemetic action.
The most important receptors in emetic centre is alpha-2-adrenergic which is mainly present in cats, serotonin.
Vomiting is of three types- motion sickness, morning sickness and gastric sickness. Motion sickness mainly occurs during travelling due to the activation of CTZ due to the attack of stimulus on labyrinth to nerve VIII and then to cerebellum which then reaches to CTZ activation and then causes vomiting.
The drugs used as emetics are-
1.Apomorphine
2.Xylazine
3.3% Hydrogen Peroxide
4.Tablet salt solution
5.Activated Charcoal
Apomorphine is a semi-synthetic derivative of morphine. It stimulates the D2 receptor in CTZ. At a high dose of apomorphine vomiting, sedation and excitement is produced. But if overdose of the apomorphine occurs it leads to respiratory and cardiac depression. The respiratory and cardiac depression may be reversed by using naloxone which is a morphine derivative. Apomorphine can be injected by Intramuscular in a dose of 6mg within 5 minutes of vomiting induces. The oral dose of apomorphine is not recommended. Apomorphine has therapeutic effect in Parkinson's but not used due to side effects. Half-life of apomorphine is 40 minutes and clearance is 223 l/hrs.
Xylazine at lower dose can be used as emetic which act as alpha-2-adrenergic agonist. It has been contraindicated in hypertension, pregnancy and peptic ulcer.
3% Hydrogen Peroxide is used to produce emesis. It may cause esophagitis and gastritis.
Activated Charcoal is majorly use in case of poisoning. It is given orally to absorb the toxins or drugs to reduce their absorption is systemic circulation. Activated charcoal is not effective in case of absorbing nitrate, caustic alkali, alcohol. It may cause constipation, diarrhoea, black faeces.
Anti-emetics- The agents which are used to prevent or supress the vomiting are known as anti emetics.
The drugs used as Anti-emetics are hyoscine, dicyclomine, promethazine, diphenhydramine, dimenhydrinate, doxylamine, meclizine , cinnarizine, chlorpromazine, triflupromazine, prochlorperazine, haloperidol, metoclopramide, domperidone, cisapride, mosapride, itopride, ondansetron, granisetron, palonosetron, ramosetron, aprepitant, fosaprepitant, dexamethasone, benzodiazepines, dronabinol, nabilone.
The wide variety of drugs are available or used in prevention and the treatment of vomiting specially in cancer chemotherapy induced vomiting.
Metoclopramide is used in H1 histamine blocking activity.
Ondansetron, granisetron,dolasetron and palonosetron is used in preventing nausea and vomiting after general anaesthesia and chemotherapy.

1. Emetics and Antiemetics Guided by- Prof. Ms. Ishwari Sidwadkar . Department of Pharmacology Presented by- Ms. Ketki Mahashabde Ms. Rutuja Yadav School Of Pharmacy and Research Centre Shardanagar Baramati

2. Emetics The agents which are used to produce vomiting is known as emetics. Emetics is also known as emesis. Emesis is forceful ejection of contents of stomach in mouth. Toxic substances or poision is removed by vomiting. Two main vomiting centres are Chemoreceptor Trigger Zone (CTZ) and Nucleus Tractus Solitaries (NTS). Drugs and toxins enter into CNF and stimulates the receptor in CTZ. Following are the important receptors in CTZ: 1.Serotoin(5-HT3) 2.Dopamine(D2) 3.Opioid 4.Histamine 5.Muscarinic Types of Vomitting are: 1.Morning sickness- Vomiting which is caused during pregnency is known as morning sickness. 2.Motion sickness Vomiting which is caused during travelling is known as motion sickness.

3. 3.Gastric sickness- The vomiting which is caused during stomach upset is known as gastric sickness. Pathophysiology of vomiting: 1.In medulla oblengeta the vomiting centre is present. 2.Vomiting is caused due to activation of vomiting centre . 3.Vomiting centre activates by three types- a.Self stimulation or direct activation. b.CTZ activates vomiting centre . c.NTS activates vomiting centre . 4.If GI irritation or any infection caused then prostaglandin and serotonin releases and activates NTS and CTZ and then vomiting centre activates. 5.Drugs like levodopa , morphin are responsible for releasing og histamine binds to H1 receptor and activates vomiing centre . Emetic agents- 1.Apomorphine Apomorphin is a synthetic derivative of morphine. It stimulates the D2 receptor in CTZ. It cause vomiting. Side effects – Higher dose produce vomiting and sedation and overdose causes Respiratory and cardic depression.

4. 2.Xylazine- Xylazine acts as aplha-2-adrenergic agonist. It is contraindicated in pregnency . 3. 3%Hydrogen Peroxide- Hydrogen peroxide produce emesis and causes esophagitis and gastrities . 4.Activated Charcoal- Activates charcoal is given orally to absorb toxins or drugs. Side effects – Constipation , Diarrhoea , Black faeces . Anti emetics- The agents which are used in treatment of emesis is known as anti emetics. Classification- 1.Anticholinergics- Hyoscine , Dicyclomine 2.D2 blockers- Chlorpromazine , Trichloropromazine 3.H1 antihistaminics - Promethazine , Diphenehydramine , Dimenhydrinate , Doxylamine , Meclizine.

5. 4. 5HT3 antagonist- Ondensetron , Ramosetron , Granisetron . 5. NK1 blockers- Aprepitant , Fosaprepitant . 6.Prokinetic drug- Metoclopramide , Domperidone , Cisapride . 7.Adjuvant antiemetics Dexamethasone , Dronabinol , Nabilone . 1.Anticholinergics- It blocks the nerve impulse conduction throough cholinergic linkage in pathway leading from vestibular apparatus in vomiting centre . Use – Used in motion sickness . Adverse effect- Sedation. 2. H1 Antihistaminics - It prevents emesis by bolcking impulses from vestibular apparatus to CTZ. Use-Prevention of emesis. Adverse effect-Dryness of mouth and sedation.

6. 3. 5-HT3 Receptor Antagonist – It acts by blocking serotonin receptor which prevent emesis. Use- Anti emetic or to prevent emesis which is caused due to cancer therapy i.e. Chemotherapy. 4.Prokinetic- Eg . Metoclopramide- Metoclopramide shows an antiemetic effect by inhibiting Dopamine(D2) and serotonin (5-HT3) receptors in CTZ. Use- It is used as antiemetic. Adverse effects- Sedation , Dizziness , Diarrhoea , and Muscle dystonia. 5.NK1 blockers- NK1 blockers block NK1 receptor by preventing nausea and vomiting. Use-Prevention of acute and delayed nausea and vomiting in cancer chemotherapy.

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