Methylphenidate toxicosis in a cat.

A 10-year-old cat with restlessness, vocalizing, and circling was examined 13 hours after it was inadvertently given a 5-mg tablet of the CNS stimulant methylphenidate hydrochloride. Physical examination findings (generalized tremors, agitation, mydriasis, tachycardia, tachypnea, and hypertension) were consistent with overstimulation of the CNS and excessive adrenergic activity resulting from methylphenidate toxicosis. Plasma methylphenidate concentration at admission (83 ng/ml) was 5 to 16 times greater than the concentration reported to provide therapeutic effect in human beings. The cat was placed in a dark, padded cage to minimize external stimuli, and supportive care consisting of fluids and diazepam were administered. Clinical signs resolved within 25 hours after ingestion of methylphenidate.