To assure that a drug meets standards of identity, strength, quality, and purity before use, the US Code of Federal Regulations (CFR) (Title 21, Part 211.137) sets forth the conditions under which an expiration date must be listed on drug product labels. With few exceptions, companies must list an expiration date on the immediate container and any outer packaging if the date is not legible through the outer packaging. When single-dose containers are packed in individual cartons, the expiration date may appear on the carton instead of the immediate container. Unfortunately, the CFR does not specify how expiration dates must be expressed. Thus, confusion sometimes occurs.

For example, one pharmaceutical company listed "JN05"as the expiration date on a suppository package label; but does "JN"mean "January"or "June"? Another company used an atypical abbreviation for April, "AL,"and produced a code which read "AL 05,"meaning "April 2005."Yet another company's poliovirus vaccine (inactivated) listed an expiration date of "06 MAR 04."Practitioners became confused, however, as to whether it meant the drug expired on March 6, 2004, or March 4, 2006.

In the last case, such problems did not arise until 2001. For example, when "99"appeared with "05,"it was clear that the year of expiration was 1999. Before 2001, the year could not be mistaken as a day; now, the numbers used for the day and year may overlap until the year 2032.

A medication error has occasionally resulted from a misinterpreted expiration date. In one instance, a night nurse thought that vials of magnesium sulfate had expired. The expiration date was listed as "1-06,"but the product lot number, 2002, appeared right before the expiration date. Not knowing that "2002"was a lot number, the nurse thought the drug expired on 1/06/02. Treatment was delayed while the nurse attempted to obtain a new vial.

Similar problems may occur with OTC products. Under the CFR, expiration dates for OTC products are not enforced if their labeling does not bear dosage limitations and if they are stable for at least 3 years. When they do appear, expiration dates may be difficult to decipher. For example, one company's packaging of one of its liquid nutritional supplements (a medical food supplement) did not list an expiration date, but rather, used a 4-digit code for the month and year of production (ie, "0504"for "May 2004"). This had been misinterpreted as an expiration date. Although not explained in the packaging, the user was supposed to add 270 days to the production date to determine the expiration date.

In the 2005 US Pharmacopeia (USP)-National Formulary General Notices (pg 11), expiration dating is addressed in a way that might facilitate the FDA's ability to clarify the above ambiguity. Under the section Expiration Date and Beyond-Use Date, it states: "The label of an official drug product or nutritional or dietary supplement product shall bear an expiration date. All articles shall display the expiration date so that it can be read by an ordinary individual under customary conditions of purchase and use. The expiration date shall be prominently displayed in high contrast to the background or be sharply embossed and easily understood (eg, ?EXP 6/89,'?Exp June 89,'or ?Expires 6/89')."The Consumer Healthcare Products Association has also published "Voluntary Codes and Guidelines of the OTC Medicines Industry." The guidelines offer specific procedures related to the display, location, and legibility of expiration dates; expiration statements that are understandable to consumers (eg, "Exp 6/99,""Expires 6/99"); the avoidance of packaging features that might interfere with their legibility (eg, end seals on shrink-wraps); and emerging technologies for the application of expiration dating (eg, improved debossing techniques, advances in ink printing). Clearly, standards are needed for expressing dates in a uniform sequence that does not confuse the practitioner or the patient.

Ms. Needleman is a medication safety analyst with Med-E.R.R.S.

Med-E.R.R.S., a wholly owned subsidiary of the Institute for Safe Medication Practices (ISMP), works with the pharmaceutical industry to help avoid errors related to packaging, labeling, and nomenclature. The reports described in this column were received through the USP-ISMP Medication Errors Reporting Program (MERP). Errors, close calls, or hazardous conditions may be reported on the ISMP ( or USP ( Web sites. They may be communicated directly to ISMP by calling 800-FAIL SAFE or via e-mail at