The New Straits Times, July 31,1995
Q: What are the hazards of using a drug product after its expiry date?
A: Before marketing, stability tests are performed on drug products in the same containers and closure systems in which they are to be sold. The expiry date identifies the period during which a preparation will be expected to maintain its labelled potency when stored under recommended conditions. The date is typically expressed in terms of month and year and should be interpreted as meaning the last day of the month that is listed.
Although many products exceed the minimum standard, it is generally accepted that a drug product should maintain 90 per cent (the United States Pharmacopoeia, USP, limit on deviation from labelled quantities) of its labelled potency. The expiry date should appear on the immediate container of the product, the outer retail package labelling, and the shipping canon.
Dry products that are reconstituted at the time of dispensing (for example, diluted with sterile water) should have expiry dates assigned to the reconstituted product.
If a product has been properly stored, the manufacturer can guarantee the potency of the preparation up to the time designated as its expiry date. After that date, however, the strength of the product is subjected to question and generally speaking, should never be used.
Inadvertent or intentional use of outdated drug products puts the patient at risk of receiving ineffective therapy if the active ingredients have deteriorated. The potency of outdated drug products cannot be guaranteed, and the active ingredients may, in rare instances, deteriorate into toxic compounds. In addition, the use of outdated drug products have been known to result in serious adverse effects.
In the early 1960s, the use of outdated tetracycline capsules was associated with the development of a particular type of kidney damage known as Fanconi syndrome. The condition results in urinary excretion of large amounts of glucose, amino acids, calcium and phosphate, which are normally retained by the kidney. Frequent urination, lethargy and progressive weakness are the initial symptoms. If the drug is discontinued, the symptoms subside over periods ranging from several weeks to almost a year.
Citric acid, which was in tetracycline products to enhance absorption, was found to promote the degradation of tetracycline into several toxic compounds. Tetracycline products have since been reformulated, and reports of Fanconi syndrome have not appeared for several years.
Therefore, it is advisable to check the expiry date every time you expiry date every time you buy a drug product and not to use drugs which have passed their expiry date.
