Antipsychotic Medications

Antipsychotics were discovered in the late 1950s.  This first antipsychotic drug, chlorpromazine, was first developed as a “tranquilizer.” Its usefulness for treating psychosis was recognized by accident. It was found to decrease positive symptoms such as hallucinations, delusions, and thought disorder.

Over the years several other similar drugs were developed and many continue to be used today. This class of drugs is referred to as Typical Antipsychotics or First Generation Antipsychotics.

Over the last 20 years, a new class of drugs has been developed known as Atypical Antipsychotics or Second Generation Antipsychotics.  These medications produce different side effects than the typical antipsychotics and are generally tolerated better by most people who take them.

Both Typical and Atypical classes of drugs are equally effective at treating positive symptoms. Around 2/3 of people experience a reduction in symptoms with the first medication they are prescribed within a matter of days or weeks. Side effects differ from drug to drug and from person to person.  Many people experience minimal or no side effects.

Most guidelines for treatment recommend starting with an atypical antipsychotic.   In order to reduce the potential of side effects, treatment should begin with a low dose, gradually increasing until an effective dose is established that treats the symptoms but remains well tolerated by the individual. Emergency and urgent situations may require the need to increase medication more quickly.

Examples of antipsychotic drugs

Typical Antipsychotics

  • Chlorpromazine
  • Flupenthixol
  • Haloperidol
  • Loxapine
  • Trifluperazine
  • Zuclupenthixol

Atypical Antipsychotics

  • Clozapine (Clozaril)
  • Olanzapine (Zyprexa)
  • Risperidone (Risperdal)
  • Quetiapine (Seroquel)
  • Paliperidone (Invega)
  • Ziprasidone (Zeldox)
  • Aripiprazole (Abilify)


Finding the right medication can sometimes be like finding the right new shoes: trial and error can sometimes be necessary since shoe size doesn’t always dictate comfortable fit.

This may be the most effective of all the antipsychotics in the treatment of psychosis.

However, this medication is not suitable for everyone.

Five percent of individuals get a temporary decrease in their white blood cell count, which could lead to serious infections. In order to prevent any problems, users must have weekly blood testing (every two weeks after 6 months) and discontinue the drug immediately should there be a drop in the white cell count. Other side effects include weight gain, sedation, constipation and increased saliva.

This medicine has been proven to be more effective for some of the 20% or so of people who have not responded to other medicine.  Because of the potential side effects and the need to closely monitor with blood tests, clozapine is reserved in Canada for use after a person has not responded to at least two other antipsychotic medications.