Anticholinergics (procyclidine, trihexyphenidyl)
This information explains the Parkinson's drugs anticholinergics including how they work, the benefits, and the different types.
How do anticholinergics work?
Anticholinergics block a chemical messenger called acetylcholine which is found in your brain and body. It helps to send messages in the brain, as well as from your nerves to your muscles.
In Parkinson’s the effect of acetylcholine is stronger. This can lead to part of the brain becoming overactive and you may have a tremor. Reducing the effect of acetylcholine can help to treat tremor.
When are anticholinergics used?
Anticholinergics are rarely used to treat Parkinson’s. They might help with some Parkinson’s symptoms but can make others worse. Anticholinergics are not a first choice for the treatment of Parkinson’s.
They can be used in younger people with a noticeable tremor. But older people who take anticholinergics are more likely to experience side effects such as confusion and hallucinations.
If you take them for a number of years, they can be quite difficult to stop and some people experience withdrawal symptoms.
Benefits of anticholinergics
Improving Parkinson’s symptoms
Some anticholinergics may help with tremor with some Parkinson’s symptoms when other medication is no longer working.
Anticholinergics may help with:
- rigidity
- slowness of movement
- tremor
- speech and writing difficulties
- gait (the way you walk)
- sweating
- involuntary (uncontrolled) movements of the eyes
- feeling depressed.
Improving sialorrhoea and drooling
Anticholinergics can help control saliva in your mouth, if you experience drooling or produce too much saliva (sialorrhoea).
UK guidelines suggest that you should be referred to a speech and language therapist before your specialist prescribes any medication for drooling, where possible. If this doesn’t happen, you could speak to your Parkinson’s nurse about a referral for speech and language therapy.
Injections of botulinum toxin (Botox) into the salivary glands may also help control problems with saliva. It’s important to discuss this with your specialist, as this treatment may have side effects, such as causing your mouth to be too dry. Clinical guidelines list Botox as a treatment option for people with Parkinson’s experiencing drooling, so it should be available for you on the NHS but may not be available in all areas.
Read our information on eating, swallowing and managing saliva in Parkinson’s.
Types of anticholinergics
Below are the types of anticholinergic drugs. Each drug has a generic (unbranded) name and a branded name.
Procyclidine
Procyclidine is available as unbranded tablets, oral solution and solution for injection. Kemadrin is the brand name for procyclidine. It's available as tablets.
Trihexyphenidyl
Trihexyphenidyl is available as unbranded tablets, oral solution and syrup.
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