Gender Differences in Clozapine Prescription in Australia

Abstract

Objective: This study investigated gender differences in clozapine prescription in Australia as a proxy measure of treatment resistant schizophrenia. Method: Patients (n=9383) were identified retrospectively from the Hospira ClopineConnect database ranging from October 1992 to September 2009. Data collected included patientsâ € ™ date of birth, gender, daily dose of clozapine and commencement date of clozapine. Results: The majority (69%) of patients on clozapine were male. The mean dose for males (433.6 mg, SD = 187.6 mg) was significantly higher than for females (376.1 mg, SD = 184.0 mg), p < 0.001. The mean dose per age group was higher for males than females in all age groups. The mean age at which female patients started clozapine was 36.3 years (SD = 12.5 years) and for male patients was 31.7 years (SD = 9.9 years), with the difference significant (p < 0.001). The male to female ratio of patients commencing clozapine was 2.6:1 below the age of 45, and 0.9:1 above the age of 45. The overall ratio of male to female patients was 2.2:1 which was higher than noted in other naturalistic clozapine databases in different regions of the world. Conclusions: Men are 2.2 times more likely to be prescribed clozapine and begin at an earlier age than females. The gap of several years in age of commencement of clozapine between males and females is comparable to a gap seen in age of first diagnosis of schizophrenia. This suggests that men are more likely to develop a more severe form of illness (treatment resistant schizophrenia) than women despite equal prevalence of schizophrenia. The gender difference in clozapine prescription is more marked in Australia when compared with other countries.