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Emetics and Anti-Emetic Drugs (view source)
Revision as of 14:47, 4 November 2008
, 14:47, 4 November 2008no edit summary
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==Emetics==
These drugs can be used to remove non-corrosive poisons from the stomac before any is absorbed. '''Charcoal''' can be given to adsorb as much poison as possible and decrease their absorption.
They act by:
'''Irritating the gastric mucosa''', the so called "Reflux Emetics". Examples are; magnesium sulphate (epsom salts), ipecacuanha, sodium chloride, sodium carbonate (washing soda), mustard.
'''Stimulating the Vomiting Centre in the Medulla''' These drugs act by agonising neurotransmitter receptors involved in emetic pathways; they are centrally acting emetics. '''Apomorphine''' is such a drug.
==Anti-Emetics==
Persistent vomiting is a potentially dangerous situation for an animal to be in. It can lead to dehydration, metabolic alkalosis and electrolyte imbalances; at worst it can lead to shock. If vomiting is occuring for a reason other than ingestion of a foreign material or a gastric obstruction, such as a drug side-effect, it may be worth considering using an anti-emetic.
It must be remebered that vomiting often can be controlled by withholding food, a change of diet and anthelmintic therapy and so they are only really needed if there is no improvement and the animal is becoming more ill.
===Dopamine 2 (D<sub>2</sub>) Receptor Agonists===
One class of drugs the '''phenothiazines''' inhibit unselectively M, H<sub>1</sub>, and alpha receptors as well as D<sub>2</sub> receptors. This means that they have additional effects, such as sedation and hypotension. These drugs are further discussed on the [[anaesthesia]] pages, but examples are '''acepromazine, chlorpromazine''' and '''proclorperazide'''.
'''Metoclopramide''' isn't a phenothiazine but also acts on the D<sub>2</sub> receptors, it also though works on serotonin receptor. It inhibits some serotonin receptors (5-HT<sub>3</sub>) and activates others (5-HT<sub>4</sub>). This results in reducing inputs into the vomiting center and also increases gastric emptying and gastrointestinal tract motility.
===5-HT<sub>3</sub> Receptor Antagonists===
An example is '''ondensetron''', which works by directly inhibiting the chemoreceptor trigger zone and thus inhibiting the vomiting centre.
===Muscarinic Receptor Antagonists===