Physical stability of moisture‐sensitive tablets stored in a canister or as a unit‐dose

Background Knowledge about the long‐term stability of tablets outside the original container, e.g. as unit‐doses, is limited. This leaves the pharmacist with the dilemma of seeking improved patient safety by use of unit‐doses on one side, versus the lack of knowledge about the stability of the repackaged drug on the other. Aim To screen the physical stability of moisture‐sensitive repackaged tablets to identify those with the need for further chemical stability testing. Method The physical stability of commercially available tablets (16 products) was investigated after 6 months of storage at ambient conditions in canisters for unit‐dose production and after 3 months of storage as unit‐doses in a climate chamber at 25°C/60% relative humidity (RH). Changes in appearance, colour and mass were investigated in addition to changes in disintegration time, friability and resistance to crushing. Results The appearance and results of the physical tests for all products were acceptable and within the requirements of the European Pharmacopoeia, except for sodium valproate enteric‐coated tablets (Orfiril). These tablets were significantly altered after 3 months of storage as unit‐doses at 25°C/60% RH. However, when stored at ambient conditions the tablets complied with the tests. Conclusions The current study was a screening study limited to the investigation of the physical stability of a selection of moisture‐sensitive repackaged tablets. However, although the physical stability is acceptable, the chemical stability and dissolution rate may be altered. The physical tests outlined are simple but could be suitable for selecting candidates for further chemical stability testing.