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Study on Continuing or Reducing Antipsychotic Medication (Haloperidol, Clozapine, Tiapride) for Patients After First Episode of Psychosis

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The HAMLETT study focuses on patients who have experienced a first episode of psychosis and are currently in remission, meaning their symptoms have improved or disappeared. The study examines the effects of continuing versus reducing or stopping the use of antipsychotic medication after this initial recovery. The medications being studied include Haloperidol, Clozapine, Tiapride, Sertindole, Paliperidone, Olanzapine, Sulpiride, Aripiprazole, Lurasidone, Risperidone, Amisulpride, Chlorpromazine, Pimozide, and Quetiapine. The purpose of the study is to understand how these different approaches affect personal and social functioning over both the short term (1-2 years) and long term (3-4 years).

Participants in the study will be randomly assigned to either continue their current antipsychotic medication or to gradually reduce or stop it. The study will monitor various aspects of their health and well-being, including any side effects from the medication, overall quality of life, and any changes in their physical and mental health. The study will also look at how these changes affect their ability to function in daily life, including their social interactions and personal well-being.

The study will take place over several years, with regular check-ins to assess the participants' progress. The primary focus is on long-term social recovery, which is considered important by both patients and their families. Additional factors being monitored include the severity of any remaining symptoms, physical health indicators like body mass index, and any instances of aggression or self-harm. The study aims to provide valuable insights into the best treatment strategies for individuals recovering from a first episode of psychosis.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Participation begins after experiencing a first episode of psychosis and achieving remission for 3-6 months.

    Eligibility includes being between 16-60 years old, understanding the study, and providing written consent.

  2. Step 2

    Initial assessment

    An initial assessment evaluates personal and social functioning using the World Health Organization's Disability Assessment Schedule (WHODAS-II).

    Additional evaluations include personal wellbeing, quality of life, symptom severity, and physical health.

  3. Step 3

    Medication management

    The study compares continuation of antipsychotic medication with dose reduction or discontinuation.

    Medications involved may include haloperidol, clozapine, tiapride, sertindole, paliperidone, olanzapine, sulpiride, aripiprazole, lurasidone, risperidone, amisulpride, chlorpromazine, pimozide, and quetiapine.

  4. Step 4

    Ongoing monitoring

    Regular monitoring of side effects, cognitive functioning, and movement disorders is conducted.

    Social functioning and well-being are assessed using ecological momentary assessments (EMA).

  5. Step 5

    Evaluation of outcomes

    Primary outcomes focus on long-term social recovery.

    Secondary outcomes include physical health, aggression, self-harm, and substance use.

  6. Step 6

    Study duration

    The study examines both short-term effects (1-2 years) and long-term effects (3-4 years) on functioning.

    The estimated end date for the study is May 3, 2033.

Who can join the trial?

6 criteria

  • The participant has experienced a first episode of psychosis and is currently using antipsychotic medication. Antipsychotic medication is used to help manage symptoms of psychosis.
  • The participant's psychotic symptoms have been in remission for 3-6 months. Remission means that the symptoms have improved or are not currently present.
  • The participant is between the ages of 16 and 60 years.
  • The participant understands the study and can provide written informed consent. This means they agree to participate after being informed about the study details.
  • The HAMLETT study is the only medical-scientific medication study in which the participant is involved.
  • The participant has a sufficient command of the Dutch language, meaning they can understand and communicate in Dutch.

Who cannot join the trial?

8 criteria

  • Patients who have not experienced a first episode of psychosis.
  • Patients who are not in remission, meaning their symptoms have not improved or stabilized.
  • Patients who are unable to follow the study guidelines, such as taking medication as directed.
  • Patients with other medical conditions that might interfere with the study or its results.
  • Patients who are pregnant or planning to become pregnant during the study period.
  • Patients who are currently participating in another clinical trial.
  • Patients who have a history of severe allergic reactions to the medications used in the study.
  • Patients who are unable to provide informed consent, meaning they cannot understand the study and agree to participate.
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Investigated drugs

Antipsychotic Medication This medication is used to help manage symptoms of psychosis, such as hallucinations or delusions. In the HAMLETT study, the focus is on understanding the effects of continuing versus stopping or reducing the dose of this medication in patients who have recovered from their first episode of psychosis. The study aims to see how these different approaches affect the patients' personal and social functioning over both short-term and long-term periods.

What is already known about the treatment

Antipsychotic Medication – This medication is typically administered orally in the form of tablets or capsules. It is currently well-established in medical practice and literature for managing psychosis, particularly after a first episode. The main therapeutic indication is to maintain remission in patients who have experienced a psychotic episode. At the molecular level, antipsychotics primarily work by blocking dopamine receptors in the brain, which helps to reduce symptoms of psychosis. They are classified pharmacologically as antipsychotic agents.

Investigated diseases

First Episode Psychosis – This condition refers to the initial occurrence of psychotic symptoms in an individual. Psychosis is characterized by a disconnection from reality, which may include hallucinations, delusions, and disorganized thinking. The progression of first episode psychosis can vary, with some individuals experiencing a single episode while others may have recurring episodes. During the remission phase, symptoms may significantly reduce or disappear, but the risk of relapse remains. Management often involves monitoring and support to maintain remission and prevent further episodes.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-518769-80-00Protocol codeNL6220204217Estimated enrolment444 patientsSponsorUniversitair Medisch Centrum Groningen

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