Answer to Question #7000 Submitted to "Ask the Experts"

Category: Radiation Accidents

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

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 11 January 2008. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.