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Anticholinergic Drugs

Anticholinergics Substances that block the neurotransmitter acetylcholine in the central and the peripheral nervous system; typically the main ingredient in over-the-counter sleep aids and many allergy medications (e.g., Benadryl). Trihexyphenidyl (formerly Artane), benztropine (Cogentin) and ethopropazine (Parsitan) are typical Parkinson’s medications in this class. can be helpful for tremor Involuntary shaking of the hands, arms, legs, jaw or tongue. The typical Parkinson’s tremor is “pill-rolling” – it looks like holding a pill between thumb and forefinger and continuously rolling it around. Some people report an internal tremor, a shaking sensation inside the chest, abdomen or limbs that cannot be seen. Most Parkinson’s tremor is “resting tremor,” which lessens during sleep and when the body part is actively in use. and may ease dystonia A disorder in which muscles contract uncontrollably, causing abnormal movements and postures; can be very painful. 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 chemical messenger (neurotransmitter) in the striatum area of the brain. It is involved in many brain functions, such as memory and control of motor activity. It is believed that acetylcholine and dopamine maintain a delicate balance in the brain. Lack of dopamine in people with Parkinson’s disrupts this balance. Anticholinergic medications block acetylcholine., a neurotransmitter A chemical messenger that carries impulses from one nerve cell to another. Dopamine, acetylcholine and norepinephrine are examples. that regulates movement. Potential adverse effects include blurred vision, dry mouth, constipation and urinary retention A lack of ability to urinate..

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®, 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.

Benzotropine Mesylate (Cogentin®)

Available Doses: 0.5 mg

Initial Dosing: 0.5 mg 2X/day

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

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

Interactions: Anti-histamines, Propulside®, Haldol®, Thorazine®, Clozaril®, alcohol

Trihexyphenidyl HCL (Artane®)

Available Doses: 1 mg, 2 mg

Initial Dosing: 1-2 mg 2X/day

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

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

Interactions: 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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