GIT Lec 4 Pt 1 - Emetic Agents

Question 1

What is an emetic medication?

Answer 1

An emetic agent is a medication that induces nausea and vomiting.

Question 2

What are the indications of emetic medications?

Answer 2

We use emetic agents to get rid of most ingested poisons and toxins.

Question 3

What are the contraindications of emetic agents?

Answer 3

We use emetic agents for the removal of most ingested poisons, except in a few cases:
I. Corrosive chemicals: we don’t give emetic agents to patients who ingest corrosive, strong chemicals like strong acids and alkalis because they have the tendency to cause gastric perforations and thereby further esophageal damage.
II. CNS stimulating poisons: we don’t give emetic agents to patients who ingest CNS stimulating poisons since emesis can cause convulsions.
III. Kerosene or petrol derived furniture polish: since if we cause emesis, they can readily aspirate into the trachea and then lung causing chemical pneumonitis.
IV. Patients who are comatose, or are in a state of stupor or delirium, or in patients whose likelihood of aspirating the vomit is very high due to impaired protective mechanisms.

Question 4

How can we induce emesis?

Answer 4

A. Mechanically: vomiting can be induced by irritating the posterior pharynx.
B. Chemically: it can be induced by two mechanisms:
I. By stimulating the CTZ (chemo-receptor trigger zone) which then stimulates changes in the GIT that lead to vomiting by stimulating the vomiting center in the brain.
II. By stimulating the Vegal receptors in the GIT which directly stimulates the vomiting center without CTZ intervention.

Question 5

What are examples of emetic agents?

Answer 5

1. Apomorphine
2. Ipecacuahana (ipecac syrup)

Question 6

What are the characteristics of Apomorphine?

Answer 6

1. It is a semi-synthetic derivative of morphine.
2. MOA: it induces emesis by activating the D2 (dopamine) receptors in the CTZ, which then in turn activates the vomiting center which leads to emesis.
3. Indication: it is indicated in patients who are uncooperative (comatose for example)
4. ROA: it is ineffective orally so it has to be given subcutaneously or intramuscularly.
5. Dosage: 6mg for adults and 0.06mg/kg in children, it begins its action in 3-5 minutes. It is unstable in solution, so it should be prepared just prior to use.

Question 7

What are the characteristics of Ipecacuanha?

Answer 7

1. It is the most useful household emetic agent.
2. MOA: it works by both inducing local irritation on the GIT as well as affecting the CTZ.
3. The syrup can induce emesis even when the patient has taken anti-emetic medications, this is thought to be due to its local irritative action.
4. ROA: it can only be taken orally, so the patients have to be conscious and cooperative.
5. Dosage: 30ml solution in adults and children above 12, 15ml for children of 2 months til 12 years. Should be proceeded by drinking water. Emesis usually occurs within 15-30 minutes and it might not occur if the stomach is empty.
6. Side effects: it is capable of producing cardiac toxicity, however it has not been reported with normal therapeutic dosages.

Question 8

What are the chemo-transmitters responsible for inducing emesis?

Answer 8

1. Acetylcholine, acts on muscaranic (m) receptors.
2. Dopamine, acts on dopaminergic (D1 or D2) receptors.
3. Histamine, acts on histaminergic (H1) receptors.
4. 5-HT (serotonin), acts on 5-HT3 receptors.