A 60-year-old male patient with Parkinson's started on pramipexole; after a few weeks, he reports a side effect. What is the most likely adverse drug reaction?

• A. Binge eating
• B. Drowsiness
• C. Orthostatic hypotension
• D. Nausea

Answer: (A)

Dopamine agonists like pramipexole can trigger impulse control disorders, driving reward-seeking behaviors. The most telling ADR in this context is the emergence of binge eating, a compulsive behavior linked to overstimulation of mesolimbic reward pathways via dopamine receptors, particularly D3 receptors. This can appear after weeks of starting therapy as patients experience strong, uncontrollable urges to eat. While common side effects such as drowsiness, nausea, and orthostatic hypotension may occur early, they don’t reflect a behavioral change driven by reward circuitry. If binge eating develops, the approach is to reduce or discontinue the dopaminergic agent and explore alternative Parkinson’s treatments, with careful follow-up to ensure the behavior resolves and to support the patient and family.