The investigators are going to observe if add-on of n-acetylcysteine (NAC) 1200 or 2400 mg/d during tapering of antipsychotics in patients with remitted psychosis can help to reduce the pre-requisite of stabilization to 3 months (compared to the 6 months prerequisite of a previous Guided Antipsychotic Reduction to Minimum Effective Dose (GARMED) trial,) smoothly, without increased risk of relapse or frequency of adverse events compared to the 2-year results of the GARMED trial
Trial procedure * Pretreatment: more instructions were delivered regarding the extent and the tempo of dose reduction, warning signal of relapse, timing to call for help if in need to resume rescue dose, and a shared decision-making process during tapering. Pre-treatment of NAC 1200 mg/d will be given for 1-2 weeks and then titrated up to 2400 mg/d to test tolerability. Patients will stay at either dose throughout the remaining of the course as preferable. * Dose tapering schedule: In the beginning, no more than one-quarter of the baseline antipsychotic dose will be reduced at a time. Patients need to be monitored every 4 weeks (or 1 month) by phone or in person. If they can maintain stabilized for 12 weeks (or 3 months) in a reduced dose, they can take next tapering of no more than one quarter of their current dose again, yielding 9/16 (3/4x3/4) of baseline dose. The subsequent dose reduction will be a reiteration of the previous step, cutting off one-quarter of the current dose following the formula (3/4) powered by n, rather than cutting off another 1/4 of the initial dose. The processes will be reiterated for 4 steps for one year. * Conditions during tapering: Noteworthily, when the patient is eligible to consider next dose reduction, he or she is empowered to take shared decision-making as they might opt to stay at their current dose for a more extended time for any reason. Patients can reach the study team during the course whenever they felt unsure if any relapse sign might be re-emerging. As needed use of benzodiazepines or hypnotics will be allowed to help control suspected signs of relapse. Patients will be supervised to stay at current dose for a longer term or even re-escalate to previous higher dose if any sign of suspected relapse re-emerges, and then will be closely monitored if their symptoms can be stabilized within 2 weeks. * Defining relapse: If a patient's recurrent psychotic symptoms cannot be controlled (any PANSS score \> 3 in P1, P2, P3, G5, or G9) within 2 weeks under an antipsychotic dose equal to their baseline dose, the patient will be designated as having a relapse. * Practicability of dosing: The actual dose taken would not always be precisely the number calculated by the formula (3/4)n, as it was impractical to cut off a quarter or even smaller piece of a tablet for daily dosing. Several versions of intermittent or irregular dosing schedules have been generated to meet the needs. * Extent of dose reduction: The percentage of doses reduced at a designated time point will be calculated by the following formula: \[1- (current dose)/(baseline dose)\]x100%.
regular dose or high dose add-on
Relapse rate (%)
If a patient's recurrent psychotic symptoms cannot be controlled (any PANSS score \> 3 in P1, P2, P3, G5, or G9) within 2 weeks under an antipsychotic dose equal to their baseline dose, the patient will be designated as having a relapse
Time frame: 1 year
Extent of dose reduction (%)
The percentage of doses reduced at a designated time point will be calculated by the formula: \[1- (current dose)/(baseline dose)\]x100%
Time frame: 1 year
Clinical severity: symptoms
Positive and Negative Syndrome Scale (PANSS) (1 to 7, 1: normal; 7: profound severity)
Time frame: 1 year
Clinical severity: global
Clinical Global Impression of Severity (CGI-S) (1 to 7, 1: no illness; 7: most severe)
Time frame: 1 year
Personal and Social Functioning
Personal and Social Performance scale (PSP) (0-100, worst to best)
Time frame: 1 year
Self-report of subjective wellbeing
EuroQoL-5D visual analogue scale (EQ-5D-VAS) (0-100, worst to best)
Time frame: 1 year
Self-report of Quality of Life
Mandarin Chinese version of the WHOQOL-BREF (1\~5, 1: very dissatisfied; 5: very satisfied)
Time frame: 1 year
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Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
20