4.9.2 Antimuscarinic drugs used in parkinsonism
|1st choices||Procyclidine tablets 5mg|
|Trihexyphenidyl hydrochloride tablets 2mg, 5mg|
Dose: 1mg daily, increased by 2mg every 3-5 days according to response; usual maintenance dose 5-15mg daily in 3-4 divided doses (max 20mg daily); elderly preferably lower end of range – see cautions
- Antimuscarinics are sometimes used as a first line therapy in young onset Parkinson’s Disease under specialist supervision, but not generally recommended in older patients – see Cautions
- Antimuscarinics may occasionally be useful in patients with tremor which is unresponsive to other drugs, on the advice of a specialist.
- Tardive dyskinesia is not improved by antimuscarinic drugs and may be made worse.
- Antimuscarinics may cause cognitive impairment and urinary retention. They should be avoided in older patients.
- Antimuscarinics are not generally recommended for use in Parkinson’s Disease because of toxicity in the elderly and the risk of aggravating dementia.
- Abrupt withdrawal of antimuscarinics should be avoided.