Methods	Allocation: random, no further details. Blindness: double, no further details. Duration: 18 weeks. Design: parallel. Location: not reported.
Participants	Diagnosis: schizophrenia, non-response to or intolerance of three previous antipsychotic treatment trials. N=146. Age: mean clozapine=38.3 years, mean ziprasidone=41.6 years. Gender: 101 M, 45 F. History: duration of illness not reported, age at onset not reported. Setting: not reported.
Interventions	Clozapine: flexible dose, allowed dose range: 250-600 mg/day, mean dose=345.7 mg/day. N=73. Ziprasidone: flexible dose, allowed dose range: 80-160 mg/day, mean dose=130.4 mg/day. N=73
Outcomes	Leaving the study early: any reason. Global State: CGI. Mental State: PANSS total score, PANSS positive subscore, PANSS negative subscore, depression Calgary depression scale for schizophrenia. Adverse effects: cardiac effects (ECG), laboratory. Unable to use- PANSS positive, negative subscore (no data). CGI (no data). Laboratory parameters (no usable data).
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Random, no further details.
Allocation concealment (selection bias)	Unclear risk	No further details.
Blinding (performance bias and detection bias) Subjective outcomes	Unclear risk	Double, no further details. Whether blinding was successful has not been examined, but the compounds differ quite substantially in side-effects. This can be a problem for blinding
Blinding (performance bias and detection bias) Objective outcomes	Low risk	Objective outcomes such as laboratory measures or death are unlikely to have been much affected by problems of blinding
Incomplete outcome data (attrition bias) All outcomes	High risk	The overall attrition was 38.4%. Data on reasons for dropout were not available. The last observation carried forward method was used to account for people leaving the study early
Selective reporting (reporting bias)	High risk	Data were only presented as an abstract. Primary and secondary outcome data were reported incompletely
Other bias	High risk	The study was sponsored by the manufacturers of ziprasidone.