Yin Cao,1– 4 Qingrong Xia,1– 4 Jun Liang,1– 4 Jiequan Wang,1– 4 Feng Shan,1– 4 Biao Dai1– 4 

1Department of Pharmacy, Affiliated Psychological Hospital of Anhui Medical University, Hefei, People’s Republic of China; 2Department of Pharmacy, Hefei Fourth People’s Hospital, Hefei, People’s Republic of China; 3Psychopharmacology Research Laboratory, Anhui Mental Health Center, Hefei, People’s Republic of China; 4Department of Clinical Pharmacy, Anhui Clinical Research Center for Mental Disorders, Hefei, People’s Republic of China

Correspondence: Jun Liang, Department of Pharmacy, Hefei Fourth People’s Hospital, 316 Huangshan Road, Hefei, 230000, People’s Republic of China, Email amhcliangj@163.com

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.

Keywords: clozapine, blood drug concentration, schizophrenia, white blood cell count, neutrophil count, common cold