Prescription drugs can lose their effectiveness and may be dangerous if taken past their expiration date. The Harvard Medical School Family Guide says that nitroglycerin, insulin and liquid antibiotics may not retain their safety and potency. The Johns Hopkins Health Alert says that consumers should discard any pills that are discolored, powdery or have a strong odor, any liquids that are cloudy or filmy, or any creams that are hard or cracked within the tubes.
Chemical Changes
Chemical changes in a prescription drug can involve both the active pharmaceutical ingredient and the excipients, the other ingredients that hold the product together. According to "The Safety of Pharmaceutical Excipients," published by Elsevier, changes to the overall composition of the drug could cause the inert, or inactive, ingredients in the excipients to react with the active pharmaceutical ingredient, and generate impurities of the substances and alterations in the bioavailability of the drug, or how it will be assimilated in the body. Moreover, improper storage of the drug can cause chemical composition to change, such as change of color, smell and texture, and increase serious risks to patients, including toxicity to the liver.
Potency Changes
Prescription drugs lose their potency over time, especially when stored in nonrefrigerated environments. Potency loss in drugs taken for chronic conditions, such as asthma and heart disease, could be serious, especially if the medication is essential to stay alive. According to "Diabetes Care," insulin at the time of manufacture has a label potency of 100 units/ml and will lose less than 1 percent of its potency over 30 days at room temperature, and lose an accelerated rate of potency as the temperature increases. Furthermore, temperature changes, including exposure to heat or freezing temperatures, can affect the accuracy of dosing and blood sugar control from the drug. Antibiotics such as tetracyline are especially vulnerable to losing potency, becoming toxic over time and causing kidney damage if taken, says eMedExpert.
Microorganism Contamination
Sterility is critical for many prescription drugs, particularly aqueous based drugs, to prevent contamination by pathological microorganisms. Some vaccines, antiviral and respiratory drugs are available in lyophilized, or freeze-dried, powders that must be mixed with a liquid called a diluent and reconstituted before they can be administered to the patient. The Centers for Disease Control and Prevention says taht the reconstituted drug must be used by the expiration date since it is vulnerable to become contaminated with pathologic organisms that could infect the patient. Bacteria contamination can also occur when pre-filling syringes with drugs.
References
- Harvard Medical School Family Health Guide: Drug Expiration Dates - Do They Mean Anything?
- Johns Hopkins Health Alerts: How Long Do Medications Last?
- Elsevier: The Safety of Pharmaceutical Excipients
- Helium: The Dangers of Expired Drugs
- "Diabetes Care": How Long Should Insulin Be Used Once a Vial Is Started?
