E-drug: Quality and stability of essential drugs
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Dear colleagues,
I am very new subscriber to E-drug, and I am not yet fully informed
about the issues that are being discussed through this forum. However,
I would like to comment on the drug stability question that was recently
raised.
Not long ago, I was researching the literature on the stability of
various dosage forms of prescription pharmaceuticals, especially the
stability of these compounds beyond their expiration date. There is
very little hard scientific data to support the conclusion that most
solid dosage forms are stable over long periods, especially under
conditions of high humidity and temperature.
For example, while the average drug content in pharmaceuticals does not
significantly change upon storage, changes in moisture content, tablet
hardness and enteric coating shrinkage have been shown to occur. These
changes can result in alterations in the release profile of the drug and
can have the affect of altering the blood concentration profiles and
oral bioavailability.
However, there are published articles to the contrary. The Medical
Letter had an article where the authors claimed that most drugs retain
70-80% of their potency for at least one to two years after the
expiration date, but they also noted "that published data are not
available and these are only estimates by Medical Letter consultants."
A Wall Street Journal article that supported the use of outdated
medication, especially in third world countries also noted that "Harmful
breakdown products may appear in a few drugs..." and "it would clearly
be foolish to take chances when treating serious disease..." and "all
drugs decompose over time."
When I looked specifically at the scientific literature for the
stability of an important and potent NSAID I found that the compound did
undergo chemical changes upon storage. These were the type of changes
that could the drug's absorption by the patient, and factors that affect
absorption can have profound effects on the clinical efficacy and
toxicity of the drug. Too rapid absorption can lead to toxicity and
injury of the patient and ineffective absorption can lead to a decrease
in therapeutic benefit.
When I looked at commonly used bactericidal disinfectants I found that
they too were reported to become unstable over periods of storage.
Chemical deterioration of these solutions may result in a diminished
ability to kill bacteria, fungi and viruses.
While I appreciate that a benefit/risk analysis of outdated or unstable
drugs might lead to the conclusion that the drug should be dispensed
anyway, I don't agree that generalizations about stability and drug
safety are warranted. I would recommend always being vigilant about the
quality of medications, for the sake of patient safety.
Best Regards,
Keith Yagaloff, Ph.D.
KEITH.YAGALOFF@roche.com
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