Kong 2001.

Methods	Allocation: unclear. Blindness: unclear. Duration: 8 weeks. Design: multicentre. Setting: inpatients.
Participants	Diagnosis: schizophrenia (CCMD‐2‐R)*. N = 60. Age: < 42 years. Sex: 38 male and 22 female. History: partial response to clozapine, but criteria not clearly specified.
Interventions	1. Clozapine plus risperidone: clozapine mean dose 400 mg/day and risperidone mean dose 4 mg/day to 6 mg/day. SDs not provided. N = 30. 2. Clozapine plus sulpiride: clozapine mean dose 500 mg/day and sulpiride mean dose 800 mg/day to 1200 mg/day. SDs not provided. N = 30.
Outcomes	Clinically significant response: 20% to 50% reduction PANSS total. Clinical response: mental state (PANSS total, PANSS positive, PANSS negative). Adverse effects: weight gain, hypersalivation. Leaving the study early. Unable to use: Adverse effects: TESS score.
Notes	*It is unclear whether patients with schizoaffective disorder were enrolled.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information.
Allocation concealment (selection bias)	Unclear risk	Insufficient information. Allocation done by hospital number so possibly not concealed.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient information.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No one left early.
Selective reporting (reporting bias)	Unclear risk	No protocol available.
Other bias	Unclear risk	We could not rule out the potential for other bias.