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Antipsychotics: Types of antipsychotics 

From: Understanding psychiatric medications: Antipsychotics - Information for consumers, families and friends (© 2009, 2012 CAMH)

Antipsychotic medications are generally divided into two categories: first generation (typical) and second generation (atypical). The main difference between the two types of antipsychotics is that the first generation drugs block dopamine and the second generation drugs block dopamine and also affect serotonin levels. Evidence suggests that some of the second generation drugs have milder movement- related side-effects than the first generation drugs.

Both categories of drugs work equally well overall, although no drug or type of drug works equally well for everyone who takes it. When the same drug is given to a group of people, one third of that group will find that it works well; another third will find that the drug helps only with some symptoms; and the final third will find that it does not help at all. For this reason, people may need to try different antipsychotics before finding the one that works best for them.

Most of these drugs are given in tablet form, some are liquids and others are given as injections. Some are available as long-lasting (depot) injections, which may be given anywhere from once a week to once a month.

Antipsychotics are often used in combination with other medications to treat other symptoms of mental health problems or to offset side-effects.

Most people who take antipsychotics over a longer term are now prescribed the second generation (also called atypical) drugs.

Second generation (atypical) antipsychotics

Medications available in this class include risperidone (Risperdal)*, quetiapine (Seroquel), olanzapine (Zyprexa), ziprasidone (Zeldox), paliperidone (Invega), aripiprazole (abilify) and clozapine (clozaril). clozapine is exceptional in that it often works even when other medications have failed; however, because it requires monitoring of white blood cell counts, it is not the first choice for treatment.

The second generation antipsychotics are usually the first choice for the treatment of schizophrenia. although they may not be officially approved for these other uses, they are sometimes used in the treatment of mood and anxiety disorders, such as bipolar, posttraumatic stress and obsessive-compulsive disorders.

Some possible side-effects of this type of medication include dry mouth, dizziness, blurred vision and, rarely, seizures. The following table lists other side-effects of second generation antipsychotics and shows which drugs are most likely to least likely to have these effects.

*medications are referred to in two ways: by their generic name and
by their brand or trade names. Brand names available in canada appear here in brackets.

Side-effects of second generation antipsychotics
Drugs most likely
to least likely to have these effects
Weight gain, diabetes  clozapine > olanzapine > quetiapine > risperidone > ziprasidone, aripiprazole
movement effects (e.g., tremor, stiffness, agitation)
risperidone > olanzapine, quetiapine, ziprasidone, aripiprazole > clozapine
Sedation (e.g., sleepiness, low energy)
clozapine, olanzapine and quetiapine > risperidone, ziprasidone, aripiprazole
Decreased sex drive and function, missed periods, discharge from breasts
risperidone > olanzapine, quetiapine > clozapine, ziprasidone

First generation (typical) antipsychotics

These older medications include chlorpromazine (once marketed as Largactil), flupenthixol (Fluanxol), fluphenazine (Modecate), haloperidol (Haldol), loxapine (Loxapac), perphenazine (Trilafon), pimozide (Orap), trifluoperazine (Stelazine), thiothixene (Navane) and zuclopenthixol (Clopixol).

Side-effects of this group of medications vary depending on the drug and may include drowsiness, agitation, dry mouth, constipation, blurred vision, emotional blunting, dizziness, stuffy nose, weight gain, breast tenderness, liquid discharge from breasts, missed periods, muscle stiffness or spasms.


Side-effects of antipsychotics

Movement effects

Tremors, muscle stiffness and tics can occur. The higher the dose, the more severe these effects. The risk of these effects may be lower with the second generation medications than with the older drugs. Other drugs (e.g., benztropine [Cogentin]) can be used to control the movement effects.


Feelings of dizziness may occur, especially when getting up from a sitting or lying position.

Weight gain

Some of the second generation drugs are thought to affect people’s sense of having had enough to eat. They can also be sedating. These two effects can result in weight gain, which can increase a person’s risk of diabetes and heart disease.


Schizophrenia is a risk factor for diabetes. Antipsychotic drugs can increase this risk.

Agitation and sedation

Some people feel “wired” and unable to stop moving when taking antipsychotics. This effect may be mistaken for a worsening of illness rather than a side-effect of the medication. These same drugs can also have the opposite effect, making people feel tired. Some people may feel either wired or tired, and some may feel both at the same time.

Tardive dyskinesia

For every year that a person takes anti- psychotic medication, there is a five per cent chance of developing tardive dyskinesia (TD), a condition that causes people to have repetitive involuntary movements. The risk
of TD is highest with the first generation antipsychotics, although it can occur with the second generation drugs. TD can worsen when you stop taking medication and can be permanent.

Neuroleptic malignant syndrome

This rare but serious complication is usually associated with the use of high doses of typical antipsychotics early in treatment. Signs include fever, muscle stiffness and delirium.

Controlling side-effects

You can help to control possible side-effects on your own by:

  • getting regular exercise and eating a low- fat, low-sugar, high-fibre diet (e.g., bran, fruits and vegetables) to reduce the risk of diabetes and help prevent weight gain and constipation
  • using sugarless candy or gum, drinking water and brushing your teeth regularly to increase salivation and ease dry mouth
  • getting up slowly from a sitting or lying position to help prevent dizziness.

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