The successful treatment of thallium sulfate toxicity in a dog using Prussian blue

Objective: Thallium sulfate, once commonly used as a household rodenticide, is a poisonous heavy metal banned in most countries due to its high toxicity. We report a case of thallium poisoning in a dog which was successfully treated using Prussian blue.

Case report: An 8 Kg, 5-year-old female miniature schnauzer was presented to a veterinary clinic four days after eating corn soaked in an old liquid rodenticide containing 5 g/L thallium sulfate. The maximum estimated ingested dose was 1.25 grams thallium sulfate (156 mg/Kg). The reported minimal lethal dose of thallium sulfate in dogs is 12-15 mg/Kg [1]. The dog presented with signs of lethargy, anorexia, ataxia, abdominal pain and hair loss. Treatment of thallium toxicity is most effective using a specific chelator, Prussian blue. Availability of this antidote can be problematic, especially in a veterinary setting. In the Netherlands Prussian blue (Radiogardase-CSVR , ferric hexacyanoferrate(II)) is available via the National emergency stock of antidotes, this stock is not for veterinary use. Fortunately, the stock of Prussian blue was close to its expiration date however, and therefore it was made available for this dog. The dog received a human dose of 250 mg/Kg Prussian blue per day for 15 days. Additional treatments included butylscopolamine bromide (BuscopanVR) as an antispasmodic to treat the abdominal pain, dexamethasone to aid the Buscopan injections, lactulose as a laxative (Prussian blue can cause obstipation), and four days of activated charcoal following the Prussian blue treatment. Over the course of the poisoning the alopecia progressed, most markedly over the abdominal area and around the muzzle. Furthermore, dermal lesions appeared primarily situated at the soles of the paws. Behaviourally, the dog became more withdrawn and irritable. Blood thallium concentrations were determined 9, 18, and 38 days after exposure and were 196 mg/L, 20 mg/L, and 21.5 mg/L, respectively. After approximately six to eight weeks hair began to grow back and behaviour started to normalize. Three months after the exposure the dog was completely recovered, without any sequelae.

Conclusion: To our knowledge this is the first documented case of a potentially severe thallium poisoning in a dog, successfully treated with Prussian blue. We propose that this treatment contributed significantly to the recovery of the dog. Our case demonstrates that, when available, Prussian blue can be safely administered to dogs to treat thallium toxicity.