This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
Which of the following dopamine agonists used in treatment of parkinsonism is available as a transdermal patch but not oral formulation? 
Select and explain. 
A. Apomorphine, B. Ropinirole, C. Rotigotine, D. Pramipexole
C: Rotigotine
Answer: C: Rotigotine 
Explanation: Both ropinirole and pramipexole are available as orally administered immediate (tid) and extended-release (qd) formulations. Rotigotine is administered as a once-daily transdermal patch, and may be useful in managing surgical patients who are NPO. Apomorphine is a dopamine agonist with efficacy comparable to levodopa, but it must be administered parenterally as it is rapidly and extensively metabolized if taken orally. Ref harrison 20th edition page 3127