"Extended" (Alternate Day) Antipsychotic Dosing

• Status: Not yet recruiting
• Trial end date: 2026-09-30
• Target enrollment: 0
• Participant gender: All

Summary

The study wishes to examine whether "extended" antipsychotic treatment, in this case, antipsychotic treatment every other day, is as effective as daily treatment. It is also evaluating whether there may be differences in terms of side effects.

Participants will be randomly assigned to either the treatment as usual group (i.e., taking antipsychotic daily) or the extended dosing group (i.e., taking antipsychotic one day on, one day off). That means, like flipping a coin, there is a 50/50 chance that participants will continue on daily dosing of your antipsychotic or have it switched to every other day dosing.

This study will last for 1 year. Participants will be evaluated at the beginning and every two weeks during the first 6 months, with visits once every 4 weeks for the final 6 months. In total, participants will make 22 visits over 52 weeks to the investigator's office.

The investigators hypothesize that with ED, there will be no change in symptom severity but improvement in the frequency and severity of side effects, wellbeing, and functioning.

• Phase: Phase 4
• Accepts Healthy Volunteers?: No

Details

• Lead Sponsor: Centre for Addiction and Mental Health
• Treatments: Olanzapine; Risperidone

Criteria

Inclusion Criteria:

(i) A primary diagnosis of a Schizophrenia Spectrum or Other Psychotic Disorder as defined by the DSM-5 diagnosis and confirmed by the MINI (Version 7.0)

(ii) age 18 or older

(iii) female participants of childbearing potential must be using a reliable method of contraception and have a negative pregnancy test at the time of enrolment and must, in the investigator's opinion, practice a clinically accepted, reliable method of contraception during this study. Male participants must not father a baby during their time in the study

(iv) ability to communicate in English

(v) capacity to provide written, informed consent, as assessed using the MacCAT-CR at time of consent

(vi) stabilized as outpatients with a single oral AP (risperidone or olanzapine*) ≥3 months i. On a prescribed risperidone dose of between 1-6mg, or a prescribed olanzapine dose of between 5-20mg

(vii) evidence of adherence with current AP treatment

Exclusion Criteria:

(i) no exposure to a depot AP within 1 year (i.e., no depot AP injection within the last year)

(ii) no current diagnosis of substance use disorder according to DSM-5 criteria (verified though the MINI and Drug History Questionnaire (DHQ)77) and a drug screen

(iii) no ECT within the last 3 months

(iv) pregnancy or lactation

(v) no neurological condition (dementia including Alzheimer's disease, multiple sclerosis, epilepsy, stroke, or traumatic brain injury)

(vi) no allergy to the study drugs and their excipients

(vii) no allergy or intolerance to lactose