Kurland 1961.

Methods	Randomisation: random selection, no further details. Allocation: procedure not described. Blinding: double. Dispensed in unmarked capsules of #0 and #1 size coloured pink to mask all identifying consistencies and colours of the drugs. Duration: 6 weeks. Design: parallel. Location: single centre. Setting: inpatients.
Participants	Diagnosis: predominantly schizophrenia (clinical diagnosis). N = 69. Gender: n.i.. Age: mean 39 years. History: duration stable – n.i., duration ill – n.i., number of previous hospitalisations – n.i., age at onset – n.i., severity of illness – n.i., baseline antipsychotic dose – n.i..
Interventions	1. Perphenazine: flexible dose, allowed dose range 24 to 96 mg/day, mean dose 30.83 mg/day. N = 36.  2. Chlorpromazine: flexible dose, allowed dose range 300 to 1200 mg/day, mean dose 401.35 mg/day. N = 33.  Rescue medication: n.i..
Outcomes	Leaving the study early. Adverse effects: at least one adverse effect, movement disorders (MD) (at least one MD, akathisia, dyskinesia), adverse effects ‐ other (leucopenia, neurologic symptoms, rash, vasomotor episodes). Unable to use: Mental state: MSRPP (no SD), PSTS (no SD) Behaviour: PRP (no usable data, no SD).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Random selection, no further details.
Allocation concealment (selection bias)	Unclear risk	Procedure not described.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double. Dispensed in unmarked capsules of #0 and #1 size coloured pink to mask all identifying consistencies and colours of the drugs.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double. Dispensed in unmarked capsules of #0 and #1 size coloured pink to mask all identifying consistencies and colours of the drugs.
Incomplete outcome data (attrition bias) All outcomes	High risk	32 out of 36 from the perphenazine group left the study early (89%) of which 22% dropped out due to EPS. 26 out of 33 from the low‐potency group left early (79%). LOCF was applied.
Selective reporting (reporting bias)	High risk	MSRPP (no SD), PRP and PSTS (no usable data).
Other bias	Unclear risk	On the first two days of the study, participants received intramuscular medication, after that they were given oral mediations.