Parkinson’s disease is a common degenerative disease of the brain characterized by tremors, rigidity or stiffness of muscles, and difficulty with balance. It is caused due to the loss of dopamine secreting neurons in the part of the brain called substantia nigra. Many drugs are available to manage Parkinson’s disease, with carbidopa-levodopa being the cornerstone of therapy. Levodopa is converted to dopamine in the brain, while carbidopa prevents breakdown of levodopa so that enough levodopa can be delivered to the brain from the bloodstream.
Table showing drugs used to treat Parkinson’s disease and their mechanism of action
| Mechanism of action | Generic name and common brands | |
| Increase dopamine levels in the brain | Carbidopa-levodopa (Sinemet, Parcopa, Rytary, Dhivy) | |
| Dopamine agonists that mimic the action of dopamine | Apomorphine (Apokyn, Kynmobi), pramipexole (Mirapex), ropinirole (Requip), rotigotine (Neupro) | |
| MAO-B inhibitors that block the breakdown of dopamine | Rasagiline (Azilect), selegiline (Carbex, Eldepryl) | |
| COMT inhibitors that block the breakdown of dopamine | Entacapone (Comtan), tolcapone (Tasmar), opicapone (Ongentys) | |
| Anticholinergics that block the action of neurotransmitter acetylcholine | Benztropine (Cogentin), trihexyphenidyl (Artane) | |
| Adenosine receptor antagonist | Istradefylline (Nourianz) | |
| Increase dopamine levels in the brain | Fos Levodopa-fos carbidopa (Vyalev, Produodopa) | |
| Unknown mechanisms | Amantadine (Osmolex, Gocovri, Symmetrel) | |
Common adverse effects include nausea, vomiting, dizziness, headache, sleepiness, postural hypotension, confusion, hallucinations, delusions, agitation, and dry mouth. Urinary retention, dry mouth, and cognitive dysfunction are more common with anticholinergics.