Clozapine and desmethylclozapine: correlation with neutrophils and leucocytes counting in Mexican patients with schizophrenia

Abstract

PurposeThe aim of present study is to measure plasma clozapine (CLZ) and N-desmethyl clozapine (DMC) as biomarkers to correlate drug concentrations with the appearance of preclinical adverse hematic effects.MethodsA high-performance liquid chromatographic method, using a diode-array (ultraviolet) detector, was validated to obtain reliable concentrations of CLZ and DMC, its main metabolite, in plasma of 41 schizophrenic patients taking CLZ. Blood neutrophils and leucocytes counting were concurrently assessed as a proxy to subclinical adverse reactions.ResultsThe analytical method employed was linear, reproducible, and stable to measure concentrations of CLZ between 30 and 1000 ng/mL, while 12.5–560 ng/mL of the metabolite. The method allowed us to correlate CLZ plasma concentrations, the time taking CLZ and CLZ dose as determinants of neutrophils’ counting with a R2 = 0.447, using a multiple regression analysis model. Likewise, the correlation of leucocyte counting vs CLZ plasma levels and CLZ time, showed a R2 = 0.461. DMC correlated significantly with both neutrophils and leucocytes counting, but was excluded from the regression when CLZ concentration was included in the model. Finally, no other hematological adverse reactions were recorded. One patient presented a cardiovascular complication. The negative correlation between clozapine and neutrophil count observed in patients, suggest that CLZ itself, but not DMC, could be related to hematologic side-effects.ConclusionThe findings of this study, demonstrate for the first time, that plasma levels of CLZ and time taking the drug are independent determinants of blood neutrophils and leucocytes, so the monitoring of plasma CLZ may be useful in the clinic practice to determine safe dosing of the drug.

Clozapine metabolism is associated with Absolute Neutrophil Count in individuals with treatment-resistant schizophrenia

“…Another noteworthy difference is that the daily clozapine dose prescribed is substantially different between the two cohorts, as inferred from a comparison of the study descriptive statistics. In our study average clozapine doses were 348 mg/day for males and 313 mg/day for females, while Vaquero-Baez et al (2019) reported average doses of 223 mg/day for males and 105 mg/day for females (t-test p male =1.31 × 10 −10 ; p female =1.43 × 10 −6 ). There was also a significant difference in the average time that the cohorts had been on treatment with clozapine, upwards of three years in our study with 3.26 years for males and 3.21 years for females, and fewer than one year (Vaquero-Baez et al, 2019) with 10 months for males and 6.5 months for females (t-test p male =5.9 × 10 −3 ; p female =6.18 × 10 −16 ).…”

“…Mirroring the approach of Vaquero-Baez et al (2019), Pearson’s correlation statistics are reported in Table 3 . Clozapine concentration was significantly associated with ANC in this analysis (r=-0.16; p = 0.019), whilst norclozapine, time on clozapine and daily dose were not.…”

“…Firstly, the original study was conducted in Mexico, and the individuals recruited are likely of different ancestry (Ruiz-Linares et al, 2014) to our cohort that was recruited in the UK and made up only of those of European ancestry as inferred from genetic analyses. It cannot be ruled out that the work of Vaquero-Baez et al (2019) has uncovered a population- or ancestry-specific effect, although no literature exists at this time to support this. An increased prevalence of neutropenia has been found in individuals with schizophrenia of African ethnicity (Kelly et al, 2007), and “benign” (constitutional) neutropenia rates vary widely based on genetic ancestry (Haddy et al, 1999; Legge et al, 2019), but no specific risk has been found in Mexican, Latino or Native American people to date.…”

“…As a direct replication of Vaquero-Baez et al (2019), Pearson’s correlations were computed to assess the bivariate relationships between plasma clozapine concentration, plasma norclozapine concentration, time on clozapine treatment, daily clozapine dose and ANC. Expanding on those analyses, multivariate linear regression models were used to assess the association between plasma clozapine concentration (mg/L) and ANC (cells/mm 3 ) accounting for eight additional covariates: norclozapine plasma concentration (mg/L), daily clozapine dose (mg), time on clozapine treatment (days), time between clozapine concentration measurement and ANC measurement (days), time between clozapine dose and blood sampling (hours), age (years), age 2 and sex.…”

Integrative Genomic–Epigenomic Analysis of Clozapine-Treated Patients with Refractory Psychosis

“…Blood samples were taken at steady state (i.e., at week 18 of treatment). The preparation of plasma samples was carried out as previously reported [ 27 ], and plasma concentrations of CLZ and its main metabolite (ng/mL), N -desmethylclozapine or nor-clozapine (NCLZ), were determined by HPLC, and the metabolic ratios of CLZ/NCLZ were also calculated.…”