Toxicology Brief: The 10 most common toxicoses in dogs - Veterinary Medicine
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Toxicology Brief: The 10 most common toxicoses in dogs


Thyroid hormones

Natural (desiccated thyroid) and synthetic (levothyroxine) derivatives of thyroid hormones are used to treat hypothyroidism in animals and people.

Dogs can maintain a remarkably normal physiologic state in the face of a massive L-thyroxine overdosage. Such resistance to developing thyrotoxicosis can be explained in part by pharmacokinetics, such as poor GI absorption, serum tri-iodothyronine (T3) and thyroxine (T4) being highly protein bound, alternative metabolic pathways, and greater potential for biliary excretion and fecal loss. In addition, certain organs (particularly the liver and kidneys) can concentrate thyroid hormones intracellularly, thereby rendering these hormones unavailable to bind to tissue receptors and induce a physiologic effect. Thus, the liver and kidneys can act as buffers by releasing small or large amounts of hormones, depending on what the body needs, back into the plasma. In an overdose situation, these buffer organs can concentrate the extra hormone and not release the already stored hormone.12

Dogs ingesting 0.2 mg/kg levothyroxine may develop mild signs, and dogs ingesting 1 mg/kg or more may need treatment. Hyperactivity and tachycardia are the most common signs of thyrotoxicosis.13

Initiate gastric decontamination procedures in patients that ingest a large dose, and monitor the patients' ECGs, blood pressures, and serum T4 concentrations. Treatment is symptomatic and supportive. Diazepam can be given to control hyperactivity, and beta-blockers can be given to control tachycardia.12


Regular household bleaches contain 3% to 6% sodium hypochlorite; commercial bleaches are typically much more concentrated. Color-safe bleaches contain sodium peroxide, sodium perborates, or enzymatic detergents. Most household bleaches are mild to moderate irritants and are not associated with a marked degree of tissue destruction. Household bleaches can cause skin or eye irritation, mild oral or esophageal burns, or GI irritation.14 Commercial bleaches can be corrosive and lead to severe stomatitis, pharyngitis, esophagitis, or esophageal ulcerations. Inhalation exposure to bleach can cause respiratory irritation, coughing, and bronchospasm. More serious damage can occur when bleach is mixed with ammonia-containing agents, forming chloramine and chlorine gases. Inhaling these gases can lead to a chemical pneumonitis.

To treat dermal exposure, bathe the dog with mild dishwashing detergent. The preferred initial treatment with bleach ingestion is oral dilution with milk or water. Dilution is most effective if it is performed early. Emesis is contraindicated because of the irritating properties of household bleach and the potential corrosive effects of commercial bleaches. GI protectants such as sucralfate or H2-blockers can also be used to symptomatically treat bleach ingestion. Treating corrosive damage may also require pain medications, antibiotics, and nutritional support. Oxygen and bronchodilators may be needed to treat respiratory signs in cases of inhalation exposure.


Fertilizer products generally contain varying amounts of nitrogen (N), phosphorus (P), and potassium (K) compounds. Product ingredients are often listed as N-P-K 10-8-8, where each number is the corresponding ingredient's concentration percentage. Fertilizer formulations include liquid, granular, and solid (e.g. stakes), and fertilizer additives may include herbicides, insecticides, fungicides, iron, copper, or zinc. Because fertilizers are usually a combination of ingredients, several toxic principles are possible. In general, the ingredients are poorly absorbed, and most of the signs are related to GI irritation.

Fertilizers have a wide margin of safety.15 GI signs such as vomiting, hypersalivation, diarrhea, or lethargy are common in dogs after ingesting fertilizers, especially ones with high percentages of phosphorus and potassium compounds. In most cases these signs are self-limiting and resolve within 12 to 24 hours. 15

Treat animals with GI signs supportively with antiemetics, fluids, and GI protectants. Address added insecticides or herbicides separately. Heavy metals, such as iron, are generally not bioavailable but can pose a hazard when dogs ingest large amounts.


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