A 65-year-old Caucasian male presents to your office with increasing muscle rigidity and gait instability. He was diagnosed with Parkinson disease two years ago and has been treated with selegiline. His past medical history is otherwise insignificant. His father suffered from Parkinson disease and his mother died of an extensive stroke. You consider switching to levodopa to control this patient's symptoms adequately and discuss the adverse effect profile of levodopa with him. Which of the following adverse effects is most likely to persist after adding carbidopa to levodopa treatment?

Question

A 65-year-old Caucasian male presents to your office with increasing muscle rigidity and gait instability.  He was diagnosed with Parkinson disease two years ago and has been treated with selegiline.  His past medical history is otherwise insignificant.  His father suffered from Parkinson disease and his mother died of an extensive stroke.  You consider switching to levodopa to control this patient's symptoms adequately and discuss the adverse effect profile of levodopa with him.  Which of the following adverse effects is most likely to persist after adding carbidopa to levodopa treatment?

Quizplus · Accepted Answer

Anxiety and agitation are central effects of dopamine and are caused by L-dopa, regardless of whether carbidopa is added to levodopa treatment. In fact, anxiety and agitation can be increased because more dopamine is available to the brain. (Adding carbidopa inhibits the peripheral conversion of levodopa, making more of it available to the brain.) High-dose combination levodopa/carbidopa can cause various behavioral changes such as anxiety, agitation, insomnia, confusion, delusions, and hallucinations. Reducing the dose is helpful in alleviating these adverse effects. If reduced dosage is not possible, atypical antipsychotics, such as clozapine, may be helpful. (Choice A) Nausea and vomiting are seen in up to 80% of patients when levodopa is used alone. Dopamine stimulates the emetic center located in the brainstem (which is outside of the blood brain barrier). Adding a dopa decarboxylase inhibitor reduces nausea and vomiting and significantly increases patient compliance. Most patients develop tolerance to nausea after several months. (Choice B) Tachyarrhythmias, such as ventricular extrasystoles and atrial fibrillation, are attributed to the increased peripheral formation of catecholamines. Adding a peripheral decarboxylase inhibitor reduces these arrhythmias. (Choices C and D) Postural hypotension and hot flashes also result from the peripheral conversion of levodopa to dopamine, so a peripheral decarboxylase inhibitor would decrease these problems. Educational Objective: Adding carbidopa can reduce most of the peripheral side effects of levodopa. However, behavioral changes from levodopa can actually worsen with addition of carbidopa because more dopamine becomes available to the brain.

A 65-Year-Old Caucasian Male Presents to Your Office with Increasing