Theoretically, it works by increasing dopamine levels, which downregulates the release of ACTH, eventually leading to reduced levels of cortisol. Some claim that selegiline is only effective at treating PDH caused by lesions in the anterior pituitary (which comprise most canine cases). The greatest sign of improvement is lessening of abdominal distention. Side effects in dogs are uncommon, but they include vomiting, diarrhea, diminished hearing, salivation, decreased weight and behavioral changes such as hyperactivity, listlessness, disorientation, and repetitive motions. Selegiline does not appear to have a clinical effect on horses. Research Selegiline has been limitedly studied in the treatment of attention deficit hyperactivity disorder (ADHD) in both children/adolescents and adults. In a small randomized trial of selegiline for treatment of ADHD in children, there were improvements in attention, hyperactivity, and learning/memory performance but not in impulsivity. In another small randomized controlled trial of selegiline for the treatment of adult ADHD, a high dose of the medication for 6 weeks was not significantly more effective than placebo in improving symptoms. References Propargyl compounds Antiparkinsonian agents Dopamine reuptake inhibitors Enantiopure drugs Euphoriants Monoamine oxidase inhibitors Neuroprotective agents Nootropics Phenethylamines Prodrugs Sigma receptor ligands Stimulants Substituted amphetamines Attention deficit hyperactivity disorder management World Anti-Doping Agency prohibited substances