A matrixed approach to long-term stability testing of pharmaceutical products

A matrixed approach to long-term stability testing of pharmaceutical products is presented. The basic matrix design, suitable for testing three lots at one storage condition, may be extended to multiple product presentations or storage conditions. The design has full testing at the endpoints (0 and 36 months) and partial testing at the interim time points (3, 6, 9, 12, 18, and 24 months). The test points were selected with the assistance of a statistical search algorithm. The proposed matrix design provides a 37.5% reduction in analytical testing, while still permitting a reliable interim expiry estimate based on 12-month stability data. The expiration dating periods estimated using the matrixed approach are typically more conservative than estimates derived from a full-testing approach. A comparison of expiration dating period estimates for a metered-dose inhaler and capsule drug product using the matrixed and full-testing approaches is presented.