Stability of Clozapine Stored in Oral Suspension Vehicles at Room Temperature
Clozapine is indicated for the management of symptoms in treatment-resistant schizophrenia. This drug is available as 25-mg and 100-mg uncoated tablets. A liquid formulation is required for patients who cannot or will not take tablets, but no commercial oral liquid exists. The stability of a 20 mg/mL clozapine suspension prepared by suspending crushed tablets in an oral solution referred to as Guy’s pediatric mixture has been described. Guy’s pediatric mixture contains sucrose, carboxymethylcellulose, methyl hydroxybenzoate, and propylhydroxybenzoate and is not commercially available. The clozapine suspension prepared with this vehicle demonstrated no change in concentration when stored for 18 days at room temperature. However, preparation of Guy’s pediatric mixture is time-consuming and tedious. Various other vehicles are available, including some products that may be purchased commercially, but the stability of clozapine in these vehicles is unknown.
The objective of this study was to evaluate the stability of a 20 mg/mL clozapine suspension in 6 different suspending vehicles — Ora-Sweet, Ora-Plus, a 1:1 mixture of Ora-Sweet and Ora-Plus, the suspending vehicle used by the Hospital for Sick Children, simple syrup, and Guy’s pediatric mixture — when stored for 9 weeks at room temperature.