Diclofenac patches often, maybe always, have an expiration date. How does the efficiency of a diclofenac patch decrease as it approaches the expiration date?
Assume that the diclofenac patch is used to treat a lateral epicondylitis of the humerus, and that storage instructions were properly folowed (e.g., "Store patches in the envelope at room temperature at 77 degrees F (25 degrees C). Brief storage between 59-86 degrees F (15-30 degrees C) is permitted. Always reseal envelope after opening").
Some websites claim diclofenac patches are useless after the expiration date:
You will also need to throw away old patches after the expiration date has passed.
But it doesn't tell me to what extent the efficiency of a diclofenac patch decreases as it approaches the expiration date.