PARK Module 6 Infographic

Dual Mechanism

How Amantadine Works

N-methyl-D-aspartate receptor antagonist — reduces glutamate-driven dyskinesias
Enhances dopamine release from presynaptic terminals
Only drug with established efficacy for levodopa-induced dyskinesias
Also used as mild monotherapy in early disease

Adverse Effects

Amantadine Adverse Effects

Livedo reticularis — mottled purplish skin discoloration (distinctive, benign)
Peripheral edema — especially ankles
Confusion, hallucinations — dose-dependent, worse in elderly
Renally excreted unchanged — dose reduce in renal impairment

Oral — Longer Duration

Benztropine

Mechanism

Muscarinic receptor antagonist — reduces striatal cholinergic excess

Best for

Tremor and rigidity — not bradykinesia

Also used

Acute drug-induced dystonia (injectable form)

Patients

Younger, tremor-predominant disease only

Oral — Chronic Use

Trihexyphenidyl

Mechanism

Muscarinic receptor antagonist — same class as benztropine

Best for

Tremor — limited benefit for bradykinesia

Adverse effects

Dry mouth, urinary retention, constipation, blurred vision, confusion

Patients

Younger patients — avoid in elderly

Beers Criteria

Anticholinergic drugs for Parkinson's disease are listed on the Beers Criteria as potentially inappropriate in adults over 65. Central muscarinic blockade impairs memory and can precipitate delirium. Use levodopa-carbidopa in elderly patients — reserve anticholinergics for younger patients with tremor-predominant disease.