At initial examination, certain immediate, lifesaving measures could be needed. In general, treatment for toxicosis centers on three basic principles: prevention of further absorption, supportive care, and specific antidotes.
Prevention of Further Absorption of Toxic Agents in Animals
Decontamination for topically absorbed toxic agents usually can be achieved by thorough washing with liquid degreasing dish soap and water; clipping of the hair or wool might be necessary.
In cases of ingestion, emesis is generally of value in dogs, cats, and pigs if induced within a few hours of the exposure; however, the timing can vary substantially depending on the toxic agent. Emesis is contraindicated when the swallowing reflex is absent; the patient is not neurologically stable; the ingested substances are corrosive agents, volatile hydrocarbons, or petroleum distillates; or the risk of aspiration pneumonia is high.
Additional considerations for induction of emesis include the following:
For dogs:
Hydrogen peroxide (3% solution, 1–2 mL/kg, PO, up to 45 mL) is a gastric irritant and oral emetic that can be used in dogs only and when veterinary care or prescription options are not available.
D2-dopaminergic receptors in the chemoreceptor trigger zone (CRTZ) are important in mediating humoral emesis in dogs, making dopaminergic receptor agonists (eg, apomorphine) more effective and reliable emetics in dogs than in cats.
Apomorphine can be administered to dogs parenterally at a dosage of 0.04 mg/kg, IM, or 0.03 mg/kg, IV. Apomorphine tablets are available in some countries for insertion into the conjunctival sac or for sublingual administration; apomorphine should not be administered orally, because of negligible oral bioavailability and high first-pass metabolism.
Ropinirole, a dopaminergic receptor agonist, is also available for dogs and dosed as eye drops at 2.7–5.4 mg/m2 dropwise in the conjunctival sac; the same dose can be repeated once 20 minutes later, if the initial dose does not produce emesis. For conversion factors to determine body surface area from weight, see the table Weight to Body Surface Area Conversion for Dogs.
For cats:
Hydrogen peroxide, apomorphine, and ropinirole should not be used. Alpha-adrenergic receptors in the CRTZ are important for inducing emesis in cats, making alpha-2 adrenergic receptor agonists (eg, xylazine) more potent emetics in cats than in dogs.
Emesis induction in cats can be attempted with xylazine (0.44 mg/kg, IM) or dexmedetomidine (5–10 mcg/kg, IM or SC); hydromorphone (0.1 mg/kg, SC) is also a fairly effective emetic in cats.
The efficacy of emetics in cats is as low as 50%; therefore, decontamination by emesis can be a challenge in cats.
The excessive sedation or cardiovascular collapse that can occur with xylazine or dexmedetomidine can be reversed with yohimbine or atipamezole. Hydromorphone is generally more cardiac sparing, and signs of sedation can be reversed with naloxone if needed.
Inappropriate methods of decontamination include oral administration of salt or syrup of ipecac and forced vomiting by means of digital stimulation of the laryngeal region. Substances or solutions such as liquid dish soap, raw eggs, hot sauce, mustard, or similar substances are also contraindicated, and owners should be advised against their use.
Gastric lavage can be considered when emesis is not recommended or was unproductive, or when life-threatening clinical signs are present. However, effort and cost often outweigh reward, and gastric lavage should be considered only in extreme cases and done under appropriate sedation or general anesthesia with a protected airway. Gastric lavage is particularly relevant in species that do not vomit, such as horses and ruminants.
When the toxic agent cannot be physically removed via emesis or lavage, certain agents administered orally can adsorb the substance and minimize or prevent its absorption from the GI tract. Activated charcoal (1–2 g/kg, PO; may be repeated at 4- to 6-hour intervals as needed) effectively adsorbs a wide variety of compounds and usually is the adsorbent of choice for GI decontamination when toxicosis is suspected. Sorbitol, an osmotic cathartic, is often added to activated charcoal to decrease GI transit time and evacuate charcoal-bound toxic agents more rapidly.
Important considerations for administration of activated charcoal include the following:
For toxic agents that undergo enterohepatic recirculation, multidose activated charcoal can be indicated at a dosage of 1 g/kg of plain activated charcoal, PO, every 6–8 hours for 24 hours after exposure.
Hypernatremia is a risk with any activated charcoal administration, and that risk is increased with multiple doses. Therefore, the administration of activated charcoal should be limited to toxicosis cases involving toxic agents for which its benefit is known.
Pearls & Pitfalls
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Activated charcoal should not be used in animals with known hypersensitivity or allergy to it. With administration of high doses, vomiting, constipation, or diarrhea can occur, and feces will appear black. Contraindications to administering activated charcoal include the following:
ingestion of a caustic substance or hydrocarbon
planned endoscopy or abdominal surgery
risk for or suspected gastric or intestinal obstruction
high risk of aspiration pneumonia
severe dehydration
hypernatremia
hypovolemic shock
ileus
recent intestinal surgery
protracted vomiting
Cholestyramine is a bile acid–binding resin that enables toxic agents bound to bile to be excreted in the feces without being reabsorbed from the GI tract. Toxicoses due to certain toxic agents, including ibuprofen, carprofen, and vitamin D3 (cholecalciferol), can benefit from its use. Cholestyramine is dosed at 0.3–1 g/kg, PO, every 6 hours for 3 days for both dogs and cats. Before being administered to dogs, any cholestyramine product should be checked to make sure it does not contain xylitol.
Pearls & Pitfalls
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Intravenous lipid emulsion can be used to sequester certain lipophilic compounds, compartmentalizing so that less of the substance is available to tissues. Intralipid emulsion therapy is also considered to provide energy to myocytes, thus improving cardiac performance.
Not all clinically affected animals have shown a positive response to intralipid emulsion therapy, and animals with intoxication from certain substances, such as calcium channel blockers and bromethalin, have shown a worsening of clinical signs after the use of intravenous lipid emulsion.
Lipophilic toxicants with a high volume of distribution (Vd) often respond more favorably to intravenous lipid emulsion. Intravenous lipid emulsion is administered as a bolus at 1.5–4.0 mL/kg, IV, followed by 0.25 mL/kg/minute CRI for 30–60 minutes. Additional doses can be given as a bolus at 1.5 mL/kg, IV, every 6 hours if serum lipemia is not present.
Supportive Care for Toxicosis in Animals
Supportive care in cases of toxicosis is often necessary until the toxic agent can be metabolized and eliminated. The type of support required depends on the patient's condition and the toxic agent involved. Supportive efforts generally focus on control of neurological signs, maintenance of respiration, treatment for shock, correction of electrolyte imbalance and fluid loss, and control of cardiac dysfunction, as well as alleviation of pain.
Specific Antidotes for Toxicosis in Animals
Specific antidotes for various toxic agents work by various mechanisms.
Some antidotes complex with the compound (eg, oximes bind with organophosphorus insecticides, and EDTA chelates lead).
Some antidotes block or compete for receptor sites (eg, vitamin K competes with the receptor for anticoagulant rodenticides, and ethanol competes with ethylene glycol for alcohol dehydrogenase, limiting ethylene glycol's metabolism).
A few antidotes affect metabolism of the toxic agent (eg, nitrite and thiosulfate ions release and bind cyanide, and fomepizole inhibits alcohol dehydrogenase function, preventing metabolism of ethylene glycol).
Specific antidotes for food-producing animals have been limited; in the US, however, options are continually being considered by the FDA.
Key Points
Before initiating decontamination, the route of exposure and the substance type should be considered to ensure that the decontamination is appropriate and is unlikely to result in more harm.
Where possible, the use of antidotes should be considered early in the course of treatment after ingestion of a toxic substance.
Supportive care needs vary with the toxic agent and the status of the patient. Care should be continued until clinical signs have resolved.
For More Information
Peterson ME, Talcott PA, eds. Small Animal Toxicology. 3rd ed. Elsevier; 2013.
Gupta RC, ed. Veterinary Toxicology: Basic and Clinical Principles. 3rd ed. Elsevier; 2018.
Klaassen CD (ed.), Casarett LJ, Doull J. Casarett and Doull's Toxicology: The Basic Science of Poisons. 9th ed. McGraw-Hill; 2019.
Also see pet health content regarding general treatment of poisoning.
