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The usual suspects: Top 10 toxins poisonous to pets


These bad-boys of the toxicology world are dangerous to pets. Heres how to handle these cases.

Let's meet the usual suspects making up the list of the top 10 most common poisoning cases in dogs and cats, reported to Pet Poison Helpline.

1. Chocolate

All illustrations by Roxy Townsend.

The crime: Cases involving dogs put chocolate on the top of the list as the most common toxin managed by Pet Poison Helpline. Darker forms of chocolate contain more theobromine, the chemical compound that causes the toxicity, than milk chocolate and are therefore more dangerous to dogs. The amount of chocolate ingested in relation to the size of the dog is also key in assessing risk. Mild clinical signs such as vomiting, diarrhea, increased thirst and hyperactivity are expected with doses of theobromine > 20 mg/kg. At doses of 40 mg/kg theobromine and above, dogs can additionally develop tachycardia and arrhythmias. Tremors and seizures are possible at doses of 60 mg/kg theobromine and above.

The time: Chocolate is slowly absorbed, so clinical signs can be delayed. Typically, they will begin within 12 hours of ingestion and can last up to several days with large ingestions because of the long half-life of theobromine in dogs.

The treatment: Emesis induction can be performed up to six hours after ingestion, since chocolate is slowly absorbed by a dog's stomach. Because of enterohepatic recirculation and significant renal excretion, multiple doses of activated charcoal and intravenous (IV) fluids are useful components of therapy. Treatment is otherwise symptomatic and supportive with antiemetics for vomiting, sedation for agitation and hyperactivity, beta blockers for tachycardia, antiarrhythmics, methocarbamol for tremors, and anticonvulsants if seizures develop.

2. Rodenticides

There are three main types of rodenticides on the market today: anticoagulants, bromethalin and cholecalciferol.

Anticoagulant rodenticides (chlorophacinone, diphacinone, brodifacoum, warfarin)

The crime: Anticoagulant rodenticides interfere with the body's ability to produce vitamin K-dependent clotting factors and can result in coagulopathy. The most common clinical signs of poisoning in pets include lethargy, inappetence, pallor, dyspnea, coughing and other signs of bleeding. The margin of safety for anticoagulant rodenticides varies depending on the active ingredient. Cats are resistant to the effects of these products compared with dogs and rarely develop toxicosis.

The time: Signs of poisoning typically occur three to five days after ingestion. Long-acting anticoagulant rodenticides have a long half-life, so treatment is usually needed for at least 28 days.

The treatment: In cases of poisoning, Vitamin K1 (phytonadione) is antidotal and is dosed at 2.5-5 mg/kg/day divided into two daily doses for 28 days. Oral Vitamin K1 is preferred over injectable when possible. A prothrombin time (PT) should be obtained 48 hours after treatment is complete to ensure proper duration of treatment. In cases of active bleeding, transfusion may also be necessary.


The crime: Bromethalin rodenticides cause cerebral edema and resultant neurologic signs when ingested in toxic amounts by pets. The minimum lethal dose in cats is reported to be ~ 0.25 mg/kg, rendering them much more sensitive than dogs, whose minimum lethal dose ranges from 0.95-1.05 mg/kg. Signs of toxicosis include central nervous system (CNS) depression, ataxia, tremors, seizures, paresis/paralysis, hyperthermia, abnormal pupillary light reflexes (PLRs), anisocoria, nystagmus and coma.

The time: Clinical signs typically begin within 24 hours for high dose ingestions but may be delayed up to two to five days after ingestion with lower dose ingestions. The clinical signs may last for weeks, and some pets may be left with permanent neurologic impairment.

The treatment: As there is no antidote for bromethalin, prompt gastrointestinal (GI) decontamination with emesis induction and multiple doses of activated charcoal are key. If clinical signs develop, treatment includes supportive and symptomatic care, including mannitol for cerebral edema, nursing care, anticonvulsants for seizures, and methocarbamol for tremors.

Cholecalciferol is a vitamin D type of rodent bait and will be covered under the vitamin D section below.


3. Ibuprofen (Advil)

The crime: Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) ubiquitous in most homes. In healthy dogs, GI ulceration can occur with acute doses > 25 mg/kg; renal injury can occur at doses > 100 mg/kg. In healthy cats, GI ulceration is possible at > 12 mg/kg and renal injury at > 50 mg/kg. It's important to remember that signs are possible at lower doses with very young, old, or disease-compromised pets.

Common clinical signs include vomiting with or without blood, melena, inappetence, lethargy, GI ulceration and renal failure. Very high doses can also lead to development of decreased mentation, coma and seizures.

The time: GI signs usually develop within 12 hours, and renal failure can develop within 24 to 48 hours of ingestion.

The treatment: Ibuprofen is rapidly absorbed, but emesis induction can be performed within two hours of ingestion. Ibuprofen undergoes enterohepatic circulation and warrants repeated doses of activated charcoal, especially for ingestions carrying a risk of renal injury. GI protectants should be prescribed for seven to 10 days. Additional therapy is required for ingestions with a potential for renal injury. IV fluids for 48 plus hours will help provide renal protection and hydration support. Lab work should be monitored during treatment.

4. Xylitol

The crime: Xylitol is a type of sugar alcohol used in sugar-free gums, dental products, foods, supplements and other products. Hypoglycemia can occur at doses > 0.1 g/kg xylitol, and hepatic injury is possible at doses > 0.5 g/kg xylitol in dogs. Cats do not seem to be a species sensitive to xylitol. Clinical signs of xylitol poisoning are dose dependent. Vomiting is a frequent early sign. Hypoglycemia can result in CNS depression, ataxia, recumbency, tremors and seizures. Hepatic necrosis can cause elevations in serum alanine transaminase (ALT) and bilirubin, vomiting, lethargy, anorexia, icterus and coagulopathy.

The time: Hypoglycemia develops rapidly within six hours of ingestion and can last up to 24 to 48 hours. Elevated liver enzyme activities develop within 12 to 48 hours, will begin to improve within the first week, and usually normalize by four weeks after ingestion.

The treatment: Emesis can be induced once normoglycemia is confirmed. Activated charcoal is not effective in cases of xylitol poisoning. If a hypoglycemic dose is ingested, monitor blood glucose and initiate parenteral dextrose supplementation if hypoglycemia develops. If a liver toxic dose is ingested, additional treatment will be needed. Preemptive dextrose supplementation, even in normoglycemic patients, may help mitigate the risk of hepatic necrosis. Initiate treatment with oral hepatoprotectants, such as SAM-e. N-acetylcysteine can also be started if a patient has ingested a very high dose or if liver enzymes begin to elevate.


5. Grapes and raisins

The crime: Grape and raisin toxicosis in dogs can result in kidney failure, is thought to be idiosyncratic, and has no reliable toxic dose.

The time: Vomiting usually develops as an early clinical sign within 24 hours, and renal failure develops within 24 to 48 hours.

The treatment: Emesis induction can be performed up to six hours after ingestion due to delayed gastric emptying. Follow with one dose of activated charcoal, IV fluids for 48-plus hours, symptomatic care with antiemetics for any vomiting, and monitoring of renal values.

6. Antidepressants (Prozac, Paxil, Effexor, Cymbalta)

The crime: Overdose of antidepressant drugs can lead to serious clinical signs of serotonin syndrome, agitation versus lethargy, disorientation, vocalization, mydriasis, tremors, seizures and changes in heart rate and blood pressure. The toxic doses of these drugs vary by drug and species but can be estimated at about more than two to three times the therapeutic dose.

The time: Clinical signs usually develop within four hours if a pet was exposed to a regular release drug formulation but can be delayed up to eight hours if an extended-release formulation was ingested. The clinical signs usually last 24 to 48 hours and occasionally longer with some extended-release drugs.

The treatment: Emesis induction is appropriate with a recent exposure but should be avoided in symptomatic patients. Activated charcoal may be administered as long as aspiration risk is considered low. IV fluid therapy is used for hydration and perfusion, sedation for signs of agitation and cyproheptadine for its anti-serotonin effects.


7. Acetaminophen (Tylenol)

The crime: Acetaminophen is a common human pain medication that can cause serious poisoning when ingested by pets. Dogs that ingest overdoses of acetaminophen primarily develop hepatic toxicosis, which is possible at doses > 100 mg/kg. Signs may include liver enzyme elevations, depression, anorexia, vomiting, abdominal pain and methemoglobinemia with high doses. Cats are especially sensitive to acetaminophen due to a decreased ability to metabolize this drug and may show signs at doses as low as 10 mg/kg. Clinical signs may include anorexia, lethargy, salivation, vomiting, edema of the face and paws, respiratory distress and cyanosis.

The time: Cats develop clinical signs rapidly within hours of ingestion. GI signs may develop early in dogs, and liver failure can occur within 24 to 48 hours of ingestion.

The treatment: Acetaminophen is rapidly absorbed, but emesis induction can be performed within two hours of ingestion. N-acetylcysteine is the antidote for acetaminophen and is given at a loading dose of 140 mg/kg orally or intravenously, followed by 70 mg/kg every six hours for seven to eight treatments or up to 17 doses if there are signs. Other hepatoprotectant drugs, such as SAM-e, can be helpful, and IV crystalloids should be provided for hemodynamic support.

8. Vitamin D and cholecalciferol

The crime: Human vitamin D supplements and cholecalciferol rodenticides can lead to hypercalcemia and renal failure when ingested in excess by pets. The minimum toxic dose for vitamin D3 is 0.1 mg/kg, with a higher likelihood of hypercalcemia leading to tissue mineralization with doses > 0.5 mg/kg. Early signs of poisoning include vomiting, depression, anorexia, diarrhea, polyuria with later development of hypercalcemia, hyperphosphatemia and nephropathy.

The time: Clinical signs of GI upset often occur within the first 24 hours after ingestion, and hypercalcemia may be delayed up to 18 to 72 hours after ingestion. If hypercalcemia develops, treatment and monitoring may be needed for several weeks because of the long half-life of cholecalciferol.

The treatment: Emesis induction is appropriate with a recent exposure, followed by multiple doses of activated charcoal over the first 24 hours after ingestion. Cholestyramine may be given between charcoal doses to decrease enterohepatic reabsorption of this toxin. Close monitoring of lab work is necessary. If hypercalcemia develops, IV fluids may be used to increase calciuresis and prevent dehydration. Additional treatment for hypercalcemia includes bisphosphonates, furosemide and prednisone.


9. ADHD stimulant drugs (Adderall, Ritalin, Vyvanse)

The crime: Stimulant medications prescribed for ADHD in people can cause serious clinical signs when ingested by pets. The toxic dose varies by specific drug and species, but signs are expected to develop with ingestion of approximately 1 mg/kg for most drugs in this class. Signs of overdose include agitation, vocalization, hyperactivity, mydriasis, hypertension, tachycardia, hyperthermia, tremors and seizures.

The time: Clinical signs typically develop within several hours with most drugs in this category. They may last 24 hours or up to several days with extended-release formulations.

The treatment: Emesis induction is appropriate with a recent exposure but should be avoided in symptomatic patients. Activated charcoal may be administered as long as aspiration risk is considered low. IV fluid therapy is used for hydration and perfusion. Agitation is treated with sedation, and acepromazine is used most commonly. Anticonvulsants and methocarbamol may be administered if seizures and tremors occur.

10. Fertilizers

The crime: Fortunately, most ready-to-use yard and garden fertilizers have a low risk of poisoning when ingested by pets and usually result in only vomiting and diarrhea. Sewage sludge-based fertilizers, such as Milorganite, carry an increased risk of GI signs and can also cause self-limiting muscle pain and stiffness.

The time: Clinical signs usually develop within 12 hours of ingestion and resolve within 24 hours.

The treatment: Treatment is symptomatic and supportive with fluids, antiemetics and analgesia as needed. Small ingestions often do not require any treatment as signs are mild and self-limiting.

Suggested reading:

1. Hovda LR, Brutlag A, Poppenga R, et al. Blackwell's Five Minute Clinical Companion Small Animal Toxicology, 2nd ed. Ames, Iowa: Wiley-Blackwell, 2016.

2. Peterson, ME, Talcott, PA. Small Animal Toxicology, 3rd ed. St. Louis, Missouri: Elsevier Saunders, 2013.

3. Plumlee, KH. Clinical Veterinary Toxicology; St. Louis, Missouri: Mosby, Inc, 2004.

4. Schmid RD, Hovda LR. Acute hepatic failure in a dog after xylitol ingestion. J Med Toxicol 2015;12;201-205.

5. Stern LA, Schnell M. Management of attention-deficit disorder and attention-deficit/hyperactivity disorder drug intoxication in dogs and cats. Vet Clin North Am Small Anim Pract 2012;42(2):279-287.

6. Thomas DE, Lee JA, Hovda LR. Retrospective evaluation of toxicosis from selective serotonin reuptake inhibitor antidepressants: 313 dogs (2005-2010). J Vet Emerg Crit Care 2012;22:674-681.

Charlotte Flint, DVM, DABT, is the senior consulting veterinarian, clinical toxicology, for Pet Poison Helpline.

About Pet Poison Helpline:

Pet Poison Helpline is an animal poison control center available 24/7 to pet owners and veterinary professionals seeking expert assistance with a potentially poisoned pet. Treatment advice is available for all species, including dogs, cats, birds, small mammals, large animals and exotic species. Pet Poison Helpline is available in North America by calling (800) 213-6680. Additional information can be found online at www.petpoisonhelpline.com.

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