Adverse effects

  1. Home
  2.  | 
  3. Working with Voices
  4.  | 
  5. Medication
  6.  | Adverse effects

“Twisty arms and legs. Agitation – deep in your bones. I had to keep bouncing up. Couldn’t relax. You can’t sit still. Have to keep moving.”


“Everything is muted. Bleeding the joy out of life. The meds greatly reduce my physical ability. [There are] days where I just feel wiped out.”


“Twisty arms and legs. Agitation – deep in your bones. I had to keep bouncing up. Couldn’t relax. You can’t sit still. Have to keep moving.”


“Everything is muted. Bleeding the joy out of life. The meds greatly reduce my physical ability. [There are] days where I just feel wiped out.”


The adverse effectsquestion icon which may be experienced by any person on any particular antipsychotic drug are difficult to predict. Some drugs are known to be more likely to have a particular effect than others, and some people may be completely unaffected. Similarly, just because a drug is not known to cause a particular effect, it doesn’t mean it won’t in some people.

Here we provide an alphabetical list of some of the adverse effects reported by people taking antipsychotic medication. Remember, some of these are very rare so the majority of people taking the medications in question won’t experience them.

Important note: If you are worried about any of these adverse effects, please talk to a healthcare provider or mental health pharmacist. Stopping medication suddenly can trigger ‘rebound psychosisquestion icon’ and distressing withdrawal effectsquestion icon. If you are concerned your healthcare provider will not listen to you, or you’ll struggle to get your voice heard, speak to an advocate.


Akathisia is a feeling of intense restlessness that is often linked with involuntary movements (pacing, rocking from foot to foot, shifting weight whilst sitting) and a need to keep moving. In severe cases people may feel extremely distressed, have problems sleeping and feel overwhelmed with difficult thoughts and impulses. Akathisia can be acute (develops on starting a drug), tardive (develops months after starting the drug), withdrawal (happens when stopping a drug) or chronic (any type that lasts more than 6 months).

Blood disorders

Antipsychotics are linked to a range of blood disorders, including ‘neutropenia’ – a low concentration of neutrophils (a type of white blood cell) in the blood. Often this change is temporary. In severe cases, this is called ‘agranulocytosis’ and makes people more likely to catch infections and less able to fight them. Symptoms of agranulocytosis are similar to having a bacterial infection, including a sudden fever and weakness.

The risk of developing neutropenia is low, and mainly linked to Clozapinequestion icontreatment, which is offered in the UK to people who have tried two different antipsychotic medications and found them ineffective. Roughly 3% of people taking Clozapine develop neutropenia, with about 1% developing the more severe agranulocytosis. Other antipsychotics are considered much less of a risk.

People taking Clozapine are required to have regular blood tests as part of a national management system that picks up early signs of neutropenia.

Cognitive impairment

Some people report difficulties with concentration, memory and learning while taking antipsychotic medication. On the other hand, some research studies show that antipsychotics can improve cognition.

Drooling (Hypersalivation)

The overproduction of saliva can lead to drooling during the night and, in extreme cases, increase the risk of aspiration pneumonia. If drooling becomes a problem, people may be prescribed medications to help them manage the condition – for example, scopolamine, pirenzepine and atropine.

Dry mouth

Whilst it can happen to anyone, especially when they feel stressed, a persistent dry mouth is associated with the use of antipsychotic drugs and can cause a range of problems. Lack of saliva can cause difficulties with chewing, swallowing and talking. It can also increase the risk of tooth decay and fungal infections because saliva helps keep the mouth clean. Some people find regular sips of water, sucking on ice cubes and sucking on sugar free (e.g. diabetic) sweets helps to counteract this side effect. The increased risk of tooth decay makes dental care very important while taking antipsychotic medication.

Eye problems

Antipsychotics have been linked to different eye problems, including blurred vision, glaucomaquestion icon, degeneration of the retina (the light sensitive part of the eye) and ‘oculogyric crisis’ – involuntary upward turning of the eyes. People with a history of glaucoma should be particularly cautious about taking antipsychotic drugs.

Extra Pyramidal Side Effects

These effects resemble Parkinson’s diseasequestion icon, and may include muscle weakness, losing animation in your face, finding fine movements difficult, a slow tremor (shaking), difficulties walking, and dribbling.

Gastrointestinal problems

Neuroleptic medication can affect people’s digestive system in different ways, including constipation diarrhoea, nausea and vomiting. Clozapine, for example, is linked to slower transit through the bowels which causes constipation. If constipation is not addressed there is an increased risk of blockages and complications.

It’s important that people who take Clozapine mention issues with constipation to their healthcare professional because of the increased risk of complications. See the following resources for more information:

Constipation, NHS Choices

Feeling sick, NHS Choices

The IBS Network self-care programme

Heart problems

Increased heart rate, palpitations, arrhythmiaquestion iconand Long QT syndromequestion icon (in which the heart muscle takes longer than normal to recharge between beats) are often associated with antipsychotic drugs. They can also increase the risk of cardiovascular disease and heart attack.

Liver problems

Antipsychotics may cause liver problems, signs of which include jaundicequestion icon (yellow skin), swelling the stomach, legs and ankles, itching, dark urine, chronic tiredness and nausea. Regular monitoring, in line with NICE guidelines, is important – especially at the beginning of antipsychotic treatment. Reducing other lifestyle factors which can harm the liver can also help, including sensible use of alcohol, eating healthily and avoiding hepatitis.

Metabolic syndrome

Metabolic syndrome is diagnosed when someone has three or more of: increased weight circumference, high blood pressure, low high-density lipoprotein cholesterolquestion icon, hypertriglyceridemiaquestion iconand high blood sugar (diabetesquestion icon). It can result from a combination of increased appetite/food intake, sedation (leading to a sedentary lifestylequestion icon) and direct drug effects (independent of lifestyle factors).

Neuroleptic Malignant Syndrome (NMS)

Although NMS is rare, awareness and early identification (amongst people taking antipsychotics, their supporters and medical professionals) is of crucial importance. If NMS is suspected, the NHS recommends seeking urgent medical care, telling practitioners the medications that are being taken and that there is a risk of this condition.


Sedation is a commonly reported in people taking antipsychotic medication, who often describe feeling sleepy or ‘knocked out’. If excessive, sedation can make it difficult to engage in everyday life. Taking medication in the evening or just before bed is useful when medications have a sedative effect.


Seizuresquestion icon affect different people in different ways. They can include changes in awareness, periods of forgetfulness, feeling detached, tingling, difficulty speaking, loss of movement, rigidity, repeated movements and convulsions.

Sexual and reproductive difficulties

Antipsychotics can cause loss of libido (sexual desire), difficulties getting or sustaining an erection, retrograde ejaculation (where semen is redirected to the bladder rather than out through the urethra), priapism (long-lasting, and often painful, erection) and inability to orgasm.

29–49% of women and 45–59% of men experience at least some symptoms of sexual dysfunction whilst taking antipsychotics. For women, the most common issues seem to be lack of menstruation/periods (39%) and low sexual interest (26%). For men, the most common issues seem to be low sexual interest (37%) and erectile dysfunction and ejaculation problems. Being prescribed more than one second-generation antipsychotic at the same time may increase risk, as can taking higher doses of certain drugs.

Reducing the dose or switching to a medication that is less likely to cause these difficulties can help to deal with these effects.

Tardive Dyskinesia

Tardive Dyskinesia is an umbrella term for involuntary repetitive movements – often involving the face and tongue – that start when someone has been taking antipsychotic medication for many months. It can include lip smacking and chewing or slow and writhing movements. Severe tardive dyskinesia can affect swallowing and speech.

There is no clear evidence on an effective treatment for Tardive Dyskinesia as the quality of research is low. However, approaches include dose reduction, switching to another medication and adding extra treatments (including benzodiazepinesquestion icon, buspironequestion icon, ginkgo bilobaquestion icon, relaxation and hypnosisquestion icon).

You can find out more about Tardive Dyskinesia by following these links:

Understanding tardive dyskinesia, Mind.
How to cope with tardive dyskinesia, The Mighty.

Tardive psychosis

‘Tardive psychosis’ is medical term used to describe a new set of unusual and disturbing experiences, including visions and voices, which arise after you have been taking antipsychotics for a period of time and which are directly caused by your medication.

Weight gain

Weight gain is usually worse at the beginning of treatment and is most often noticed when someone first starts medication. Although the reasons why people gain weight when taking antipsychotics are not very well understood, it is often linked to increased appetite and the effects of sedation. Taking regular exercise and a healthy diet can help to control this.

Find out more

For more detailed and independent information on adverse effects, see:

Risk: Making medications safer for us all

A drug safety website that can help you weigh the benefits of any medication against its potential dangers

Antipsychotics – what side effects can they cause?, Mind.

Accessible information about the adverse effects of different antipsychotic drugs

Comparing antipsychotics, Mind.

A full list of all antipsychotics licensed for use in the UK, with information about half-life, whether they are suitable for people with specific dietary requirements, and links to patient information leaflets for each drug.

If you would like report the adverse effects of your medication, please see the reporting site for the Yellow Card scheme, which helps monitor the safety of all healthcare products in the UK.

Share This