High-dose antipsychotic(s) can induce dopamine supersensitivity psychosis in schizophrenia patients. The precise relationship between a drug’s blood concentration and the occurrence of dopamine supersensitivity psychosis has not been established. We divided 36 patients with schizophrenia who had undergone treatment mainly with risperidone into two groups: one with normal metabolizing activity of CYP2D6 (n = 15), and the other with lower activity of its variant, CYP2D6*10 (n = 21). The patients’ blood concentrations of risperidone and 9-OH-risperidone were measured, and we compared the occurrence of dopamine supersensitivity psychosis episodes between the groups. There was no significant difference in any concentration of risperidone, 9-OH-risperidone, or active moiety between the groups although the with-CYP2D6*10 group had greater variabilities of these parameters compared to the without-CYP2D6*10 group. There was a lower rate of dopamine supersensitivity psychosis episodes in the without-CYP2D6*10 group (4/15, 26.7%) compared to the with-CYP2D6*10 group (11/21, 52.4%), but the difference was not significant. Although our findings were negative, largely because of the small sample size, these results suggest that (1) patients with an impaired functional allele of CYP2D6 may have higher concentrations of risperidone and its active metabolite and that (2) these patients may experience more frequent dopamine supersensitivity psychosis episodes.
aDivision of Medical Treatment and Rehabilitation, Center for Forensic Mental Health, Chiba University
bDepartment of Psychiatry, Chiba University Graduate School of Medicine
cHealth Care Management Center, Chiba University Hospital
dDepartment of psychiatry, Shoushin-kai Mobara Shinkei-ka Hospital
eDepartment of psychiatry, Shouhaku-kai Fujita Hospital, Chiba, Japan
Received 3 November 2018 Accepted 26 February 2019
Correspondence to Dr Nobuhisa Kanahara, Division of Medical Treatment and Rehabilitation, Chiba University Center for Forensic Mental Health, 1-8-1 Inohana, Chuou-ku, Chiba-shi, Chiba 260–8670, Japan, Tel: +81-43-226-2148; fax: +81-43-226-2150; e-mail: email@example.com