Toxicology Brief: Mushroom poisoning in dogs - Veterinary Medicine
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Toxicology Brief: Mushroom poisoning in dogs


VETERINARY MEDICINE


There are three distinct sequential phases of cyclopeptide poisoning. The initial gastroenteritis phase is characterized by profuse bloody diarrhea, vomiting, nausea, abdominal pain, dehydration, electrolyte imbalance, fever, tachycardia, and hyperglycemia.9 This phase typically lasts about 24 hours. The resolution of clinical signs and subclinical elevations of serum alanine transaminase and aspartate transaminase activities characterize the onset of the 12- to 24-hour latent phase.9 The final—and often terminal—hepatorenal phase of poisoning begins three to four days after ingestion.9 Severe hepatic dysfunction, severe renal failure, cerebral edema, icterus, elevated serum hepatic enzyme activities, hypoglycemia, coagulopathies and hemorrhage, azotemia, metabolic acidosis, and sepsis characterize the hepatorenal phase. In addition, neurologic dysfunction including hepatic encephalopathy and coma can occur.9 Typically, the animal dies three to seven days after ingestion.9

Treatment. Early aggressive decontamination and enhanced elimination are critical.6,8,9 Performing emergency upper GI decontamination (inducing emesis or gastric lavage) is probably not beneficial more than four hours after ingestion since phallotoxins and amatoxins are rapidly absorbed from the GI tract and do not form gastric concretions or delay gastric emptying.9 Induce emesis only in asymptomatic animals because of the risks associated with this procedure.

The effectiveness of activated charcoal is unknown, but its use has been recommended.9 Administer an activated charcoal slurry (1 g/5 ml water) orally at a dose of 2 to 5 ml/kg in combination with a mild cathartic (sorbitol 3 mg/kg orally).11 Repeated doses of activated charcoal may be administered every four to six hours in an attempt to reduce the enterohepatic circulation of amatoxins and may be of value up to 48 hours after ingestion.9 Adequately hydrate patients treated with multiple doses of activated charcoal to prevent constipation.11 Repeated doses of sorbitol may cause marked hypotension or hypovolemic shock, particularly in patients with underlying cardiovascular problems or in small patients, so monitoring is required if repeated doses of activated charcoal and sorbitol are administered.11

Enhanced elimination using peritoneal dialysis and other methods of extracorporeal elimination has yielded occasional therapeutic successes in people.6,9 Administering parenteral penicillin G benzathine at doses greater than 4,300 U/kg, which displaces amatoxins from plasma protein-binding sites making them more available for renal excretion, has been claimed to improve survival in people.9 However, a recent 20-year retrospective analysis has demonstrated that this treatment, alone or in combination with other agents, has little efficacy.12

Supportive care involves administering intravenous crystalloids, glucose, fresh frozen plasma, GI protectants (e.g. kaolin/pectin 1 to 2 ml/kg orally every six to 12 hours), and broad-spectrum parenteral antibiotics to reduce the risk of sepsis. Oral supplementation or parenteral treatment with vitamin K1 (2.5 to 5 mg/kg daily) and packed red blood cell or whole blood transfusions may be required if bleeding is severe.

Silibinin dihydrogen disuccinate disodium and acetylcysteine have been suggested as antidotes for cyclopeptide poisoning.9 Silibinin is a semisynthetic, commercialized, active derivative of silymarin, the hepatoprotectant and antioxidant mixture of medicinal flavonolignans derived from milk thistle (Silybum marianum). Administering silibinin intravenously (20 to 50 mg/kg/day in four doses) substantially increases the survival rate in people.9 Unfortunately, the injectable form of this antidote is not available in the United States, and the poor water solubility and bioavailability of silymarin may limit the effectiveness of this potential antidote when orally administered. Silipide, a complex of silymarin and phosphatidylcholine (lecithin), is about 10 times more bioavailable than silymarin, but its effectiveness as an oral antidote for A. phalloides mushroom poisoning has not been investigated. The effectiveness of acetylcysteine for treating mushroom cyclopeptide poisoning is questionable. However, given its low risk of adverse effects, treatment can be attempted by administering a loading dose of 140 mg/kg orally followed by 70 mg/kg orally every six hours for as long as the patient needs it based on clinical judgment.


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Source: VETERINARY MEDICINE,
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