Emetics
Emetics are agents that induce vomiting and are utilized in specific medical situations, primarily to remove toxic substances from the stomach before they can be absorbed into the bloodstream.
The use of emetics is based on the principle of activating the body's natural vomiting reflex, a complex protective mechanism involving the central nervous system and 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.
Copper sulfate (CuSO4):
Preparation:
Copper sulfate can be prepared by reacting copper metal with hot concentrated sulfuric acid or by reacting copper oxide with dilute sulfuric acid.
The chemical reactions are as follows:
Cu + 2 H2SO4 → CuSO4 + SO2 + 2 H2O (with concentrated sulfuric acid)
CuO + H2SO4 → CuSO4 + H2O (with dilute sulfuric acid)
Properties:
Copper sulfate is a blue crystalline solid when hydrated (CuSO4·5H2O) and a white powder when anhydrous (CuSO4).
It is soluble in water and has a slightly acidic taste.
CuSO4 is an ionic compound and has a melting point of 110°C (230°F) for the pentahydrate form.
It is a strong oxidizing agent and can cause a reaction with many reducing agents.
Uses:
Copper sulfate is used as a fungicide and algaecide to control plant diseases and algae growth in bodies of water.
It finds applications in the textile and leather industries for dyeing and tanning processes.
CuSO4 is used in electroplating and as a catalyst in various chemical reactions.
Historically, it was used as an emetic, but this use is not recommended anymore due to its high toxicity.
Storage:
Copper sulfate should be stored in a cool, dry place, away from heat and direct sunlight.
It should be kept in a tightly closed container to minimize exposure to air and moisture.
Store CuSO4 away from strong reducing agents, acids, and flammable materials to prevent chemical reactions.
Assay
An assay of copper sulfate (CuSO4) typically involves a complexometric titration using ethylenediaminetetraacetic acid (EDTA) as the titrant.
In short, the process can be summarized as follows:
Prepare a standard EDTA solution of known concentration.
Accurately weigh a sample of copper sulfate and dissolve it in distilled water.
Add ammonium buffer solution (a mixture of ammonium chloride and ammonium hydroxide) to the copper sulfate sample to adjust the pH to around 9-10. At this pH, the Cu2+ ions form a stable complex with the EDTA.
Add a few drops of murexide indicator, which forms a wine-red color in the presence of free Cu2+ ions.
Titrate the copper sulfate solution with the standardized EDTA solution.
The copper ions will react with the EDTA, forming a stable copper-EDTA complex.
Continue adding EDTA until the color changes from wine-red to blue-violet, indicating the endpoint has been reached.
Calculate the concentration of copper sulfate in the sample using the volume of titrant used and the known concentration of the EDTA solution.
Sodium potassium tartrate (Rochelle salt, NaKC4H4O6·4H2O):
Preparation:
Sodium potassium tartrate can be prepared by neutralizing a mixture of tartaric acid with equimolar amounts of sodium hydroxide and potassium hydroxide.
The chemical reaction is as follows:
C4H6O6 + NaOH + KOH → NaKC4H4O6 + 2 H2O
Properties:
Sodium potassium tartrate is a colorless crystalline solid.
It is soluble in water and has a mildly sweet, tart taste.
NaKC4H4O6·4H2O is a non-toxic, biodegradable compound.
It is hygroscopic, meaning it readily absorbs moisture from the air.
Uses:
Sodium potassium tartrate is used as a complexing agent in various analytical chemistry applications, such as Fehling's solution for the determination of reducing sugars.
It finds applications in the food industry as a stabilizer and emulsifier.
NaKC4H4O6 is used in the electroplating industry and as a component in some piezoelectric materials.
It can also be used as a mild laxative.
Storage:
Sodium potassium tartrate should be stored in a cool, dry place, away from heat and direct sunlight.
It should be kept in a tightly closed container to minimize exposure to air and moisture.
Store NaKC4H4O6 away from strong acids and oxidizing agents to prevent chemical reactions.