Distributed or stockpiled KI has a manufacturer-determined and FDA-acknowledged expiration date, so there is a need to replenish supplies periodically. Current FDA-approved formulations generally range in shelf-life from 2 to 3 years. It is well known that KI is extremely stable and should have a much longer shelf-life if stored under optimal conditions (for example, foil-wrapped for protection from air, moisture, heat, and light).
In March 2003, FDA (2003a) issued “draft guidance” for KI tablets shelf-life extension to provide guidance to state and local governments. It is a draft and is not officially available for implementation. There are two kinds of shelf-life extension: ordinary shelf-life extension with the manufacturer responsible for testing and DOD-sponsored shelf-life extension with FDA responsible for testing of stockpiled product.
Assay content and dissolution are the two specifications of concern in shelf-life consideration. None of the components of the KI tablets would be expected to significantly degrade or react with appropriate storage containers, but some KI tablets have failed to dissolute according to US Pharmacopeia (USP) specifications (75% within 15 min). However, the 75% dissolution was claimed to be achieved in a slightly longer period; this suggests that even if the USP requirement of 75% in 15 min were not reached, the product would be expected to be useful and provide appropriate protection. That is, the product should be considered as “usable”.
The March 2003 FDA draft document indicates that because KI is considered to be “very stable” when protected from moist air (KI is deliquescent and can release iodine and form iodate), additional testing “is probably unnecessary as long as the market package remains intact and continues to be stored under controlled conditions as described in the labeling.” A recommended protocol for shelf-life extension is also described with guidelines for accelerated stability testing with increased temperature and humidity) to achieve a 5-7-yr shelf-life designation. Recommendations for choosing a suitable laboratory for testing and the identification of batches qualified for extension and notification of expired batches are also discussed.