Which medication is often prescribed for patients who are unable to tolerate carbidopa-levodopa?

Bromocriptine mesylate is often prescribed for patients who are unable to tolerate carbidopa-levodopa because it is a dopamine agonist that mimics the action of dopamine in the brain. This can be particularly beneficial for patients with Parkinson's disease who do not respond well to, or experience side effects from, carbidopa-levodopa therapy. Bromocriptine can help control motor symptoms by directly stimulating dopamine receptors, thereby providing another viable option for managing the disease while minimizing the complications associated with levodopa therapy.

In contrast, while other medications listed have roles in treating Parkinson's disease or related symptoms, they are not typically the primary alternatives for those specifically intolerant to carbidopa-levodopa. Pramipexole is also a dopamine agonist, and while it could be used in this context, bromocriptine is the more classic choice historically. Apomorphine is often reserved for advanced stages of Parkinson's or for treatment of 'off' episodes and selegiline acts as an MAO-B inhibitor and may not be the best substitute for patients who cannot tolerate the more potent dopaminergic effects of carbidopa-levodopa.