Abstract
OBJECTIVE: The present study aims to investigate the effect of common cold on the serum clozapine concentrations in hospitalized patients with schizophrenia. METHODS: A total of 65 schizophrenic patients with common cold receiving clozapine treatment were retrospectively enrolled. The demographic data, medication situation, clozapine concentration, and parameters of routine haematological and biochemical laboratory tests were obtained from the medical record system. The serum clozapine concentration and clozapine concentration/dose (C/D) ratios between the baseline period and cold period were compared by paired-sample t tests. Association between the changes in serum concentration and C/D ratios of clozapine and changes in white blood cell (WBC) and neutrophil (NE) counts was evaluated using Pearson correlation analysis. RESULTS: The serum clozapine concentration (t = -9.856, P < 0.001) and clozapine C/D ratios (t = -10.071, P < 0.001) were found to be significantly elevated in the cold period compared to the baseline period. Moreover, the changes in the serum clozapine concentration were found to be significantly elevated in female patients compared to male patients (t = -2.483, P = 0.017). Furthermore, changes in the serum clozapine concentration were positively correlated to the changes in WBC (r = 0.303, P = 0.014) and NE (r = 0.315, P = 0.011) counts. Similarly, changes in clozapine C/D ratios were positively correlated to the changes in WBC (r = 0.275, P = 0.027) and NE (r = 0.328, P = 0.008) counts. CONCLUSION: The serum clozapine concentrations in patients with schizophrenia during the common cold period were increased, which might by related to the elevated WBC and NE counts.