Pages

  • Home
  • Write for Us
  • Hire Us
  • Ask Us
  • Contact Us

Monday, October 3, 2011

Treatment of vomiting:

Treatment of vomiting varies with its cause, which can be found out by looking at the patient’s clinical presentation.

Reversible causes of vomiting such as hypercalcemia, constipation should be treated accordingly.
If vomiting is caused by a particular drug then that drug should be stopped if possible.

Antiemetic drugs can be given once the probable cause is found out. This is because the receptors that lead to vomiting vary with the cause, eg dopamine receptors in the chemoreceptor trigger zone are stimulated by metabolic and drug causes of nausea and vomiting, whereas gastric irritation stimulates histamine receptors in the vomiting centre via the vagus nerve. So based on the receptors activated, the antiemetic drugs are prescribed.




Classification of Antiemetic agents:

Before prescribing any of the antiemetic agents it is important to find out the cause of vomiting and the type of receptors involved. Combination of antiemetic agents with different mechanism of actions are often used especially in patients with vomiting due to drugs.


Antiemetic agents
Used to prevent nausea & vomiting due to:
1. Seretonin 5 HT3 antagonists
·         Onadensetron
·         Granisetron
·         Dolasetron
·         Palonosetron
Chemotherapy  
Operation
Radiation

2. Corticosteroids
·         Dexamethasone
·         Methylprednisolone

Chemotherapy
3. Neurokinin receptor antagonists
·         Aprepitant
·         Fosaprepitant

Chemotherapy
4. Phenothiazines
·         Prochlorperazine
·         Promethazine
·         Thiethyperazine

Chemotherapy
Operation
Hyperemesis gravidarum
5. Butyrophenones
·         Droperidol
·         Heloperidol

Chemotherapy
6. Substituted Benzamines
·         Metoclopramide
·         Trimethobenzamide

Chemotherapy
7. H1 AntiHistamines & Anticholinergic drugs
·         Diphenhydramine
·         Dimenhydrinate
·         Meclizine
·         Hyoscine

Chemotherapy
Operation
Motion sickness
8. Benzodiazepines
·         Lorazepam
·         Diazepam

Anticipatory vomiting
Anxiety
9. Cannabinoids
·         Dronabinol
·         Nabilone

Chemotherapy

Table: Anti-emetic drugs

Note: Need ORS packet? Clik here to know how to make one or
Click the link to buy Adventure Medical Oral Rehydration Salts (ORS) from Amazon.







Adverse / Side effects of antiemetics:

1. Drowsiness

2. Anti-muscarinic effects (atropine like side effects):

·         Dry mouth
·         Blurred vision
·         Constipation
·         Urinary retention

3. Gynaecomastia, Galactorrhoea (D2 receptor antagonist)

4. CNS disturbances like Somnolence

5. Sedation (Droperidol, Diphenhydramine)

6. Cardiac arrhythmias (Droperidol)


Reference: The following books were used in the making of the above article:






If you enjoyed this article and found it useful then please subscribe to my feeds via RSS or E-mail, and kindly take 5 minutes to share this article with everyone by clicking the share this button below. Thank you!

Clinical presentation of a case of vomiting:

The clinical presentation of vomiting varies with the cause. This is because the receptors that lead to vomiting vary with the cause, eg dopamine receptors in the chemoreceptor trigger zone are stimulated by metabolic and drug causes of nausea and vomiting, whereas gastric irritation stimulates histamine receptors in the vomiting centre via the vagus nerve.

So based on the receptors activated, the different types of antiemetic drugs are prescribed.

How does vomiting occur / Mechanism of vomiting?

In the brain(within the lateral medullary reticular formation of the brain stem), there is an area called Vomiting Center (nucleus of tractus solitarius), which controls vomiting. This vomiting center gets stimulated by different stimulus, eg gastric irritation, drugs (see causes of vomiting). The vomiting center then sends signals to the gastrointestinal tract and other areas which ultimately leads to vomiting.



As you can see in the figure above, there are four main sites from where the different stimuli come from:

1. Chemoreceptor trigger zone / Area postrema: stimulated by emetogenic stimuli (eg toxins) in blood or cerebrospinal fluid (CSF).
2. Vestibular system: stimulated by disturbances in the balancing system of the body eg motion sickness
3. Gastrointestinal tract and heart: Stimuled by substances that cause gastric irritation (drugs, acute infections, toxins, radiation, distension), myocardial infarction.
4. Central nervous system: stimulated by psychiatric disoreders, stress, anticipatory vomiting prior to cancer treatment or surgery.

The different emetogenic stimuli acts through different receptors. These receptors vary in different sites. The activation of different receptors depends on the cause or causes of vomiting and nausea. Based on these receptors the different classed of anti-emetic drugs are prescribed.

Receptors associated with vomiting:

Zone
Vomiting center
Chemoreceptor trigger zone / Area Postrema
Vestibular system
Gastrointestinal tract and heart
Central nervous system
Receptors(R)
· Histamine 1 (H1)
· Muscarinic 1 (M1)
· Neurokinin 1 (NK1)
· 5-HT3
· Dopamine D2
· Opioid
· Seretonin 5-HT3
· Neurokinin 1 (NK1)
· Muscarinic M1
· Histamine H1
· 5 HT3
· Mechano-R
· Chemo-R
No receptors. But stimulates through areas like cortex, thalamus, hypothalamus, meninges

The diagram below describes the whole process of vomiting in brief:

What is Nausea and vomiting?

Nausea is the sensation of feeling sick. 

Vomiting is the forceful expulsion of gastric content via the mouth. It is a complex reflex mechanism which involves both autonomic and somatic neural pathways. 

Both nausea and vomiting are associated with pallor, sweating and hyperventilation.