Stability of clozapine tablets repackaged in dose administration aids using repackaging machines

The use of dose administration aids in automated ward dispensing devices requires the repackaging of medications, which may impact their stability compared with the original manufacturer's packaging.

This study aimed to assess the physical and chemical stability of clozapine tablets for up to 84 days after repackaging.

A total of 900 tablets of clozapine 100 mg (Viatris) were repackaged and stored under five different conditions to conduct physical and chemical stability tests on days 0, 28, 56 and 84. The results were compared with control tablets in their original packaging. Visual inspections of tablet appearance were performed. Physical tests included assessments of mass uniformity, friability and resistance to crushing, following the standards of the European Pharmacopoeia 11th edition. The chemical stability was determined using ultra-high performance liquid chromatography with tandem-mass spectrometry detection (UHPLC-MS/MS) to measure clozapine concentration, N-desmethyl-clozapine, and monitor clozapine degradation to detect formation of any degradation products other than N-desmethyl-clozapine.

Visual examination showed changes in the appearance of tablets only in those stored under UV light. Mass uniformity met standards for all tablets over 84 days. None passed the friability test due to tablet cracking after tumbling. A gradual deterioration in tablet hardness was observed with the resistance to crushing test. In terms of chemical stability, N-desmethyl-clozapine was undetected in any of the tablets stored under all conditions, and the mean concentration of clozapine remained within the target range over 84 days.

N-desmethyl-clozapine was not detected and clozapine concentrations remained stable under all storage conditions. The tablets were compliant with the mass uniformity test in each condition. However, the tablets were cracked in the friability test and gradual deterioration in tablet hardness was observed. In the light of these results, the Vinatier Hospital pharmacy has chosen to establish a shelf life for clozapine tablets of 84 days.