In patients who need to be initiation on dopaminergic agents, either levodopa or dopamine agonists can be used. Levodopa is better at improving motor functions, dopamine agonists are better at lessening motor complications. May also use a MAOI (rasagiline or selegiline only, they increase extracellular dopamine).
Carbidopa/Levodopa is the mainstay of therapy, but often clinicians will use a dopamine agonist as the first line in a younger patient to save carbidopa/levodopa, which has a limited effective life of 3-4 years.
- Wearing Off Phenomenon: the return of symptoms before the next dose. Add dopamine agonist, MAO-B, COMT inhibitor increase levodopa.
- On-Off Phenomenon: profound, predictable return of symptoms without respect to dosing interval. Add COMT inhibitor (entacapone) or rasagiline
- Dyskinesias are drug induced. Decrease levodopa or add amantadine.
- Bromocriptine 5-40 mg
- Pramipexole 1.5-4.5
- Ropinirole: 0.75-24
- Rotigotine: 6-8
- May cause nausea and vomiting, hypotension, hallucinating. hypersexuality and/or compulsive behavior. Monitor BP while titrating.
Anticholinergics: Trihexyphenidyl and benztropine are both 0.5-1 mg BID and cause dry mouth, urinary retention, dry eyes, constipation (think dry)
Amantadine: may reduce dyskinesia caused by levodopa, 100 mg BID to TID
COMT Inhibitors: Tolcapone is restricted due to hepatotoxicity. Entacapone must be used with levodopa/carbidopa, increases levodopa to the brain.