A 63-year-old woman returns with a 4-year history of advanced Parkinson's disease. Currently, her medication is only effective for 4 hours, after which her tremors become more severe, handwriting "cramped", and walking is worse. She denies involuntary movements with her medication (dyskinesias), falls, or "freezing" of gait. Her neuropsychiatric review demonstrates no history of depressed mood, anxiety, hallucinations, or significant cognitive impairment. She continues to work part-time, is driving, and has no sleep impairment or daytime somnolence from her medication. Presently she is taking levodopa-carbidopa 25/100 mg po tid.

1. Explain the mechanism of actions and adverse effects of levodopa-carbidopa. (USLO 4.3, 4.4)
2. Why is 'carbidopa' a critical part of levodopa-carbidopa? Include the term 'peripheral' in your answer and explain it. (USLO 4.1, 4.2, 4.4)
3. For a patient diagnosed with Parkinson's disease, what other prototype medication from this week may be used? How is it different/similar to levodopa-carbidopa? (USLO 4.1, 4.2, 4.4)