Emetics are agents used to induce vomiting, primarily to remove toxic substances from the stomach before absorption into the bloodstream.
They work by activating the body's natural vomiting reflex, involving both the central nervous system and the gastrointestinal tract.
Mechanism of Action:
The process of vomiting, or emesis, is regulated by the brain's vomiting center, located in the medulla oblongata.
This center coordinates the actions necessary for vomiting and can be activated by various stimuli, including:
Direct irritation of the stomach or intestines.
Activation of the chemoreceptor trigger zone (CTZ), which can detect toxins in the blood and then signal the vomiting center.
Sensory input from the brain, such as sights, smells, or emotions that can trigger nausea and vomiting.
When activated, the vomiting center orchestrates a series of events: the lower esophageal sphincter relaxes, the diaphragm and abdominal muscles contract to increase intra-abdominal pressure, and the stomach contracts to expel its contents.
Common Emetics:
1. Ipecac Syrup:
Derived from the root of the ipecacuanha plant, it has been used historically for inducing vomiting in cases of poisoning.
Ipecac syrup acts locally by irritating the stomach lining and centrally by stimulating the CTZ.
Its use has significantly decreased due to concerns over safety and the potential for abuse, and it is no longer recommended for routine use in poisoning cases.
2. Apomorphine:
Unlike ipecac syrup, apomorphine acts centrally by stimulating dopamine receptors in the brain to induce vomiting.
It is administered subcutaneously or intravenously under medical supervision due to its potent effects and potential side effects, including respiratory depression and hypotension.
Considerations and Cautions:
The use of emetics is not universally recommended for all cases of poisoning. Certain considerations must be taken into account:
Nature of the Poison: Emetics are contraindicated if the substance ingested is caustic (such as acids or alkalis) or petroleum-based, as vomiting could cause additional damage to the esophagus or lungs.
Patient Condition: Emetics are not suitable for patients who are unconscious, convulsing, or otherwise unable to protect their airway, due to the risk of aspiration.