Objective: To determine clinical signs and outcomes of methylphenidate hydrochloride (MPH) toxicosis in dogs; to assess effects of amount (ie, dose) and formulation (immediate or extended release) of ingested MPH on onset, duration, and severity of clinical signs; and to describe management of MPH intoxication.
Design: Retrospective case series.
Animals: 128 dogs with MPH toxicosis or exposure.
Procedures: Data from an Animal Poison Control Center (APCC) database from November 1, 2001, to November 30, 2008, were reviewed. Records of dogs were searched for APCC classifications of confirmed (n = 71) or suspected (39) MPH toxicosis; dogs (18) that ingested MPH but did not develop clinical signs of toxicosis were also included. Signalment, dose, clinical signs, treatment, and outcome were evaluated.
Results: Clinical signs of toxicosis were reported in 107 of 128 (84%) dogs that ingested MPH; these included hyperactivity in 42 (33%), tachycardia in 27 (21%), vomiting in 19 (15%), agitation in 16 (13%), and hyperthermia in 13 (10%). Doses ranged from 0.36 mg/kg (0.164 mg/lb) to 117.0 mg/kg (53.18 mg/lb). Severity of clinical signs was not strongly associated with dose. More severe and prolonged clinical signs were associated with ingestion of extended-release formulations of MPH; 3 dogs that consumed these formulations (doses, 10.2 mg/kg [4.64 mg/lb], 15.4 mg/kg [700 mg/lb], and 31.1 mg/kg [14.14 mg/lb]) died. Favorable outcomes were reported for most (31/34 [91%]) dogs.
Conclusions and clinical relevance: Ingestion of even small amounts of MPH can cause severe clinical signs in dogs. Monitoring and supportive care are recommended regardless of dose.