This is a great question and it covers a topic in which there is not much transparency for the consumer, or patient in this case.
To start, let's define what an expiration date actually is.
Per The United States Pharmacopeia (USP), the official definition of the manufacturer’s expiration date is the: “Date beyond which ideally stored medications in the unopened manufacturer’s storage container or in most circumstances, the opened and intact manufacturer’s storage container, should not be used".
Since expired drugs should generally not be used (there are exceptions, however), when your prescription expires is of important consequence.
Prescription Expiring After Dispensing
There, unfortunately, is not much legislation in this area of pharmacy. Each state is responsible for setting their own guidelines and in most cases, they are woefully inadequate. It certainly is very likely that a patient could be dispensed medication that is readily nearing the expiration date.
The general rule is that the expiration date on the medication should be one year from the date of dispensing or the manufacturer’s expiration date, whichever comes first.
However, that isn't a legal requirement in most areas, but more of an unwritten rule (and also something many insurance companies require).
At the very least, there should be enough time to finish your prescription, when taken as directed, before it reaches the expiration date.
For one example, if a prescription of 90 tablets were dispensed on January 1st for '90 day supply', you can certainly assume that the manufacturer expiration date is at least until April 1st (90 days).
How Close To Expiration Can Prescriptions Be Dispensed?
While there are regulations regarding the labeling and dispensing of drugs with respect to their expiration, there really is no regulation on how close to that expiration date the drug can be dispensed.
The ethical thing for a pharmacy to do is obviously allow the patient enough time to complete their medication course prior to expiration but that certainly gets tricky when you are dealing with topical products like the tretinoin cream you mentioned in your question
Most states do NOT require the prescription label to state the actual manufacturer expiration date so there really is no visibility to how soon a medication would be expired.
Pharmacies typically just try to make sure that when they dispense a product, it’s good long enough for the patient to complete the full course of therapy.
Going back to your specific case, since you got a topical product in the manufacturer packaging, you know the actual expiration date.
While there is no law or regulation stating how "fresh" a medication needs to be when dispensed (as long as it is not expired) you certainly could and should request a product with an expiration date farther in the future and the pharmacy should accommodate that request in my opinion. They may not be legally required to do so, but to me, it seems the right thing to do.
The pharmacy you go to should be able to get a better-dated product from their wholesaler. They may not be able to guarantee a certain date, but in general, they would be alerted if any product they purchase had a shelf life of fewer than 6 months. Typically topical products such as tretinoin, when they are first produced, have an expiration date of 2-3 years, so you should be able to get a product with better dating.
SummaryMost states don't have laws specifying how far out the expiration date of your prescription product is, but you should be able to reasonably finish it prior to the listed expiration date if used as directed.
- Reference Standards United States Pharmacopeia