Mental health: Managing side effects (part 1)

Last updated: Monday, April 29, 2024

You may be asked for advice on how to manage side effects in patients taking psychiatric medicines. Compared to other therapeutic areas, the medicines used in mental health are particularly likely to be linked to groups of related adverse effects or syndromes, rather than individual complaints.

Extrapyramidal side effects

For example, certain antipsychotics can cause well-established patterns of extrapyramidal side effects. These are characterised by movement disorders such as:

  • Acute dystonia (involuntary muscle contraction) 
  • Akathisia (increased restlessness often in lower limbs, feeling of ‘unease’ and irritability)
  • Parkinsonism (bradykinesia, tremor, rigidity)
  • Tardive dyskinesia (involuntary movement including myoclonic jerks, tics, chorea and dystonia)

If some of these terms are unfamiliar to you, there are US videos describing acute dystonia, akathisia, and tardive dyskinesia that may help you. They describe the presentation of these conditions, but the treatments and terminology sometimes represent US rather than UK practice.

Anticholinergic burden

Acetylcholine is a neurotransmitter that mediates activities such as peristalsis, bladder emptying, slowing of the heart, saliva production, control of body temperature, and focusing of the eye. It is also found in the brain where, amongst other actions, acetylcholine helps alertness, concentration, and learning. Given the widespread role of acetylcholine in controlling basic body functions, medicines with anticholinergic properties can cause a broad range of side effects. Many medicines have anticholinergic side effects, also known as antimuscarinic effects, which are additive when more than one of these types of drug is taken together. Mental health medicines such as tricyclic antidepressants, many antipsychotics, and procyclidine can all cause these symptoms, as well as medicines used for non-mental health reasons such as hyoscine, oxybutynin, carbamazepine, and older antihistamines like chlorphenamine.


As you can see, anticholinergic side effects are numerous and quite diverse, and they may present in ways which make a drug-related cause not immediately obvious. The dizziness and sedation due to these medicines may cause falls in the elderly, for example, and dry mouth may contribute to dental decay. Importantly, anticholinergic medicines may also contribute to the development of cognitive impairment and symptoms easily mistaken for onset of dementia in older patients. For these reasons, anticholinergic medicines must be used with care in this population and avoided when possible. 

Two UK websites allow you to calculate an anticholinergic burden score for individual patients by estimating the ability of all their medicines to block the actions of acetylcholine. Take a look at one or both of these now: ACB Calculator and Medichec.  

We have also written a short, separate tutorial on managing the side effects of anticholinergic medicines. It's intended for clinicians in a primary care setting, but it's a good way to refresh your knowledge of this important topic.