Emesis, CTZ, Emetics used in emesis, MCQS for GPAT, NEET PG, NIPER, Drug inspector and pharmacist exam.

Emesis: Vomiting is rarely painful, but never pleasant. Vomiting, also known scientifically as “emesis” and colloquially as throwing up, retching, heaving, or being sick, is the forcible voluntary or involuntary emptying of stomach contents through the mouth or, less often, the nose.

Vomiting occurs due to stimulation of the emetic (vomiting centre) situated in medulla oblongata. The chemoreceptor trigger zone (CTZ) located in the area postrema and the nucleus tractus solitarius (NTS) are the most important relay areas for afferent impulses arising in the g.i.t, throat and other viscera.

There are different types of vomiting. Some people get the dry heaves, where you retch and feel like vomiting, but nothing comes out of your stomach. The dry heaves are also called nonproductive emesis.

Blood streaked or bloody vomit usually indicates a cut or scrape to the esophagus or stomach. Some vomit resembles coffee grounds. Vomit that looks like coffee grounds occurs when stomach acids and blood congeal. Coffee ground vomit can be a sign of ulcer, GERD, cancer of the stomach or liver, or other abdominal conditions.

Yellow vomit indicates the presence of bile, which usually happens after a meal.

It’s rare, but people with abnormal intestinal function could possibly vomit up partially digested food or feces.

Sign and symptoms of emesis: 

Nausea and vomiting commonly occur in those with infections ranging from influenza to gastroentritis. Symptoms that occur with nausea and vomiting include:

• Abdominal pain
• Diarrhea
• Fever
• Lightheadedness
• Vertigo
• Rapid pulse
• Excessive sweating
• Dry mouth
• Decreased urination
• Chest pain
• Fainting
• Confusion
• Excessive sleepiness

Causes and risk factor of emesis:

Some people may also self-induce vomiting due to eating disorders. Vomiting is an involuntary reflex that empties the stomach forcefully

• Ingestion of toxins or excessive amounts of alcohol
• Migraine
• Labyrinthitis, which also causes dizziness and a feeling of spinning (vertigo).
• Motion sickness, nausea and vomiting associated with traveling
• Certain medicines, such as antibiotics and opioid painkillers
• Kidney infections and Kidney stones
• A blockage in your bowel, which may be caused by a hernia or gall stones
• Chemotherapy and radiotherapy
• An inflamed gallbladder
• Early stages of pregnancy
• Medication-induced vomiting
• Intense pain
• Emotional stress (such as fear)
• Gallbladder disease
• Food poisoning
• Infections (such as the “stomach flu”)
• Overeating
• A reaction to certain smells or odors
• Heart attack
•  Brain injury
• Brain tumor
• Ulcers
• Some forms of cancer

Classification of drugs for emesis (Emetics):

1. Act on CTZ- Apomorphine
2. Act reflexly and on CTZ- Ipecacuanha

A. Apomorphine: Apomorphine causes vomiting by acting on dopamine receptors in the chemoreceptor trigger zone of the medulla; this activates the nearby vomiting center. It should not be used if respiration is depressed, because it has inherent respiratory  and CNS depressant actions. Apomorphine is  also used in parkinsonism but is not used due to its side effects.

Side effects: 

• nausea.
• vomiting.
• constipation.
• diarrhea.
• headache.
• yawning.
• runny nose.
• weakness

B. Ipecacuanha: The emetic components of ipecac, emetine and cephaeline, act centrally and locally in the gastrointestinal tract to cause vomiting. The mechanism by which ipecac performs its effect by irritating the stomach lining and chemically stimulating the chemoreceptor trigger zone.

Phrmacokinetics: The main components of ipecac are rapidly absorbed from the GI tract, this absorption depends on the amount of emesis produced by the administered dose. The bioavailability of ipecac is reduced over time from 67-11% after 5-60 minutes of administration. The main components of ipecac have been shown in microsomal enzyme systems that emetine is converted to cephaeline and 9-O-demethylemetine by CYP2D6. On the other hand, CYP3A4 produces the transformation of emetine to 9-O-demethylemetine and 10-O-demethylemetine. Due to the emetic function, even 76% of the administered dose is vomited. From the absorbed dose, the elimination from plasma is relatively rapid. The effect of ipecac is done in about 20 minutes and the elimination of the little-absorbed dose is reported to be very rapid. Thus, the half-life is thought to be of about 0.5-1 hour.

Contraindications: All emetics are contraindicated in :

1. CNS stimulant drug poisoning: because convulsions may be precipitated
2. Corrosive (alkali, acid ) poisoning: there is risk of perforations and injury to esophageal mucosa.
3. Unconscious patient: may aspirate the vomitus because laryngeal reflex is ;likely to be impaired.
4. Kerosine (petroleum) poisoning: there is a risk of asipration of the liquid and chemical pneumonia.
5. Morphine or phenothiazine poisoning: because emetics may fail to act.

MCQs:

1. Forcible voluntary or involuntary emptying of stomach contents through the mouth or, less often, the nose is?

a. Diarrhoea

b. Costipation

c. Emesis

d. None of these

2. Emetic (vomiting centre) situated in which portion of brain?

a. Medulla oblongata

b. cerebrum

c. Cerebellum

d. None

3. Where is CTZ located?

a. Lungs

b. Kidney

c. Postrema

d. None

4. What are the sign and symptoms of emesis?

a. Abdominal pain

b. Diarrhea

c. Fever

d. All of above

5. What are the causes of emesis?

a. Kidney infections and Kidney stones

b. A blockage in your bowel, which may be caused by a hernia or gall stones

c. Chemotherapy and radiotherapy

d. All of above

6. Which drug act on CTZ?

a. Codeine

b. Morphine

c. Salbutamol

d. Apomorphine

7. Which drug act reflexly and on CTZ?

a. Ipecacuanha

b. Apomorphine

c. Sodium alginate

d. None of these

8. Which drug act on dopamine receptor?

a. Ipecacuanha

b. Apomorphine

c. a$b

d. None

9. Which drug is used in parkinson and for emesis?

    a. Ipecacuanha

b. Apomorphine

c. a & b

d. None

10. Side effects of apomorphine:

a. nausea.

b. vomiting.

c. constipation.

d. All of above

11. Emetine is converted to which form by CYP2D6?

a. Cephaeline

b. Ergotamine

c. Mercaptopurine

d. Methotrexate

12. There is risk of perforations and injury to esophageal mucosa in:

a. CNS stimulant drug poisoning

b. Corrosive (alkali, acid ) poisoning

c. Kerosine (petroleum) poisoning

d. Morphine or phenothiazine poisoning

13. There is a risk of asipration of the liquid and chemical pneumonia in.

a. CNS stimulant drug poisoning

b. Corrosive (alkali, acid ) poisoning

c. Kerosine (petroleum) poisoning

d. Morphine or phenothiazine poisoning

14. Emetics may fail to act in………………….

a. CNS stimulant drug poisoning

b. Corrosive (alkali, acid ) poisoning

c. Kerosine (petroleum) poisoning

d. Morphine or phenothiazine poisoning

15. The emetic components of ipecac, emetine and cephaeline, act centrally and locally in the:

a. G.I.T

b. Brain

c. Heart

d. Kidney

Answers:

1. c
2. a
3. c
4. d
5. d
6. d
7. a
8. b
9. b
10. d
11. a
12. b
13. c
14. d
15. a

References:

1. “K.D. Tripathi” emetics, page no : 709-710, 8th edition, june 2018.
2. “Medicine net”, oct 2019.
3. “Vallinda Riggins”, healthline, oct 2019.

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