Emetics

EMETICS

These are drugs used to evoke vomiting.

1. Act on CTZ : Apomorphine

2. Act reflexly and on CTZ : Ipecacuanha

Vomiting needs to be induced only when an undesirable substance (poison) has been ingested. Powdered mustard suspension or strong salts solution may be used in emergency. They act reflexly by irritating the stomach.

Apomorphine

It is a semisynthetic derivative of morphine; acts as a dopaminergic agonist on the CTZ. Injected i.m./s.c. in a dose of 6 mg, it promptly (within 5 min) induces vomiting. It should not be used if respiration is depressed, because it has inherent respiratory and CNS depressant actions. Oral use of apomorphine is not recommended because the emetic dose is larger, slow to act and rather inconsistent in action.

Apomorphine has a therapeutic effect in parkinsonism, but is not used due to side effects.

Ipecacuanha

The dried root of Cephaelis ipecacuanha contains emetine and is used as syrup ipecac (15–30 ml in adults, 10–15 ml in children, 5 ml in infants) for inducing vomiting. It should be available in every household for emergency use. It is less dependable than parenteral apomorphine and takes 15 min or more for the effect, but is safer. It acts by irritating gastric mucosa as well as through CTZ.

All emetics are contraindicated in:

·     Corrosive (acid, alkali) poisoning: risk of perforation and more injury to esophageal mucosa.

·         CNS stimulant drug poisoning: convulsions may be precipitated.

·   Kerosine (petroleum) poisoning: chances of aspiration of the liquid (due to low viscosity) and chemical pneumonia are high.

·         Unconscious patient: may aspirate the vomitus, because laryngeal reflex is likely to be impaired.

·           Morphine or phenothiazine poisoning: emetics are ineffective.