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Explains what antipsychotics are used for, how the medication works, possible side effects and information about withdrawal.
Anti-Parkinson's drugs are intended primarily for treating Parkinson's disease. They are not psychiatric drugs, which means they are not licenced to treat any mental health problems. However they may be prescribed alongside an antipsychotic to reduce neuromuscular side effects which resemble symptoms of Parkinson’s disease.
The three anti-Parkinson's drugs which may be prescribed with antipsychotics are:
Anti-Parkinson's drugs are sometimes referred to as 'antimuscarinics' because their main side effects are antimuscarinic. There are no significant differences between these drugs, but you may find that you tolerate one better than another.
You should only be prescribed an anti-Parkinson's drug if you have actually developed Parkinsonism as a side effect of your antipsychotic and:
These drugs should never be prescribed to prevent side effects from occurring if you haven't already experienced any.
You should be particularly cautious about taking these drugs if you have:
You should try to avoid these drugs if you:
Unfortunately, because this drug was first licensed before the current system of recording side effects was widely used, estimates of how likely you are to experience different side effects are not available for trihexyphenidyl. All side effects are listed here in alphabetical order, but you might find them listed in order of how common they are in the patient information leaflet (PIL) – the leaflet that comes in the drug packet.
This information was published in 2016. We will revise it in 2019.
References are available on request. If you would like to reproduce any of this information, see our page on permissions and licensing.