Stabilization time of serum Clozapine and N-desmethylclozapine extended by refrigerated storage blood samples at a fixed volume

Objective To explore the optimal storage methods to maintain serum clozapine (CZP) and N-desmethylclozapine (N-CZP) concentration in a long-term stablility. Methods Ten fresh clinical blood samples were collected, and each sample's serum was separated at volume of 0.5 ml into five pieces of 10 ml conic glass cen-trifuge tubes with cocks; then CZP and N-CZP were beth assayed with HPLC in samples collected on sampling day, stored at 4 ℃ and -20 ℃ for 12 weeks and 24 weeks,respectively. Results There was no significant difference in CZP among samples stored at 4 ℃ for 12 weeks[(525.1±124.3) μg/L] ,at -20 ℃ for 12 weeks[ (535.5± 126.7) and 24 weeks[ (532.5±126.7) μg/L] ,as well as collected on sampling day[(542.7±135.0) μg/L] (P>0.05); There was also no significant difference in N-CZP among samples stored at -20 ℃ for 12 weeks [(226.2±50. 7) μg/L] and 24 weeks[ (224.9±44.8) μg/L] and collected on sampling day[(236.9± 66.6) μL] (P>0.05). Conclusion CZP and N-CZP concentration would be maintained stable within 24 weeks under the refrigerated storage temperature of -20 ℃ at a fixed volume. Key words: Clozapine;  N-demethylclozapine;  Fixed quantity;  Refrigerated storage