Cholinergic crisis after neostigmine administration in a dog with acquired focal myasthenia gravis

To describe the presentation and successful management of a dog experiencing a cholinergic crisis after neostigmine administration.

An 18-month-old neutered male Maltese-crossbred dog was diagnosed with acquired focal myasthenia gravis based on history and clinical signs of dysphagia and regurgitation, multiple series of thoracic radiographs showing focal to generalized megaesophagus, and an increased acetylcholine receptor antibody titer. After this diagnosis, the dog was initially treated with a single oral dose of pyridostigmine and later injectable neostigmine due to difficulty swallowing. Within 15 minutes of receiving a single dose (0.05 mg/kg) of subcutaneous neostigmine, the dog began showing muscarinic cholinergic signs of salivation and defecation, which progressed to nicotinic cholinergic signs of weakness and tachypnea. Within 30 minutes the dog experienced respiratory arrest and required ventilation. After 16 hours of ventilation, the dog recovered uneventfully and subsequently achieved a clinical and serologic remission from myasthenia gravis without further treatment.

Cholinergic crisis and differentiation from a myasthenic crisis is described in the human literature. This case represents the first report in the veterinary literature of a cholinergic crisis in a dog treated with neostigmine.