Effective emetics and how to use them
Monday, November 21, 2011
Emetic agents work by causing gastric irritation, stimulating the CNS chemoreceptor trigger zone (CRTZ),1 or a combination of both. Many emetics work best if the pet has a small amount of food in its stomach. If the pet hasn’t eaten within the past two hours, a snack is recommended before administering emetics.1,2 Keep in mind that emetic agents are not effective if an anti-emetic (e.g., maropitant, ondansetron) has been recently administered to the patient.2
Here are the emetic agents effective for dogs:
Read the veterinarian-authored drug monograph on Apomorphine for veterinary use.
- Hydrogen peroxide (H2O2) irritates the oropharynx and gastric lining. This is the most commonly recommended emetic agent for pet owners attempting to induce vomiting in their dog at home.2 Use of hydrogen peroxide solutions in concentrations stronger than 3 percent can result in potential corrosive injury to the gastrointestinal (GI) mucosa.2 Potential side effects associated with the use of hydrogen peroxide are irritation to the gastrointestinal tract (GIT), hemorrhagic gastritis, gastric dilatation volvulus, and aspiration pneumonia.2 Hydrogen peroxide is not recommended for use in cats because it’s not a reliable emetic agent in cats, and approximately 25 percent of cats develop a hemorrhagic gastritis secondary to its use.2
- Apomorphine hydrochloride is a centrally-acting emetic agent that stimulates the CRTZ and quickly results in vomiting.2 This is most commonly used in veterinary clinics for inducing of vomiting in dogs, but it’s not recommended nor effective in cats.2 Side effects of administration of apomorphine include prolonged vomiting and ocular irritation (when administered subconjunctivally). This latter side effect can be limited with a thorough flushing of the subconjunctival sac.1 Apomorphine is contraindicated with ingestions of medications that can result in respiratory or CNS depression or with dopamine antagonist drugs that prevent vomiting.2
Emetic agents effective for cats are more limited, and there are no at-home emetic agents that should be recommended. The only recommended veterinary emetic is:
- Xylazine, an alpha-2 adrenergic agonist, is a centrally-acting emetic agent that’s effective when used in cats. Xylazine is not recommended for use in dogs, as it is not an effective emetic.2 Potential adverse effects with use of xylazine include bradycardia, sedation, tremors, and respiratory depression. Xylazine is contraindicated in medication ingestions that may result in an exacerbation or compounding of these potential side effects.1,2 In patients exhibiting persistent vomiting or excessive sedation from xylazine, the use of yohimbine or atipamezole can be used to reverse the effects.2
Alternative decontamination methods
Here are two alternative methods to consider if induction of vomiting is contraindicated for GI decontamination of your patient.
- Gastric lavage is recommended when the patient is unconscious, sedate, having tremors or seizures, as well as in situations where induction of vomiting has been unproductive. It’s also used with ingestions of substances (e.g., bone meal, or iron) that can result in bezoar formation or with large ingestions of medications that are approaching the LD50 or lethal dose for that medication.2 Gastric lavage is performed with the patient under anesthesia with an appropriately fitted endotracheal tube (to prevent aspiration) securely tied in place. Possible side effects or concerns with gastric lavage are the risk of aspiration pneumonia, the risks associated with sedation of a poisoned patient, and potential injury to the mouth, oropharynx, esophagus, or stomach.2 Gastric lavage should never be performed with ingestions of corrosive agents that increase the risk of gastric perforation, with ingestion of hydrocarbons (due to the high risk of aspiration pneumonia), or when sharp objects have been ingested.2
- Whole bowel irrigation is used to prevent absorption of ingested toxins by inducing a liquid stool through administration of large quantities of polyethylene glycol (PEG) electrolyte solution. Whole bowel irrigation typically needs to be continued for eight to 12 hours, until a clear effluent—fluid from the colon—is produced. Whole bowel irrigation is used with ingestion of toxic doses of iron, sustained-release medications,2 or enteric-coated medications. Possible complications of whole bowel irrigation are vomiting, bloating, abdominal discomfort, and possible aspiration pneumonia. Whole bowel irrigation should not be used with foreign body obstructions, ileus, perforated bowel, shock, vomiting, or GI hemorrhage.2
Harmful emetic agents
You should avoid recommending some emetic agents for your clients for “at home” vomiting induction. Here are three home remedies—often found on the Internet—that are often recommended but can potentially put the patient at further risk or harm.
- Syrup of ipecac has historically been recommended for use as an emetic agent but is no longer the standard of care in human or veterinary medicine, due to its cardiotoxic potential and tendency to result in prolonged vomiting, lethargy and diarrhea.2
- Digital vomiting induction (e.g., using your finger in the pet’s mouth to stimulate a gag reflex) can result in injury to both the patient and the owner.
- Soaps, mustard powder, and table salt are not reliable and they can result in further toxicity concerns (e.g., hypernatremia with the use of salt).2
Here’s how to use activated charcoal and cathartics in the poisoned patient.
Remember, obtaining a complete toxicology history and a thorough physical examination of the patient is always imperative before initiating any decontamination methods. This is to ensure that vomiting induction and administration of activated charcoal is warranted. When decontaminating a poisoned patient, the appropriate emetic agent should be used. When in doubt, a veterinarian or Pet Poison Helpline should always be consulted prior to decontamination to ensure a positive outcome for the poisoned patient.2
- Activated charcoal is used as an adsorbent and is the mainstay of most GI decontaminations. It may be used concomitantly with induction of vomiting or gastric lavage. Activated charcoal does not bind well with certain toxins and is not required or recommended with poisonings from heavy metals, alcohols (e.g., ethanol, ethanol, ethylene glycol), and xylitol.2 Activated charcoal may need to be administered multiple times with ingestions of extended-release or sustained-release medications or when the drug ingested undergoes enterohepatic recirculation in the liver (e.g., carprofen, ibuprofen).2 Activated charcoal shouldn’t be used in situations where abdominal surgery or endoscopic evaluations of the GIT may be needed; if there is evidence of intestinal obstructions, dehydration, or perforations of the GIT (e.g., corrosive ingestions); or with hydrocarbon ingestions.2
- Cathartics (e.g., sorbitol) are used to speed up the emptying of the GIT and decrease the time a toxicant is in the GIT where it can be re-absorbed.2 Cathartics are generally administered with the first dose of activated charcoal but discontinued with subsequent doses of activated charcoal. Repeat doses of cathartics may result in hypernatremia due to osmolality changes and free water loss into the GIT. Side effects of cathartic administration include vomiting, dehydration, abdominal cramping, hypernatremia, and possible hypotension.2
- Battaglia AM. Toxicologic Emergencies. In Battaglia AM, ed. Small Animal Emergency and Critical Care for Veterinary Technicians, 2nd Ed. St Louis: WB Saunders, 2007, pp 356-367.
- Lee JA. Decontamination of the Poisoned Patient. In: Osweiler G, Hovda L, Brutlag A, Lee JA, ed. Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Toxicology, 1st Ed. Iowa City: Wiley-Blackwell, 2010, pp. 5-19.
- Peterson ME. Toxicological Decontamination. In: Peterson ME, Talcott PA, ed. Small Animal Toxicology, 2nd Ed. St. Louis: Elsevier Saunders, 2006, pp. 127-141.
Veterinarians: Learn more about treating pet poison victims
Pet Poison Helpline has many critical resources on pet poisonings, some of which we've worked with Wedgewood Pharmacy to compile for you in one eBook. Download the eBook from the Resources for Veterinarians section of WedgewoodPetRx. Additionally, you can attend webinars for CE credit. Register for the next online presentation at PetPoisonHelpline.com. Pet Poison Helpline will be guest blogging here for a few weeks to share with you this important information on treating pet poisonings.
Justine Lee, DVM, DACVECC
Associate Director of Veterinary Services
Pet Poison Helpline
About Justine Lee, DVM:
Dr. Justine Lee is a board-certified emergency critical care veterinary specialist, and is currently the Associate Director of Veterinary Services for Pet Poison Helpline. For the previous five years, she was on faculty as an Assistant Clinical Professor at the University of Minnesota College of Veterinary Medicine.
Dr. Lee graduated from Virginia Tech with a BS in Animal Sciences, and then obtained her veterinary degree at Cornell University. She pursued her internship at Angell Memorial Animal Hospital, which is affiliated with the Massachusetts Society for the Prevention of Cruelty to Animals (MSPCA). In addition, she has also completed an emergency fellowship and residency at the University of Pennsylvania. Currently, she is 1 of approximately 450 board-certified veterinary specialists world wide in emergency and critical care, and is a Diplomate of the American College of Veterinary Emergency and Critical Care (DACVECC).
Dr. Lee has been published in numerous veterinary journals, including the Journal of American Veterinary Medical Association, the Journal of Veterinary Emergency Critical Care, and the Journal of Veterinary Internal Medicine. She is also the author of two humorous pet reference books entitled “It’s a Dog’s Life... but It’s Your Carpet” and “It’s a Cat’s World... You Just Live In It.” Dr. Lee lectures throughout the world on emergency and critical care, and recently was honored with the North American Veterinary Conference Small Animal Speaker of the Year award for 2011.
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11/21/2011 9:24:00 AM
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