Which of the following represents the mode of action of ropinirole?


#1

A 73-year-old man with a history of Parkinson’s disease is brought to the clinic by his family. They are concerned about a change in his behaviour over the past few months associated with starting ropimrole for the treatment of Parkinson’s disease. He has been sleeping excessively in the day, and has also taken to gambling large amounts of money on a poker machine at the local bookmakers.
Which of the following represents the mode of action of ropinirole?

A Anti<holinergic
B COMT inhibitor
Dopamine agonist
D G lutamate antagonist
E MAO·B inhibitor

Ropimrole is a dopamine agonist used in the treatment of Parkinson’s disease, specifically it is a 02103 agonist, (nonergot), hence it does not carry the liability of pulmonary or cardiac fibrosis of earlier compounds used for the indication. It is associated with an increase in risk taking behaviour, and changes in sleep patterns.

Anti-cholinergic, (Option A), is incorrect. Anti<holinergics are used primarily to improve tremor, examples include orphenadrine and procyclidrne.
COMT inhibitor, (Option B), is incorrect. COMT inhibitors block metabolism of levodopa, and tend to be used late in the treatment of the condition. Examples include entacapone.
Glutamate antagonist, (Option D). is incorrect. Amantadine is a glutamate antagonist, it has relatively weak effects in terms of improving tremor and rigidity, as such it is rarely used in the treatment of Parkinson’s.
MAO·B inhibitor. (Option E), is incorrect. Monoamine oxidase is responsible for dopamine metabolism, as such inhibiting it potenltates the action of dopamine and L·dopa, improving Parkinson’s symptoms. Selegiline is an example of the class.