by Dr. Godofredo U. Stuart

You add another small prescription bottle to that too crowded medicine cabinet, the bottles nudge each other out of place, some tumbling out and down the sink. A quick date-inventory finds half of them in varying dates of expiry: a month, 6 months, a year. Tsk, tsk, tsk . . . what a waste! . . . and you're swiping the "expired" prescription drugs, over-the-counters, vitamins and supplements to the trash to make room for the new prescriptions.

What does the expiration date signify? Have the "expired" medications really lost potency? Do they really expire on the expiry dates? Are "expired" medicines harmful?

The "expiry date" or "expiration date" does not indicate a point when a medication loses potency and is no longer effective or becomes harmful. From the manufacturer, the expiration date is the final day it guarantees full potency and safety. It is an estimated date based on stability testing standards determined by the FDA—a date "required by law" generally set at 12 to 60 months after the '"manufacture date" of new medicines, usually embossed or printed on the original packaging.

For prescriptions filled by the pharmacist, it is usually dated a year after being dispensed from the original container. The "do not use after. . . " or "discard after. . . " dates are required by the Board of Pharmacy in 17 states. The manufacturer will not guarantee drug stability after the original bottle is opened. Therefore, the United States Pharmacopeia (USP), the body that sets the standard for pharmaceutical quality, recommends using the "beyond use" date. The beyond use date would never be later than the manufacturer's expiration date on the bottle. (3)

Drug companies admit there are no real data and that since some drugs expire earlier or faster than others, some manufacturers make a calculated guess at shelf life, then cut that in half to avoid legal consequences.

Potency
Studies have been done to test the stability of drugs beyond the expiration date. Stored under reasonable conditions, many drugs retain 90% of their potency for at least five years after the label's expiration date; sometimes, longer.

The FDA studied more than 100 drugs. It found that 90 percent of both prescription and over-the-counter medicines were perfectly good to use even 15 years (!) after the expiration date. The exceptions are insulin, liquid antibiotics and nitroglycerin.

The Shelf Life Extension Program (SLEP) undertaken by the FDA determined the actual shelf life of stockpiled military medications of over 3000 lots, representing 122 different drug products. Based on stability data, expiration dates on 88% of the lots were extended beyond the original expiration date for an average of 66 months. Of the 2652 lots, 18% were terminated due to failure. Some of the common drugs tested with no failures included amoxicillin, ciprofloxacin, diphenhydramine, and morphine sulfate injection. The extension on expiration dates on these products ranged from 12 to 184 months. (3)

The caveat in the SLEP study is that the military stockpile of medicines is kept in a climate-controlled, regulated area, not in a humid cabinet in a bathroom. (4)

Factors Affecting Degradation
While drugs may retain potency beyond expiration dates, eventually, they lose potency. Various factors influence degradation of drugs: formulation, storage, hydrolysis, oxidation and photo-degradation by light.

Formulation: Tablets, capsules, and unreconstituted syrups and injections have a shelf-life at room temperature of at least two years. However, once reconstituted, the syrups have a shelf-life of 14 days at room temperature, and injections should be used immediately. Some excipients or drug vehicles do not tolerate the heat and humidity of tropical climates.
Oxidation and photo-degradation: Protection from light may reduce the rate of oxidation of injectable solutions. Packaging may also protect against photo-degradation, i.e., use of amber glass or color film for blister-packing.
Temperature: The rate of chemical reactions doubles for every 10°C rise in temperature. Reconstitued amoxicillin syrup is stable at room temperature (25°C) for 14 days, longer if refrigerated.
Storage: Vaccines and insulin are usually stored in the refrigerator. Refrigerating or storing the medications in a cool place will help extend its potency for many years. However, most impoverished Third World countries do not have the luxury of refrigeration or cool storage places, and stability studies need to be done for drugs in the environ of prolonged heat and humidity. Read the labels for storage instructions, and avoid storing medications in bath and shower areas.

Of course, discard pills that have become discolored, cracked or splitting, turned powdery, or smell strong; capsules that have discolored or hardened; liquids that have turned cloudy or filmy; or tubes of creams that have hardened or turned liquid.

Loss of potency and harmfulness
And loss of potency does not translate to harmfulness. Other than a contested report associated with use of degraded tetracycline causing Fanconi's syndrome, there are virtually no reports of toxicity from outdated drugs. At most, they lose some potency.

Is the expiry date a mere marketing ploy? A commercial ploy that tags obsolesence to still potent drugs? Easy math. . . billions of drugs are regularly trashed and dumped because of expiration dates. Worldwide, the amount is staggering. Manufacturers claim for "product integrity." Consumers cry "profit!"

And for sure, the dilemma of expiry dates will continue to be cause for concern. How long ago did it "expire?" How much do time, heat and humidity contribute to a decline in potency? In many impoverished settings of Third World countries, patients don't have much of a choice. And when an "expired" drug works, it might have done so through its persisting potency, or through the powers of placebo or through a dose of tincture of time.

Some physicians feel comfortable doubling the time of use, from manufacture to expiration date. Some simply add two years to the expiry date.
In impoverished areas, where the choice is to treat with "expired" medications or NO treatment, the choice is a 'no-brainer.'

But if there is a choice, where potency is further brought to question because of weather and storage and cost not a problem, there are certain conditions where 100% absolute certainty of potency is preferable - for heart conditions, strokes, TIAs, and life-threatening infections. Aspirin potency may not be as important for the simple ache or headache as it would be in a TIA, stroke prevention or heart conditions. Antibiotic potency might not be as critical in the empiric treatment for suspected sinus infections as they might be for respiratory infections in the elderly and lung-compromised patients. Other medicines that should always be inside expiration dates are nitroglycerin, EpiPen and insulin.

So, when the urgency of clinical situation dictates, or when the conditions of storage are of concern, together with length of time beyond expiry date— until technology can gadget up some time-and-cost-effective way of determining drug potency—for both over-the-counter and prescription pharmaceuticals, opt for the new bottle or the new prescription.

Dr. Godofredo U. Stuart Jr.  
Updated November 2014

 

EXPIRY DATES OF DIABETIC TEST STRIPS: I have compared 3- and 6-month expired diabetic test strips to unexpired one and have found the results within range. I am interested in finding out if others have found similar results. The tewt strips are expensive, and there are a lot being trashed because of expiry dates. Please EMAIL comment.

From Dan A. / 3.27.10
2003 Test Strips
     I use AccuChek "compact" test strips. I got a BUNCH of these back in 2003. I still use these. I store them in a cool dark place in my house in factory sealed containers. I periodically check these against control solution and they are always accurate within 5-10% which is more then accurate enough for me.
      My old meter AccuChek Compact is happy to use them. The newer AccuChek Compact Plus notices that they are out of date and won't use them. I think these have a great shelf life because they include
anti-humidity stuff in the top of the lid on the sealed drums that these strips come in, so your mileage may vary with different strips/packaging.



Sources and Suggested Readings
(1)
Cortlandt Forum. July2005. Consultations.Susan Kashaf, MD. / MedLettDrugsTher.2002;44:93-94
Harvard Medical School: Family Health Guide

(2)
A GLIMPSE ON EXPIRY DATE OF PHARMACEUTICAL DOSAGE FORMS / A. PREM SWAROOP* and D.VARUN / PHARMANEST - An International Journal of Advances In Pharmaceutical Sciences Vol.2
(5 – 6 ) September – December -2011
(3)
Drug Expiration Dates - Are They Still Safe to Take? / Drugs.com
(4)
Are Expired Medications OK to Take? / One Expert Explains Why an Out-of-Date Aspirin Might Be Just Fine / Wall Street Journal
(5)
Prescription Drugs / Johns Hopkins Health Alerts
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