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


Isoxazole derivatives

Amanita muscaria and Amanita pantherina are the principal North American mushroom species associated with poisoning from isoxazole derivatives.9 Given the popular recreational use of these mushrooms by people, it is surprising that poisoning in companion animals is poorly documented.9

Ibotenic acid and muscimol, the principal psychoactive isoxazole derivatives present in these mushrooms, alter visual perception rather than cause true hallucinations in people.9 Ibotenic acid, a CNS glutamate acid receptor agonist, acts as a CNS stimulant; muscimol, a CNS GABAB agonist, acts as a CNS depressant and sedative.9 In people, the primary effects are periods of CNS stimulation and depression that may alternate and may manifest as periods of manic excitement followed by periods of somnolence and deep sleep. Clinical signs typically associated with poisoning in people include dizziness, ataxia, euphoria, muscle twitches, and initial psychic stimulation followed by dream-filled sleep.9

Treatment. Treatment consists of upper GI decontamination and supportive measures, such as observation, confinement in a dark and quiet cage, and possibly sedation. Use all hypnotic drugs with caution because the isoxazole derivatives potentiate their effects.9

Psilocybin and psilocin

Because of its popularity as a recreational drug, this group of mushrooms, know as hallucinogenic or magic mushrooms, occasionally causes poisoning in dogs.3 Important genera involved in poisoning include Psilocybe, Panaeolus, Copelandia, Gymnopilus, Pluteus, and Conocybe.9 The principal toxins in these mushrooms are psilocybin and psilocin, which have LSD-like properties.9 These compounds typically produce a transient (less than 12-hour duration), dysphoric, and sympathomimetic syndrome. Coingestion of other drugs of abuse such as LSD, PCP, and marijuana is common in people and is a potentially important consideration in veterinary patients.9

Common clinical signs, which develop a half an hour to four hours after ingestion, include anxiety, aggression, disorientation, visual hallucinations (e.g. following and biting at imaginary flies, pointless barking), weakness, mydriasis, tachycardia, and hyperreflexia.3,9 Hypertension, hyperthermia, or convulsions may occur, and patients may become comatose in cases of extreme overdose. However, trauma caused by altered behavior is usually the greatest and most immediate threat to life.3,9

Treatment. Emergency GI decontamination in a conscious patient poisoned by these mushrooms may be difficult because of the patient's altered behavior and aggression. An easier option may be gastric lavage after anesthesia and placement of a cuffed endotracheal tube.9 The main potential difficulty associated with anesthesia is the induction because of the dysphoric, and potentially aggressive, mental state of the patient. Prior sedation with a benzodiazepine (0.5 to 1 mg/kg diazepam intravenously or 1 to 4 mg/kg rectally) or an alternative induction technique, such as using an induction chamber, may be required. The use of induction chambers carries with it the increased risks associated with decreased access to the patient, so their use with dysphoric patients requires careful clinical judgment.

Treatment usually consists of supportive care. Since the most immediate concern is preventing accidental trauma, often the most successful supportive care is placing the animal in a quiet, dark, padded cage in the presence of its owner.9 Warn the animal's owners and handlers of the potential for aggressive behavior. If sedation is required, a benzodiazepine (0.5 to 1 mg/kg diazepam intravenously or 1 to 4 mg/kg rectally) can be administered.


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