Answer to Question #7000 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I have received conflicting information about the breakdown of potassium iodide (KI) over time or the half-life of the compound. Can you tell me if tablets that are past the "expiration date" on the label are still usable in the event of nuclear fallout or do they lose their effectiveness?
The Nuclear Regulatory Commission (NRC) has developed an FAQ page on the Internet dealing with this issue. The NRC distributes two strengths of KI—130 and 65 mg tablets. The shelf life of IOSAT 130 mg tablets is seven years and the shelf life of ThyroSafe 65 mg tablets is six years.
For states interested in extending the shelf life of KI, the Food and Drug Administration (FDA) has published guidance on shelf-life extension for the tablet form of KI. Extending the shelf life of KI tablets is possible due to the inherent stability of its chemical form. However, the tablets must be stored under the conditions specified by the manufacturer to be considered for shelf-life extension. In addition, this guidance only only intended for federal agencies and state and local governments that maintain KI stockpiles under the conditions specified by the manufacturer. The liquid formulation of KI also has a shelf life of five years. The extension guidance does not apply to this product form.
From FDA guidance on shelf-life extension, studies over many years have confirmed that none of the components of KI tablets, including the active ingredient, has any significant potential for chemical degradation or interaction with other components or with components of the container closure system when stored according to labeled directions. To date, the only observed changes during stability (shelf-life) testing have been the failure of some batches of KI tablets to meet dissolution specifications. Some tablets tested required slightly longer than the specified time to achieve dissolution. Even in the case of a failure of this sort, the product remains usable. In such cases, instructions can be provided to crush the tablets and mix them with a juice or other liquid prior to administration as suggested for emergency pediatric dosing.
Ronald E. Goans, PhD, MD, MPH