Table 1.

Summary of studies evaluating time to commence clozapine among people with schizophrenia.

Authors	Study period and location	Sample size (n)	Time to commence clozapine (TCC) (SD; range)	Number of antipsychotics trialled prior to clozapine	Comments
Taylor et al. 2003	January 1990–April 2001, multiple IP units in South East London	100	5a,b (NA; 0-11.1)	5.5a	Significantly longer TCC was detected among those older than 30 years
Wheeler et al. 2008	1990–2004, CMHS, Auckland	917	9.7a,c (7.8; 0-43) 8c,d	3d	Longer TCC was noticed among older patients and patients of European ethnicity and to have started clozapine when government funding was restricted (1993-1998)
Harrison et al. 2010	1990-2007, all adult mental health patients prescribed clozapine at a public secondary care mental health service, as at March 31, Auckland	402	2.8a,e since 1999 (1.9; NA) 5.7a,e before 1999 (3.3; NA)	3.5a 3d	Mean TCC fell from 5.7 to 2.8 years since 1999 (when clozapine became widely available and nationally funded) In 2004-2007, mean TCC was less than 1 Trend toward reduced TCC in patients presenting more recently
Howes et al. 2012	January 2006–April 2010, IP and OP in South London and Maudsley NHS trust, United Kingdom	149	3.98a,b (4.14; 0-18.25)	3.9a 3d	The study describes a significant relationship between TCC and longer duration of illness
Alessi–Severini et al. 2013	May 2010–September 2010, OP attending clinics at Schizophrenia Program, Winnipeg, Canada	74	Male: 8.9c,d (NA) Female: 7.7c,d (NA)	3.3a	A trend toward earlier clozapine initiation was observed for those started on clozapine after 2005 with the mean TCC falling to 4.6 years
Najim et al.  2013	August 2004–October 2006, community hospital, semirural, South Essex, United Kingdom	42	5a,b (NA; 0.2-16.1)	4a 4d	Significantly longer TCC was noted in patients who were: Older than 30 years Diagnosed with treatment resistance before 1991 Treated before introduction of risperidone
Wheeler et al. 2014	1990-2007, IP and OP under the care of public secondary care mental health services in Auckland and Birmingham	Total: 664 Birmingham, 262 Auckland, 402	Birmingham 6.5a,e (3.8; NA) Auckland 5.3a,e (3.6; NA)	Birmingham: 4.3a Auckland 3.1a	Mean TCC was less than 1 in 2004-2007 in both UK and New Zealand cohorts
Üçok et al.2015	Period of study not available, outpatient units, Istanbul	162	2.42a,b (NA; NA)	2.4a	A shorter delay was found among the patients who were followed up since their first episode
Grover et al.  2015	January 2006–June 2014, both IP and OP at a tertiary care hospital, Chandigarh, India	200	1.93a,b (1.82; NA) 1b,d	3a	Increased TCC among those with longer duration of illness and age >20 years
Tang et al.  2016	April 2001–June 2012, State Psychiatric Hospital, Singapore	69f	1.10a,e (0.76; NA) 0.374a,b (0.52; 0-2.25)	3.4a 3d	Identified a shorter TCC among patients who were unemployed and economically inactive than those who were gainfully employed
Doyle et al.  2017	1995-2013,IP and OP who presented with a first episode psychosis between 1995 and 1999 at a CMHS in Dublin, Ireland	24	6.7a,e (3.5; 1-14)	4.85a	Identified underutilisation of clozapine for management of treatment-resistant schizophrenia The authors postulate several reasons for this and advocate for a better understanding of the barriers to prescribing clozapine

CMHS = Community Mental Health Service; IP = inpatients; OP = outpatients; NA = not available; TCC = time to commence clozapine in years.

^aMean.

^bMeasured from the establishment of treatment resistance.

^cMeasured from the onset of psychosis.

^dMedian.

^eMeasured from the first presentation to mental health service.

^fOf 69 patients using clozapine, 44 patients had established treatment resistance; n = 44 used to calculate TCC from establishment of treatment resistance.