1. Possible design for a future study.

Method	Allocation: randomised ‐ clearly described generation of sequence and concealment of allocation. Blinding: double ‐ described and tested. Duration: long term. Setting: Inpatients and outpatients Design: Single phase, longer study duration.
Participants	People with schizophrenia or schizophrenia‐like disorder. N = Sample size obtained through power calculation. Age: any Sex: both History: History of tardive dyskinesia, fulfilling diagnostic criteria for tardive dyskinesia, stable on antipsychotic medication for at least 3 months.
Intervention	1.Pyridoxal Phosphate (vitamin B6), any dose 2. Placebo
Outcomes	Tardive dyskinesia scores measured using AIMS (primary outcome) Deterioration of tardive dyskinesia symptoms Any other adverse effects Discontinuation of pyridoxal phosphate (with reasons) Psychiatric symptoms score using a standardised rating scale (PANSS, BPRS) Pyridoxal phosphate dose Plasma pyridoxal phosphate level Quality of life Satisfaction with care

AIMS: Abnormal Involuntary Movement Scale
 BPRS: Brief Psychiatric Rating Scale
 PANSS: Positve and Negative Scale of Schizophrenia