In this VETgirl online veterinary CE blog, we review amphetamine toxicity in dogs and cats. Amphetamines are used for a variety of medical and illicit reasons. Legal forms include prescription medications for attention-deficit disorder/attention deficit-hyperactivity disorder (ADD/ADHD), weight loss, and narcolepsy. Examples include dextroamphetamine and amphetamine (Adderall®), D-amphetamine (Dexedrine®), methamphetamine (Desoxyn®), and lisdexamfetamine (Vyvanse®)*. Illegal forms of amphetamines include street drugs like methamphetamine, crystal meth, and ecstasy. This class of drugs acts as sympathomimetic agents, meaning they stimulate the sympathetic system. Amphetamines also cause stimulation of α and β-adrenergic receptors, and stimulate release of serotonin and norepinephrine; this results in increased catecholamine stimulation in the synapse. Amphetamines also increase release of serotonin from the presynaptic membrane, resulting in serotonin syndrome.
*Note: With Vyvanse, clinical signs can be seen at 1 mg/kg in dogs; severe clinical signs (e.g., such as tremors, seizures, etc.) can be seen at 10 mg/kg.
With amphetamine toxicosis, secondary stimulation of certain body systems can result in significant clinical signs: CNS (e.g., agitation, mydriasis, tremors, seizures), cardiovascular (e.g., tachycardia, hypertension), GI (e.g., vomiting, diarrhea, hypersalivating), and respiratory (e.g., panting). Both clinical signs and treatment for amphetamine toxicosis are similar to SSRI toxicosis.
Treatment includes decontamination (ideally done at a veterinarian, due to the rapid onset of clinical signs), activated charcoal, hospitalization for sedation (e.g., with acepromazine or chlorpromazine), thermoregulation, intravenous (IV) fluid therapy, blood pressure and electrocardiogram (ECG) monitoring, muscle relaxants (for tremors; methocarbamol 22-55 mg/kg, IV), anticonvulsants (e.g., phenobarbital 4-16 mg/kg, IV), serotonin antagonists [e.g., cyproheptadine (1.1 mg/kg for dogs or 2-4 mg total per cat) PO or rectally q. TID-QID], and supportive and symptomatic care.
When in doubt, ASPCA Animal Poison Control Center should be consulted for life-saving advice as needed. Thankfully, with aggressive treatment, most veterinary patients respond well to treatment for amphetamines.