Parkinson's disease
Parkinson’s disease is a common degenerative disorder of the brain. It’s characterized by:
- Tremor
- Rigidity (muscle stiffness)
- Difficulty with balance
Parkinson’s disease is caused by the loss of dopamine-secreting neurons in a part of the brain called the substantia nigra.
Many drugs are used to manage Parkinson’s disease, and carbidopa-levodopa is the cornerstone of therapy.
- Levodopa is converted to dopamine in the brain.
- Carbidopa reduces the breakdown of levodopa before it reaches the brain, so more levodopa can be delivered from the bloodstream into the brain.
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 and vomiting
- Dizziness and headache
- Sleepiness
- Postural hypotension
- Confusion
- Hallucinations and delusions
- Agitation
- Dry mouth
Anticholinergics are more likely to cause:
- Urinary retention
- Dry mouth
- Cognitive dysfunction