A 57-year-old man comes to the office accompanied by his wife for follow-up of Parkinson disease. The patient reports no change in motor symptoms, and the disease has been well controlled with anti-Parkinson medication. However, his wife is very concerned about a change in behavior, reporting that he recently started gambling and has lost a significant amount of their savings. The patient drives several hours multiple times a week to gamble at a casino in a neighboring state. His only other medical condition is major depressive disorder for which he takes sertraline. The patient does not use tobacco, alcohol, or illicit drugs. Vital signs are within normal limits. Physical examination shows a mild resting hand tremor and minimal rigidity. Which of the following is most likely responsible for this patient's recent change in behavior?

Question

A 57-year-old man comes to the office accompanied by his wife for follow-up of Parkinson disease.  The patient reports no change in motor symptoms, and the disease has been well controlled with anti-Parkinson medication.  However, his wife is very concerned about a change in behavior, reporting that he recently started gambling and has lost a significant amount of their savings.  The patient drives several hours multiple times a week to gamble at a casino in a neighboring state.  His only other medical condition is major depressive disorder for which he takes sertraline.  The patient does not use tobacco, alcohol, or illicit drugs.  Vital signs are within normal limits.  Physical examination shows a mild resting hand tremor and minimal rigidity.  Which of the following is most likely responsible for this patient's recent change in behavior?

Quizplus · Accepted Answer

Parkinson disease (PD) is caused by loss of dopaminergic neurons in the basal ganglia, resulting in symptoms of bradykinesia, tremor, and rigidity. Dopaminergic medications used to treat PD have been associated with the abrupt onset of impulse control disorders, including pathological gambling, compulsive buying, and compulsive sexual behavior. Dopamine agonists (eg, pramipexole) as a class are most frequently associated with this adverse effect. These drugs act by binding to central dopamine receptors and stimulating dopamine activity in the ventral striatum (includes the nucleus accumbens, which is involved in motivation and reward pathways) and substantia nigra. Patients on dopamine agonist therapy should be monitored for dysfunctional impulse control. Gradual taper of the offending agent results in improvement in most cases. (Choice A) Decreased peripheral conversion of levodopa is the mechanism of action of carbidopa, a drug used in combination with levodopa (a dopamine precursor) to increase the availability of levodopa in the central nervous system. Compared to dopamine agonists, carbidopa-levodopa is much less likely to precipitate impulse control disorders. (Choice B) Increasing norepinephrine levels in the synaptic cleft is the mechanism of action of atomoxetine, a nonstimulant medication used in the treatment of attention deficit hyperactivity disorder. (Choice C) Increasing serotonin levels in the synaptic cleft is the mechanism of action of selective serotonin reuptake inhibitors (eg, sertraline). These medications are not associated with the onset of impulse control disorders and have actually been shown to decrease impulsivity. (Choice E) Upregulation of brain nicotinic acetylcholine receptors is a neuroadaptive response to the receptor desensitization that occurs with chronic repeated exposure to high levels of nicotine. Educational objective: Dopamine agonist medications used to treat Parkinson disease have been associated with the abrupt onset of impulse control disorders, including pathological gambling, compulsive buying, and compulsive sexual behavior. The behavior is thought to be mediated by stimulation of central dopamine receptors. __________ References: Dopamine agonists and impulse control disorders: a complex association. (http://www.ncbi.nlm.nih.gov/pubmed/28861870)

A 57-Year-Old Man Comes to the Office Accompanied by His