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Anticholinergic Drugs

Anticholinergics can be helpful for tremor and may ease dystonia associated with wearing-off or peak-dose effect. They have little effect on other symptoms of PD. The drugs in this class include trihexyphenidyl (Artane®), benztropine mesylate (Cogentin®) and procyclidine (no longer available in the U.S.), among others. They do not act directly on the dopaminergic system. Instead, they decrease the activity of acetylcholine, a neurotransmitter that regulates movement. Potential adverse effects include blurred vision, dry mouth, constipation and urinary retention.

Older individuals are susceptible to confusion and hallucinations on anticholinergics, so these agents should be avoided in people older than 70. 

Check with a doctor before using anticholinergics with anti-histamines, Haldol®, Thorazine®, Symmetrel®, Clozaril® and alcohol.

What are the facts?

  • Anticholinergics are the oldest class of medications to treat PD; they were first used in the 1900s.
  • Most helpful to younger patients with PD whose chief complaint is a tremor.
  • Ethopropazine, an anticholinergic and an antihistamine, may have fewer side effects, but is not available in most U.S. pharmacies.

What are the possible side effects?

  • Confusion
  • Hallucinations
  • Decreased short-term memory
  • Dry mouth
  • Blurry vision
  • Urinary retention

Caution: PD medications may have interactions with certain foods, other medications, vitamins, herbal supplements, over the counter cold pills and other remedies. Anyone taking a PD medication should talk to their doctor and pharmacist about potential drug interactions.

Medication

Available Doses

Initial Dosing

Side Effects*

Indications

Interactions

Benzotropine mesylate

(Cogentin®)

.5 mg

.5 mg 2X/day

Confusion, hallucinations, nausea, blurred vision, dry mouth, urinary retention, nervousness; not used long-term due to side effects

Secondary medication; tremor; attempts to restore balance by inhibiting other enzymes and nerve cells that may attack dopamine

Anti-histamines, Propulside®, Haldol®, Thorazine®, Symmetrel®, Clozaril®, alcohol

Trihexyphenidyl HCL

(Artane®)

1 mg

2 mg

1-2 mg 2X/day

Confusion, hallucinations, nausea, blurred vision, dry mouth, urinary retention, nervousness; not used long-term due to side effects

Secondary medication; tremor; attempts to restore balance by inhibiting other enzymes and nerve cells that may attack dopamine

Anti-histamines

* Please note that the side effects listed in the tables that accompany each class of medication are the most commonly experienced. Not all individuals will experience such side effects. For many people who do experience side effects, they can often be effectively limited or eliminated with careful adjustments to dosage or the timing of the individual doses.

Speak to the treating physician immediately if any side effects are experienced. For a complete description of each drug and its possible side effects, please request a “package insert” from your pharmacist for each drug used. It is recommended that all prescriptions be filled at the same pharmacy to avoid interactions between medications. Interactions can be dangerous and even life-threatening, so make sure the pharmacist knows of all medications and supplements being taken, including over-the-counter medications and supplements.

Page reviewed by Dr. Chauncey Spears, Movement Disorders Fellow at the University of Florida, a Parkinson’s Foundation Center of Excellence.

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